Effect Of Alcohol Blend And Fumigation On Regulated And Unregulated Emissions Of Ic Engines—a Review.pdf

Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Contents lists available at ScienceDirect

Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser

Effect of alcohol blend and fumigation on regulated and unregulated emissions of IC engines—A review Meisam Ahmadi Ghadikolaei n Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

art ic l e i nf o

a b s t r a c t

Article history: Received 9 August 2015 Received in revised form 25 October 2015 Accepted 17 December 2015 Available online 8 January 2016

In recent years, the effect of alcohols as an alternative fuel on emissions of IC engines has been investigated in a lot of experimental works. However there is a lack of a comprehensive review study about the definition and type of emissions (regulated and unregulated emissions) and alcohols and the influence of alcohols on unregulated emissions of IC engines. Therefore, this literature review study is presented. In the current literature review work, two sections are provided. A brief detail of the effect of alcohols (methanol and ethanol) in blended and fumigation modes on regulated emissions in IC engines is presented in the first section. And the second section (main section of this work) is a comprehensive review part of the literatures related to the effect of methanol and ethanol in blended and fumigation modes on unregulated emissions in IC engines. In this literature review work, a wide type of IC engines, such as SI and CI engines and motorcycles were collected with different operation conditions. Different percentages of alcohol blend and fumigation were summarized to get informations about the effect of alcohol on regulated and unregulated emissions of IC engines. For regulated emissions, it was found that

Keywords: IC engines Methanol Ethanol Blend Fumigation Regulated and unregulated emissions

Abbreviations: °C, degree celsius; mm, micrometer; 1-D, one dimension; AEA, Atomic Energy Authority; AFR, air/fuel ratio; Al, aluminum; ALD, aldehydes; ASTM D 2533, Standard Test Method for Vapor–Liquid Ratio of Spark-Ignition Engine Fuels; ASTM D 4814, Standard Specification for Automotive Spark-Ignition Engine Fuel; ASTM D 5188, Standard Test Method for Vapor–Liquid Ratio Temperature Determination of Fuels; B(a)P, benzo(a)pyrene; BALB/c, laboratory-bred strain of the house mouse; BDL, below the detection limit; BTDC, before top dead center; BTEX, benzene, toluene, ethylbenzene and o-xylene, m/p-xylenes; BTX, benzene, toluene, xylene; Bu, butanol; C1
, chloride; C10H8, naphthalene; C12H10, acenaphthene; C12H8, acenaphthylene; C13H10, fluorine; C14H10, phenanthrene; C14H30, diesel; C14Hl0, anthracene; C16H10, fluoranthene and pyrene; C18H12, benzo[a]anthracene and chrysene; C20H12, benzo[j]fluoranthene, benzo[k] fluoranthene, henzo[a]pyrene and henzo[e]pyrene; C22H12, benzo[ghi]perylene and indeno[1,2,3-c,d]pyrene; C22H14, dibenz[a,h]anthracene; C2H12, benzo[b]fluoranthene; C2H2, ethyne; C2H4, ethene; C2H5OH, ethanol; C2H6O, ethanol; C4H6, 1,3-butadiene; C6H6, benzene; C7H16, gasoline and N-heptane; C7H8, toluene; C8H10, xylene; Ca, calcium; CAD, Crankshaft angle degrees; CARB, California Air Resources Board's; CECERT, Center for Environmental Research and Technology; CFR, Code of Federal Regulations; CH3CH2OH, ethanol; CH3OH, methanol; CH4, methane; CI, compression ignition; CO, carbon monoxide; CO2, carbon dioxide; CR, compression ratio; Cu, copper; DC, direct current; DI, direct injection; DISI, direct injection spark ignition; DI, Drivability Index; DMCC, diesel/methanol compound combustion system; DME, dimethylether; DMF, dimethylfuran; DNPH, di-nitro-phenyl-hydrazine; DOC, diesel oxidation catalyst; DOE, Department of Energy; DOHC, double overhead camshafts; DPFs, diesel particulate filters; DPM, diesel particulate matter; E, ethanol; ED95, 95% ethanol and 5% ignition enhancers; EGR, exhaust gas recirculation; EN228, EU fuel specifications for sulfur content (50 ppm); EPA, Environmental Protection Agency; ETH, ethanol; EtOH, ethanol; EU, European Union; EUDC, extra-urban driving cycle; FAO, Food and Agriculture Organization; FBP, final boiling point; Fe, iron; FFV, flexible fuel vehicle; FID, flame ionization detection; ft, foot; FTIR, Fourier transform infrared spectroscopy; FTP, Federal test procedure; g, gram; GC–MS, gas chromatography mass spectrometer; GDI, gasoline direct injection; GDP, gross domestic product; h, hour; H2, hydrogen gas; HC, hydrocarbon; hp, horse power; HPLC, high performance liquid chromatograph; IARC, International Agency for Research on Cancer; IBP, initial boiling point; IC, internal combustion; IDI, indirect injection; IEA, International Energy Agency; IHC, individual hydrocarbons; ILUC, in-direct land use change; IMR, ion molecule reaction; ISAF, International Symposium on Alcohol Fuels; K, Kelvin; km, kilometer; KPa, kilo Pascal; KW, kilowatt; L, liter; LabVIEW, Laboratory Virtual Instrument Engineering Workbench; lb, pound; LEV, low emission vehicle; LHV, lower heating value; LPG, natural gas and motorgas/petroleum gas; M, methanol; MEK, methyl ethyl ketone (butanone); MeOH, methanol; MF, methlyfuran; Mg, magnesium; mL, milliliter; mm, millimeter; MMT, million metric tons; MON, Motor Octane Number; MPa, mega Pascal; MTBE, methyl teriary buthyl ether; MTO, methanol to olefins; MTP, methanol to propylene; MY, model year; N/D, no data; N2O, dinitrogen oxide; NA, naturally aspirated; Na, sodium; NDIR, Nondispersive Infrared Detection; NEDC, New European Driving Cycle; ng, nano gram; NH4 þ , ammonium; Nitro, nitrogenate; nm, nanometer; N m, Newton meter; NMHC, non-methane hydrocarbons; NMOG, non-methane organic gases; NO, nitrogen oxide; NO2
, nitrite; NO2, nitrogen dioxide; NO3,, nitrate; NOX, nitrogen oxides; O3, ozone; OECD, Organization for Economic Co-operation and Development; OEM, original equipment manufacturer; Oxy, oxygenated; P, phosphorus; PACs, polycyclic aromatic compounds; PAHs, polycyclic aromatic hydrocarbons; PAN, peroxyacetyl nitrate; PDPCVS, positive displacement pump-constant volume sampling; PFI, port fuel injection; PM, particulate matter; ppm, parts per million; Psi, pounds per square inch; RFA, Renewable Fuels Association; RON, research octane number; rpm, revolutions per minute; RVP, Reid vapor pressure; S, sulfur; SEPA, State Environmental Protection Administration; SEPA, Swedish Environmental Protection Agency; SGC, summer grade commercial; SGDI, spray-guided direct-injection; Si, silicon; SI, spark ignition; SIDI, spark ignition direct injection; SO2, sulfur dioxide; SO4
2, Sulfate; SOA, secondary organic aerosols; SOF, soluble organic fraction; SULEV, super-ultra-low emission vehicle; TD, thermal desorbed; TDC, top dead center; THC, total hydrocarbons; TPM, total particulate matter; TWC, three-way catalyst; UDC, urban driving cycles; UK, United Kingdom; ULP, unleaded petrol; ULSD, ultra-low-sulfur diesel; US, United States; USA, United States of America; USEPA, United States Environmental Protection Agency; V/L, vapor/liquid; VERL, Vehicle Emissions Research Laboratory; VL, vapor lock; VOCs, volatile organic compounds; Vol%, volume percent; VT, variable temperature; VVT, variable valve timing; WC, water cooled; Wt, weight; Zn, zinc n Tel.: þ 989355087335, þ 852 97193237. E-mail address: [email protected] http://dx.doi.org/10.1016/j.rser.2015.12.128 1364-0321/& 2015 Elsevier Ltd. All rights reserved.

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

1441

application of alcohols as alternative fuels in fumigation mode in IC engines led to reduction of NOX and CO2 in most tests and PM in all cases. However, an increase of CO and HC was observed with using alcohols in fumigation mode in most cases. It is noticeable that a diverse effect of alcohol application in blended mode compared to fumigation mode on regulated emissions was recorded in considerable tests except PM. For unregulated emissions, it was found a reduction of BTEX (benzene, toluene, ethylbenzene and o-xylene, m/p-xylenes) in blended mode in most cases, polycyclic aromatic hydrocarbons (PAHs) in blended mode in major experiments and 1,3-butadiene, ethyne and ethene in both modes in all tests with using alcohols compared to fossil fuels. On the other hand, it was seen an increase of unburned ethanol and methanol and total carbonyls in both modes in all tests. And, an increase of formaldehyde and acetaldehyde which are the predominant carbonyls in the exhaust for vehicles was recorded in most and major experiments, respectively for both modes. In addition, soluble organic fraction (SOF) had an increase in both modes in major tests. And an increase of benzene, toluene, xylene (BTX) was observed in fumigation mode in significant tests. & 2015 Elsevier Ltd. All rights reserved.

Contents 1. 2.

3.

4. 5.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1442 Alcohol as a supplementary fuel in IC engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1443 2.1. Physicochemical properties of alcohol as a fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1443 2.2. Fundamental aspects of alcohol chemistry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1444 2.2.1. Ethanol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1444 2.2.2. Methanol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1446 2.3. Differences of physicochemical characteristics of methanol with ethanol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1449 2.4. Overview of fossil and alcohol fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1450 2.5. Alcohol productions and economics in the world . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1450 2.5.1. Ethanol productions and economics in the world . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1450 2.5.2. Methanol productions and economics in the world . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1450 Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1452 3.1. Regulated exhaust emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1452 3.1.1. Particulate matter (PM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1452 3.1.2. Carbon monoxide (CO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1452 3.1.3. Nitrogen oxides (NOX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453 3.1.4. Hydrocarbons (HC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453 3.2. Unregulated exhaust emissions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453 3.2.1. Alcohols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453 3.2.2. Alkenes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453 3.2.3. Alkyl nitrites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453 3.2.4. Monoaromatics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1454 3.2.5. Particulate emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1454 3.2.6. Peroxvacetyl nitrate (PAN). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1454 3.2.7. Polycyclic aromatic hydrocarbons (PAHs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1454 3.2.8. Nitro-PAHs and Oxy-PAHs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1455 3.2.9. Carbonyl compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1455 3.2.10. Nitrogen dioxide, (NO2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1456 3.2.11. Quinones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1456 3.2.12. Sulfur dioxide (SO2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1456 3.2.13. Metal oxides and metallic PM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1456 3.2.14. Nitrous oxide (N2O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1456 3.2.15. Dioxins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1456 Results of regulated emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1462 Results of unregulated emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1462 5.1. G. Karavalakis and co-workers (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1462 5.1.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1462 5.1.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1462 5.1.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1462 5.1.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1464 5.2. Ch. Wang (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1464 5.2.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1464 5.2.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1465 5.2.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1466 5.2.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1466 5.3. Li and co-workers (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1466 5.3.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1466 5.3.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1466 5.3.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1467 5.3.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1468 5.4. G. Karavalakis and co-workers (2012) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1468 5.4.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1468

1442

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

5.4.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5. H.H. Yang and co-workers (2012) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6. H. Zhao and co-workers (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7. Z.H. Zhang and co-workers (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8. Z.H. Zhang and co-workers (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9. C.S. Cheung and co-workers (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10. C.S. Cheung and co-workers (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11. M. Henke and co-workers (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12. P.M. Merritt and co-workers (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12.1. Test experimental setup and fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12.2. Emissions testing and analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12.3. Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.13. Overview of researchers’ works since 2004 to 1983 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1. Regulated emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2. Unregulated emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction The need for air quality improvements and the current cost of crude oil demands alternative fuels for automobiles/IC engines. The past and the present day civilization are closely interwoven with energy and in future, our existence will be even more dependent upon it [1]. Moreover, the sources of fossil fuel are dwindling day by day. According to an estimate, the fossil fuel reserves will continue until 41 years for oil, 63 years for natural gas and 218 years for coal [2–4]. The increasing industrialization and motorization of the world has led to dearth situation in the field of energy supply. Again the price of petroleum oil is becoming higher on daily basis. These pose a challenge to availability of fossil fuel. At these circumstances, demand of alternative biofuels is increasing as a substitute of fossil fuel in transportation sector for energy security issues. Among the biofuels such as biogas, bioalcohol and biodiesel, alcohol seems to be the most attractive and

1468 1468 1470 1470 1470 1470 1471 1471 1471 1471 1472 1472 1472 1473 1473 1473 1474 1475 1475 1475 1475 1476 1477 1477 1477 1477 1478 1480 1480 1480 1480 1480 1481 1482 1482 1482 1482 1483 1483 1483 1485 1485 1487 1487 1491 1491 1491 1491 1491

promising alternative fuels due to its storage facility, availability and handling. High pressure is required to use biogas for automobile. Again leakage from biogas may cause problem. Biodiesel from edible vegetable oil may cause the dearth situation to supply of food for population. The use of non-edible oil as biodiesel sources requires a large-scale cultivation that may cause decrease in food crops [5]. The greatest task today is to exploit the nonconventional energy resources for power generation. Alternative fuels are also called non-conventional fuels. Alternative fuels can be used with the present day petrol/diesel internal combustion engines with very little or no modification [1]. The development of alternative fuels to reduce automotive emissions and provide energy independence is becoming more important, especially following the increased public attention on energy security and environmental pollution [6]. Alcohols such as Ethanol and Methanol can be used as an alternative fuel in various gasoline engines [7,8]. In Brazil, Ethanol has been accepted as an alternative

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

fuel for the last 35 years [9,10]. In 1970, Methanol was used as a fuel during the oil crisis. In 1980 and 1990 the blending of Methanol with petrol was also used in different European countries. Both alcohols (Ethanol and Methanol) will be used as alternative fuels in pure form or in the form of blending with conventional fuels in future to reduce the demand for conventional fuels [11,12]. Alcohol fuels can also be used with diesel fuel in different duel fuel operation techniques. The most used methods are blending and fumigation. In blending method, alcohol fuels are mixed with diesel fuel before injecting inside the cylinder. To stabilize the miscibility of blending alcohol with diesel fuel extra additives are required. Hence there is a limitation on amount of alcohol which can be used for blending operation. Alcohol fumigation has been defined simply as the introduction of alcohol fuel into the intake air upstream of the manifold either by spraying, carbureting or injecting. This method of introduction has the advantage of providing a portion of the total fuel supply premixed with the intake air thus improving air utilization. This method requires minor modification of engine which is done by adding low pressure fuel injector, separate fuel tank, lines and controls [13,14] but allows a large percentage of alcohol fuels to be used in engine operation since no additives are required for stabilizing the miscibility of alcohol and diesel fuel [14,15]. As a result, the efficiency of engine will be better in fumigation mode [5]. This literature review study aims to investigate the definition and type of emissions (regulated and unregulated emissions) and alcohols and the influence of alcohol on emissions of IC engines. In the current literature review, two sections are provided. A brief detail of the effect of alcohols (methanol and ethanol) in blended and fumigation modes on regulated emissions in IC engines is presented at the first section. And the second section (which is main section of this work) is a comprehensive review part of the literatures related to the effect of methanol and ethanol in blended and fumigation modes on unregulated emissions in IC engines. In this literature review work, a wide type of IC engines, such as SI and CI engines and motorcycles are collected with different operation conditions. Different percentages of alcohol blend and fumigation are summarized to get informations about the effect of alcohols on regulated and unregulated emissions.

1443

processes are required to ensure the consistent production of diesel and gasoline from petroleum fuel [18]. Moreover in recent years concern about environmental pollution has been increased. Therefore, alcohol fuels are attracting attention worldwide as supplementary fuel [5]. The use of alcohol blended gasoline and neat fuel alcohols as substitutes for neat gasoline have become matters of interest in many countries. The International Energy Agency (IEA), established in 1974, follows the development, and data and other experience from various trials have been presented and discussed at symposia organized by the International Symposium on Alcohol Fuels (ISAF). The first ISAF-symposium was organized in Stockholm 1978 and since then a symposium has been organized every 2–4 years [19]. The number of models and types of alternative fuel vehicles produced by manufacturers has varied considerably over the last 22 years (Fig. 1). In 1991, there were a total of 19 models available that did not run on gasoline, 17 of which were diesel. In 2011 the number of models began to surge, rising to 175 models by 2013 and representing seven different fuel types. E85 (85% ethanol, 15% gasoline) flex-fuel vehicles accounted for the majority of new models available since 2010, although diesel and propane models contributed as well. But production of methanol vehicles was stopped in 1997. In addition, Fig. 2 represents the Alternative Fuel Vehicles in Use from 1995 to 2011. 2.1. Physicochemical properties of alcohol as a fuel Alcohol fuels such as ethanol and methanol are viable as alternative fuels for IC engines. The characteristics are:

2. Alcohol as a supplementary fuel in IC engines Alcohol is a form of renewable energy which can be produced from carbon based agriculture feed stocks, local grown crops and even waste products including waste paper, tree trimmings and grass [16]. Sugarcane residue is another renewable energy source of alcohol production [17]. In recent years, an increasing trend of alcohol fuel production from renewable sources has been found globally [5]. Alcohol is defined by the presence of a hydroxyl group (–OH) attached to one of the carbon atoms. The use of alcohol fuels in internal combustion engine is not new. These fuels have been used intermittently in internal combustion engine since their invention. The first commercial use of ethanol as fuel started when the automobile company Ford designed Henry Ford's Model T to use corn alcohol, called ethanol in 1908. Ethanol became established as an alternative fuel in 1970s due to oil crisis [13]. However, fossil fuel has been the predominant transportation fuel since the invention period of automotive engines due to the ease of operation for engine and availability of supply. But compared to alcohol fuels, fossil fuels have some disadvantages as an automotive fuel. Petroleum fuel has lower octane number and emits much more toxic emission than alcohol fuels. Due to having much more physical and chemical divers than alcohol, complex refining

Fig. 1. Number of vehicle models that run on fuels other than gasoline, 1991–2013 [20].

Fig. 2. Alternative fuel vehicles in use, 1995–2011 [20].

1444

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

 Alcohol has low viscosity than diesel fuel which makes the  



alcohol easily to be injected and atomized and mixed with air. Due to having high oxygen content, high stoichiometric air–fuel ratio, high hydrogen–carbon ratio and low sulfur content, alcohol emits less emission. Since alcohol has higher heat of vaporization, which results in cooling effect in the intake process and compression stroke. As a result the volumetric efficiency of the engine is increased and the required amount of the work input is reduced in the compression stroke. Alcohol has high laminar flame propagation speed, which may complete the combustion process earlier. This improves engine thermal efficiency [21,22].

Alcohol fuels such as ethanol and methanol have the same physical properties as that of petroleum fuels. The physical properties of alcohol fuels in comparison to gasoline and diesel fuels are given in Table 1.

 Be used (and already is on a wide scale) as an oxygenate in gasoline.

 Create new jobs in the country related to its production [19]. At least five major reasons for blending ethanol in gasoline are discussed, including the following advantages of using ethanol as an alternative fuel:

 Reduction of net carbon dioxide emissions, to mitigate global warming.

 The need to replace petroleum fuels with a renewable fuel.  The need (especially in the US) to improve the air quality in



non-attainment areas, i.e. areas of the country where air pollution levels persistently exceed the national ambient air quality standards. The need to reduce the dependence on imported fuels [19]. Disadvantages of ethanol as a fuel are the following:

 Ethanol has a lower heat of combustion (per mole, per unit of

2.2. Fundamental aspects of alcohol chemistry

volume, and per unit of mass) than petroleum.

2.2.1. Ethanol Ethanol, in particular, is a biomass based renewable fuel (bioethanol), which can be produced, relatively easily and with low cost, by alcoholic fermentation of sugar from vegetable materials, such as corn, sugar cane, sugar beets, barley, and from (non-food) agricultural residues such as straw, feedstock and waste woods [18,27,28]. The first generation bio-ethanol is made from high end stocks such as sugar cane, wheat, corn, etc., and is highly controversial, because of its consumption of food supplies. The second generation bio-ethanol is produced from low end stocks such as grass, wood chips, and agricultural wastes, therefore proving to be less controversial [29]. Ethanol also is known as absolute alcohol, alcohol, cologne spirit, drinking alcohol, ethane monoxide, ethylic alcohol, EtOH, ethyl alcohol, ethyl hydrate, ethyl hydroxide, ethylol, grain alcohol, hydroxyethane and methylcarbinol [30]. Ethanol is isomeric with dimethylether (DME) and both ethanol and DME can be expressed by the chemical formula C2H6O, C2H5OH or CH3CH2OH. Although that has the same physical formula, the thermodynamic behavior of ethanol differs significantly from that of DME on account of its stronger molecular association via hydrogen bonds [31]. As a fuel, ethanol has advantages and disadvantages over fuels such as gasoline and diesel fuel. The advantages of ethanol are that it can:

 Provide a viable alternative to reduce the greenhouse effect.  Be produced domestically, thereby reducing dependence on imported petroleum.

 Be easily mixed with gasoline. Table 1 Comparison of various propetrties of primary alcohol fuels with gasoline and diesel [23–26]. Fuel

Methanol

Ethanol

Gasoline

Diesel

Formula Molecular weight (g/mol) Density (g/cm3) Normal boiling point (°C) LHV (kJ/cm3) LHV (kJ/g) Exergy (MJ/1) Exergy (MJ/kg) Carbon content (wt%) Sulfur content (ppm)

CH3OH 32.04 0.792 64 15.82 19.99 17.8 22.36 37.5 0

CH3CH2OH 46.07 0.785 78 21.09 26.87 23.1 29.4 52.2 0

C7H16 100.2 0.737 38-204 32.05 43.47 32.84 47.46 85.5 200

C14H30 198.4 0.856 125–400 35.66 41.66 33.32 46.94 87 250

 Large amounts of arable land are required to produce the crops  

required to obtain ethanol, leading to problems such as soil erosion, deforestation, fertilizer run-off and salinity. Major environmental problems would arise out of the disposal of waste fermentation liquors. Typical current engines would require modification to use high concentrations of ethanol [32].

2.2.1.1. Usage of ethanol in blended and fumigation modes in IC engines. Ethanol is considered primarily a good spark ignition engine fuel, Because of its high octane number. Nonetheless, it has been considered also a suitable fuel for compression ignition engines, mainly in the form of blends with diesel fuel [18,27,33– 35], although investigations with pure ethanol (or methanol) have been conducted too [36,37]. For the latter case, cetane improvers and/or glow plugs were implemented combined with an increase in the engine compression ratio to facilitate ignition, particularly during cold starting. Another successful method for using alcohols in diesel engines is fumigation. In this technique, alcohol is atomized in the engine's intake air either by carburetion or injection. Diesel fuel is directly injected into the cylinder and the combined air–alcohol/diesel mixture is auto-ignited, with diesel fuel consumption being reduced by the energy of the alcohol in the intake air. This procedure, however, requires separate fuel systems for the diesel and ethanol fuel. Additionally, the amount of alcohol used is practically limited by the amount that can be vaporized into the intake air. As a result, this approach seems more feasible as an engine retrofit, where total energy substitution is not the primary objective [18,38]. However, unlike gasoline or diesel fuel, the vapors of ethanol above the liquid fuel in the fuel-tank are usually combustible at ambient temperatures, posing a risk of an explosion particularly during refueling [31]. The use of ethanol as substitute for gasoline gained considerable interest, mostly in the US (corn-based ethanol) and Brazil (sugar cane-based ethanol), following the global fuel crisis in the 1970s, although early applications originate from the 1930s [18,27]. The initial investigations into the use of ethanol in diesel engines, on the other hand, were initiated in South Africa in the 1970s, and continued in Germany and the US during the 1980s. Most of these works related to the use of in-farm equipment (tractors and combines) (e.g. [39]) and employed an ethanol/diesel fuel blend. The main benefit from the use of ethanol during (steady-state) diesel engine operation is the significant reduction of PM/smoke, due to the high oxygen content of the fuel blend [18,27,40–47]. Carbon monoxide emissions have been reported

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

lower too, but NOX as well as unburned HC may increase. At the same time, the specific fuel consumption has been reported usually higher owing to the alcohol's lower calorific value, but at a lower percentage compared to the decrease of the calorific value, hence the brake thermal efficiency is (usually) slightly higher [18]. Fig. 3 shows the atoms of ethanol in spatial arrangements. And ethanol production way is shown in Fig. 4. 2.2.1.2. Impact of ethanol on the physicochemical properties of gasoline. In the US Renewable Fuels Association (RFA) paper the impact of adding ethanol to the base fuel on the physicochemical properties of the fuel was discussed [49]. The properties considered are fuel volatility, vapor pressure, distillation properties, calculated drivability index, and vapor lock protection index in six classes (according to ASTM D 4814), oxygen content, water tolerance and gasoline additives. 2.2.1.2.1. Fuel volatility. Adding ethanol to gasoline will increase the volatility, decrease the 50% distillation point (T50), and affect both the drivability index and vapor lock protection [19]. 2.2.1.2.2. Vapor pressure. This is a measure of “front end” volatility, and a fuel with extremely high vapor pressure may cause problems with hot start ability, hot drivability and vapor lock [19]. 2.2.1.2.3. Distillation properties. Ethanol in gasoline will reduce the T50 value of the fuel, which may cause problems with older vehicles in warm weather. It has been shown that later models of fuel injected vehicles are less sensitive to a reduction in T50 than older cars [19]. 2.2.1.2.4. Drivability index. The drivability index is based on the relationship between the distillation temperature of the fuel and the cold start and warming up parameters of the vehicle. The following formula can be used to calculate the drivability index (DI): DI¼ 1.5T10 þ3.0T50 þ1.0T90 [19]. 2.2.1.2.5. Vapor lock protection index. ASTM D 4814 defines six classes of vapor lock production, as shown in Table 2. 2.2.1.2.6. Oxygen content. The standard for the oxygenate content in gasoline is set on a weight basis, as can be seen in Table 3. Since there are differences in the density of different grades of gasoline compared to the density of ethanol the final content of

1445

oxygen will vary if the blending volume is fixed to a certain volume [19]. 2.2.1.2.7. Water tolerance. It is well known that ethanol has affinity to water, so appropriate measures must be taken when blending ethanol with gasoline and during the distribution of ethanol–gasoline blends. According to the RFA the water tolerance of blended fuels is temperature dependent, i.e. the tolerance is lower at low temperatures. A 10% ethanol blend in gasoline will tolerate approximately 0.5% water (v/v) at temperatures of 15.5 °C or more, while the water tolerance is 0.3% (v/v) water at approximately
12 °C [49]. 2.2.1.2.8. Gasoline additives. Various additives may be used in gasoline, such as detergent deposit additives. For ethanol-blended gasoline the RFA recommends that ethanol producing member companies should "treat their ethanol with a corrosion inhibitor to ensure that any final blend is properly treated for corrosion protection”. The RFA has established recommendations for blending ethanol in gasoline, for storage tanks, for distribution, and at customer delivery points, for protecting pumps and meters. Many of these recommendations are certainly known by suppliers of ethanol blended fuels. However one of the recommendations is of great importance for those filling cars with ethanol blended gasoline, namely that: “When first converting to an ethanol program it is advisable to recalibrate meters after 10–14 days to ensure that the change of product has not caused any meters to over dispense" [49]. The effects of adding ethanol to gasoline on fuel properties have been discussed by Chandra Prakash in a report prepared for Environment Canada [51]. It was noted that inter alia, the advantage of using ethanol as an enhancer of the octane number of the blended fuel. As an example the author refers to a comparison (summarized in Table 4) of ethanol blended gasoline with neat gasoline. The author's essential message concerning the octane number was that the high octane rate of ethanol increased the value of the blended fuel. The author also pointed out that the higher octane number of the blended fuel conferred advantages in terms of fuel efficiency for later models of vehicles since they were commonly equipped with knock sensors, which retarded the ignition timing

Table 2 ASTM D 4814 vapor lock protection class requirements [50]. Vapor lock protection class

Fig. 3. Atoms of ethanol in spatial arrangement [30].

1 2 3 4 5 6

Vapor/Liquid (V/L)a,b Test temperature (°C)

V/L, max

60 56 51 47 41 35

20 20 20 20 20 20

a

At 101.3 kPa pressure (760 mm Hg). The mercury confining fluid procedure of test Method D 2533 shall be used for gasoline–oxygenate blends. Test Method D 5188 may be used for all fuels. The procedure for estimating temperature–V/L may only be used for gasoline (ASTM D 4814c). b

Table 3 Ethanol content and oxygenate content in fuels [49].

Fig. 4. Ethanol production way [48].

Fuel ethanol content (vol%)

Fuel oxygen content (wt%)

5.7 7.7 10

2.0 2.7 3.5

1446

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

in the event of knocking. In such cases the fuel would be more efficiently matched to the engine. The fact that ethanol had a lower heating value than gasoline may affect the performance of the vehicle, since the presence of an alcohol in gasoline would lean out the fuel, resulting in some loss of engine power. According to Prakash's work, this was somewhat offset by the fact that adding ethanol to gasoline results in a higher volume of combustion gases, which increased the pressure in the cylinder and thus increases the power efficiency by 1–2%.

As a definitive conclusion from Table 5, it may be suggested that methanol can be used as a partial substitute of diesel such that its advantages can be well exploited and shortcomings to be minimized. This is possible by operating diesel engines with dual fuel mode (blend or fumigation) with methanol and diesel. In energy deficit countries, Methanol can provide a sustainable solution against petroleum crisis due to the following reasons.

 Methanol can be manufactured from a variety of carbon-based feedstock such as natural gas, coal, and biomass (e.g., wood).

2.2.2. Methanol Methanol, also known as Carbinol, Columbian spirits, Hydroxymethane, Methyl alcohol, Methyl hydrate, Methyl hydroxide, Methylic alcohol, Methylol, Pyroligneous spirit, Wood alcohol, Wood naphtha and Wood spirit, is a chemical with the formula CH3OH (often abbreviated MeOH). It is the lowest alcohol with just one carbon atom, four hydrogen atoms and one oxygen atom. Fig. 5 shows the atoms of methanol in spatial arrangements. Methanol is an oxygenated fuel. It provides a clean combustion with negligible carbon footprints. In order to envisage methanol as a supplementary diesel engine fuel, it is essential that the physicochemical properties of the fuel is to be determined and then analyzed [52]. Methanol is usually synthesized from natural gas; as for hydrogen production, natural gas is ‘reformed’ to produce syngas and the syngas catalytically converted into methanol. This process has been in existence for over 40 years [35]. Methanol production way is shown in Fig. 6. Producing bio-methanol from biomass requires gasification (Fig. 7), cleaning of the gas and adjusting the H2/CO/CO2 balance to achieve a stoichiometric syngas. As the resulting syngas is CO2 rich there is an opportunity for sequestration. Bio-methanol can be produced using existing synthesis processes in large volumes. The only technical limitation has been producing large volumes of high quality syngas from biomass – now being resolved using advanced gasification technologies such as CHOREN's Carbo-V process [53].

 Use of methanol would diversify country's fuel supply and reduce its dependence on imported petroleum.

 Methanol is much less flammable than gasoline and results in less severe fires when it does ignite. So for fire safety purpose it is better than petroleum. Methanol has a higher laminar flame propagation speed, which may make combustion process finish earlier and thus may improve engine thermal efficiency [55]. Methanol is a high-octane fuel that offers excellent acceleration and vehicle power. Though the latent heat of methanol is higher, measures are not necessary for the mixture preparation due to lower fraction, while it may increase engine volumetric efficiency and thus increase engine power [56]. With economies of scale, methanol could be produced, distributed, and sold to consumers at prices competitive with petroleum.

 



Fig. 6. Methanol production way [48].

2.2.2.1. Usage of methanol in blended and fumigation modes in IC engines. Methanol has some advantage which causes to use it as a supplementary fuel in blend or fumigation modes for IC engines. Low cetane number, extremely low calorific value, and lower flash point are its disadvantages for direct diesel engine application. Table 5 provides a comparative assessment of methanol as a diesel engine fuel [54]. Table 4 Ethanol and gasoline octane numbers [51]. Property

Ethanol

Gasoline

RON MON (RON–MON)/2 Blending RON Blending MON

102–130 89–96 96–112 112–120 95–106

90–100 80–92 85–96 90–100 80–92

Fig. 7. Bio-methanol synthesis from biomass [53].

Table 5 Comparative study of methanol as a diesel engine fuel [54]. No. Methanol advantages

Methanol shortcomings

1 2

Longer ignition delay More corrosive

3 4 5 Fig. 5. Atoms of methanol in spatial arrangement [52].

High stoichiometric fuel air ratio High oxygen content, high hydrogen to carbon ratio and low sulfur content High latent heat of vaporization Reduced soot and smoke Higher cooling, hence less compression work

Lower energy content Lower flash point Poor combustion characteristics

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Due to high octane rating and similarities with gasoline, methanol has always considered as a good SI engine fuel. But bulk of the transport fuel consumed worldwide is diesel. Above all the major contribution to pollution also comes from diesel engines. Therefore, substitution of diesel by potential fuels like methanol by any method has more impact on economy and environment than substitution of gasoline by the same fuel [52]. 2.2.2.2. Impact of methanol on the physicochemical properties of gasoline. Adding methanol to gasoline causes changes in both the physical and chemical properties, primarily an increase in vapor pressure and changed distillation and materials compatibility characteristics. These changes in physical and chemical properties can have adverse effects on vehicle operation and emissions [57]. These changes and identifies some ways the changes can be managed as follows. 2.2.2.2.1. Vapor pressure. While the Reid vapor pressure (RVP) of methanol is only 4.6 psi (32 kPa), compared to gasoline that is typically in the range of 7–9 psi (48–63 kPa), adding methanol to gasoline causes an increase in vapor pressure. This is because methanol combines with certain low molecular weight hydrocarbons to form azeotropes. Azeotropes have lower boiling points than the hydrocarbons from which they are made, resulting in an increase in vapor generation at lower temperatures. Fig. 8 illustrates this phenomenon which has been documented widely by several researchers [58,59]. Fig. 8 shows that the effect of methanol on gasoline vapor pressure peaks with addition of around 10% methanol by volume, and decreases with larger additions, decreasing in an almost linear fashion to 4.6 psi at 100% methanol. (However, the increase in vapor pressure varies slightly with each blend of gasoline.) What is particularly significant when adding methanol to gasoline is the very rapid rise in RVP—the vast majority of the increase occurs by the time 2–3% methanol is added. This large increase in RVP creates very large increases in vapor generated, which often overwhelm the fuel evaporative system and result in significantly increased evaporative emissions. Co-solvents can moderate the increase in vapor pressure somewhat as illustrated in Fig. 8 for a 50/50 blend of methanol and TBA, but the most effective remedy is to decrease the RVP of the base gasoline. When used with co-solvents, the RVP peak occurs at around 5% alcohol content.

Fig. 8. The effect of alcohol addition to gasoline RVP [59].

1447

Fig. 9 shows the effect methanol and other alcohols have on the distillation curve of gasoline when added at the 15 wt% level. Methanol (labeled Cl in Fig. 9) shows the largest distillation curve distortion which is caused by the methanol and its azeotropes boiling off first. After about 60% of distilled, almost all the methanol is vaporized and the distillation curve reverts back to be nearly the same as for straight gasoline. 2.2.2.2.2. Water tolerance. While methanol is soluble in gasoline, the presence of water may cause phase separation (water and methanol separate out of solution). Whether phase separation occurs depends on the amount of water and the temperature— high water content and low temperatures favor phase separation. Methanol is the worst alcohol in regard to phase separation, which is one of the reasons that higher molecular weight alcohols have been frequently recommended as co-solvents for methanol/gasoline blends. Co-solvents ameliorate phase separation, vapor pressure increase, and materials compatibility problems. The EPA has required co-solvents for all methanol blend waivers for these three reasons. For high methanol content fuels such as M85, phase separation is not a problem because of the large capacity of methanol to absorb water [57]. Fig. 10 shows the water tolerance of a gasoline with various concentrations of methanol. This figure vividly illustrates how methanol addition quickly causes the temperature at which phase separation occurs to rise. For example, 10 wt% methanol will separate when the blend is cooled to a temperature of only 15°F (
9 °C). At 15 wt% methanol the phase separation temperature rises to just below freezing. Co-solvents can have a dramatic effect on the water tolerance of gasoline blended with methanol. Fig. 11 shows the impact that adding 5 wt% alcohol co-solvents can have on the water tolerance of a 10 wt% blend of methanol in gasoline. The higher alcohols of Fig. 11 significantly improve the water tolerance of methanol blends. 2.2.2.2.3. Materials compatibility. Automotive fuel systems contain a wide range of elastomeric and metallic components. The elastomers are used primarily as seals and fuel lines but vehicle manufacturers have recently been moving to fuel lines that are nonmetallic all the way from the fuel tank to the engine fuel system, which greatly increases the amount of wetted area between the

Fig. 9. The effect of alcohol addition to gasoline distillation [58].

1448

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Fig. 12. Elastomer swell from exposure to gasoline, methanol, and a 10% methanol blend [59].

Fig. 10. The water tolerance of methanol added to gasoline [58].

Fig. 11. The impact of co-solvents on the water tolerance of a 10 wt% blend of methanol in gasoline [58].

elastomers and the fuel. Many fuel tanks are now non-metallic as well for reasons of cost and ability to be molded into complex shapes that maximize volume in tight vehicle confines [57].

Elastomers must not crack, leak, or become permeable to fuel; if they do, vehicle safety is impaired and/or evaporative emissions increases will occur. No elastomer is completely unaffected by exposure to fuel, with changes occurring in volume (swell), tensile strength, and elongation. The addition of methanol to gasoline causes changes in elastomers that are difficult to predict. Fig. 12 illustrates testing done on various generic elastomers used in fuel systems (measuring swell) using two gasoline, neat ethanol, and a blend of the base gasoline and 10% methanol [59]. In general, neat methanol caused less swelling of the elastomers than the blend of 10% methanol in gasoline, and in most cases, the 50% aromatic gasoline caused more swelling than 10% methanol. Only the fluorocarbon showed more swelling in methanol and the 10% blend than in either of the gasoline tested [57]. Figs. 13 and 14 show additional test data complementary to the results in Fig. 12 for polyester urethane and fluorocarbon over the entire range of methanol blends from 0% to 100% [60]. These data show that elastomers change continuously with percent methanol content, with the greatest change often occurring with an intermediate blend. A field trial of 4% and 15% methanol in gasoline in Norway reported swelling of some fuel lines, though the amount was not quantified [61]. In a similar field trial of M15 in New Zealand, problems with fuel lines were observed along with other fuel system elastomers including carburetor needle valve seats, fuel tank level floats, and fuel pump diaphragms [62]. The problems reported in the New Zealand fleet test were judged to be relatively minor and were easily corrected by replacement with new parts. Without a control fleet, it is not known whether these problems represented a significant change or not [57]. These data suggest that the impact of methanol on elastomer materials is relatively benign compared to high aromatic gasoline. However, these tests were done using new elastomers and relatively pure fuels. As elastomers age in service, they are less amenable to change. There are several instances of field problems caused by changes in fuel properties. For example, the change to ultra-low sulfur diesel fuel caused numerous fuel system leaks because the elastomers were adversely affected by a relatively small change in fuel properties. New versions of the same elastomers worked, illustrating the impact aging can have on fuel system elastomers. Other confounding factors include the shape of the elastomer and whether it is attached to a metal that might be attacked by methanol. Complex-shaped elastomers may react differently than the uniform elastomer shapes used for testing. Methanol fuels of all types can be extremely aggressive toward magnesium and, if they contain dissolved or separated water, toward aluminum, also [63], Steel and other ferrous metals are usually only slightly affected unless the blend has a separated water phase, in which case some pitting may occur. Additives have been found to be effective in reducing the corrosive effects of methanol in gasoline (blends of up to 10%) on

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Fig. 13. Polyester urethane compatibility with ethanol and methanol blends (Gasoline A from Fig. 12) [60].

copper, cast iron, steel, and aluminum [64]. Corrosion inside 4-stroke engines can be controlled through the use of properly formulated engine oils [65]. 2.2.2.2.4. Oxygen content. Gasoline and diesel fuels produced from crude oil are composed entirely of compounds that are composed almost entirely of carbon and hydrogen with very small amounts of nitrogen and sulfur. In contrast, methanol is 50% oxygen with the remainder being carbon and hydrogen. As a result, methanol needs less air for complete combustion since the oxygen in its composition displaces the need for oxygen in the air. The stoichiometric air/fuel ratio for methanol (weight basis) is 6.45 (mass air to mass methanol) compared to about 14.7 for gasoline. Fig. 15 shows the impact this has on blends of gasoline and methanol. As methanol is added to gasoline, the oxygen content of the blend goes up, but, since the oxygen does not contribute to heating value, the volume of fuel needed to generate the same power increases. (This discussion assumes that the efficiency of the engine does not change with the amount of methanol, which is reasonable for fixed compression ratio engines.) Thus, a blend of 10% methanol in gasoline requires approximately 105% of the volume of straight gasoline to make the same amount of power. If an engine were capable of operating on 100% methanol, it would require twice as much fuel volume compared to an engine running on straight gasoline [57] Fig. 16. The preceding discussion assumes the engine is designed for gasoline but is using methanol blends with gasoline. Engines optimized for use of methanol blends where methanol is the predominate component, such as 85% methanol (M85), can be made more efficient through use of higher compression ratios and other

1449

Fig. 14. Fluorocarbon compatibility with ethanol and methanol blends (Gasoline A from Fig. 12) [60].

engine adjustments optimized to methanol. In addition, an engine optimized for high methanol blends can have higher specific power output, creating the opportunity to reduce engine displacement for a given application. With both an engine optimized for methanol and reduced engine displacement, significant increases in energy efficiency are possible relative to gasoline engines [57]. 2.2.2.2.5. Octane value. Methanol has good octane properties compared to gasoline. With a research octane value of 108.6 and a modified motor octane value of 88.6, methanol has sufficient octane to allow engines optimized for methanol to have high compression ratios with the attendant benefits of improved power and efficiency. When used in blends, the high octane value of methanol can be used to reduce the refining severity of the associated gasoline blend stock, allowing increases in refinery output and efficiency [57]. 2.3. Differences of physicochemical characteristics of methanol with ethanol In the complete report [66], Chevron discussed the implications of the observation that “Methanol is not Ethanol” in that they had different physicochemical characteristics. According to Chevron:

 Blends of gasoline with methanol are more corrosive towards 

metals and cause more rapid deterioration of elastomers in the fuel system. Methanol–gasoline blends are not authorized by many manuals for vehicle owners.

1450

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

oxygenated gasoline did not cause rusting or corrosion, but water from the phase separation of gasoline oxygenated with ethanol will, given time”. 2.4. Overview of fossil and alcohol fuels Different fossil and alcohol fuels currently existing on the market as well as fuels that are under development are presented in Table 6. Table 7 shows suitable fuels for different vehicle sizes, driving patterns and combustion types. 2.5. Alcohol productions and economics in the world

Fig. 15. Oxygen content and fuel volume ratio for gasoline/methanol blends [57].

2.5.1. Ethanol productions and economics in the world The U.S. is the world's largest fuel ethanol producer, accounting for nearly 60% of global output in 2014. Brazil, which produced roughly 6.2 billion gallons, was responsible for about 25% of world production, while the European Union followed with 6%. China and Canada were other leading producers [71]. Fig. 17, represents the fuel ethanol production in different countries. There are many benefits to the economy when building, producing and selling ethanol in the word. For instance, the production of 14.3 billion gallons of ethanol in the U.S. in 2014 had substantial economic impacts, including:

    

Fig. 16. 2014 Global fuel ethanol production in different countries (country, million gallons, share of global production) [71].

 The vapor pressure of a methanol–gasoline blend is significantly higher than that of a corresponding ethanol–gasoline blend.

 Methanol is toxic.  

 





In addition, the following performance-related issues have been highlighted by Chevron: Compared to neat gasoline, ethanol/gasoline blends need more heat to evaporate, which can reduce drivability. Blending ethanol in conventional gasoline, if it is not adjusted for such blending may result in a fuel with too high volatility (in this context the alcohol's previously mentioned effect on the VL ¼20 temperature is relevant). Since ethanol increases the volatility of the fuel, adding it has not been a viable option for summer reformulated gasoline. Ethanol blended gasoline is not to be mixed with neat gasoline that has not been adjusted for such blending, since the resulting commingling will result in the RVP of the fuel in the tank exceeding standard limits. Conventional gasoline can dissolve up to 150 ppm water at 21 °C, depending on its aromatics content. An ethanol–gasoline blend with 10% ethanol can dissolve up to 6000–7000 ppm water at 21 °C. Phase separation may occur if ethanol blended gasoline is transported in pipelines. Some metal components in the engine fuel system will rust or corrode if water or acidic compounds are present in the fuel system. According to Chevron “additional water dissolved in

83,949 direct jobs 295,265 indirect and induced jobs $53 billion contribution to gross domestic product $27 billion in household income $10 billion in tax revenues [71].

2.5.2. Methanol productions and economics in the world In 2012, the world methanol capacity utilization rate was just over 70%. The global methanol supply registered stable positive growth from 2010 to 2012. In 2012, it stood at more than 62.9 million tons. China was an unrivaled methanol manufacturer in 2012, but the country used its production capacities only at approximately 60% of their total potential. China is the largest country of capacity (Fig. 17) and also demand for methanol. Currently, the major methanol producers are based in the developing regions, like the Middle East and Asia-Pacific. Asia-Pacific accounted for over half of the global methanol supply volume in 2012. Methanol is used to produce acetic acid, formaldehyde, and a number of other chemical intermediaries that are utilized to make countless products throughout the global economy—and by volume, methanol is one of the top 5 chemical commodities shipped around the world each year. The global methanol industry generates $36 billion in economic activity each year, while creating over 100,000 jobs around the globe [73]. The development of a methanol economy in China which is the largest methanol producer and user has profound economic and environmental implications. Coal-based methanol production could provide China with a domestic alternative to imported oil and reduce conventional automotive emissions [74]. In addition, the U.S. economic impacts of methanol are the following:

 Domestic methanol plants and production of its derivative



products (methanol fuel cells, building materials, plastics) already provide thousands of valuable high-skilled jobs to the U. S. economy. Renewable methanol fuel and derivative fuels such as biodiesel and dimethyl ether (DME) can help efficiently and economically achieve the U.S. Renewable Fuel Standard.

Table 6 Overview of fossil and alcohol fuels [67].

Ethanol

Highlighted emission components

Is conversion of the engine required in order to use this fuel?

Current limitations for increased usage

Outlook for future use: Limited amount of raw material

Current use

Increased demand from emerging markets.

Possibly less use in the future due to European legislation (EU Renewable Energy Directive [68]) to increase use of renewable fuels; Continued usage as blending component in biofuels. Possibly less use in the future due to European legislation (EU Renewable Energy Directive [68]) to increase use of renewable fuels; Continued usage as blending component in biofuels. Questions for Euro VI usage.

All over the world in SI applications; Potential to blend with different biofuels.

Fossil petrol

Crude oil

Fossil diesel

Crude oil

Aromats, PAH, Mutagenic, NOX, particles

ED95

E.g. crops/biomass with sugar and/or starch content

Ultrafine particles, aldehydes (mainly acetaldehyde)

Yes. Minor adjustments

Vehicle availability (ED95 only for dedicated vehicles).

E85/E100

E.g. crops/biomass with sugar and/or starch content E.g. crops/biomass with sugar and/or starch content

Aldehydes (mainly acetaldehyde)

Yes. Minor adjustments

Vehicle availability.

Low blends in fossil petrol

Methanol

Raw material(s)

M85/M100

Methane (natural gas, biogas) steam reformed coal, woody biomass

Increased demand from emerging markets.

Blending of 410% require vehicle None for 0–10% [70] mixture in petrol; Compatible if modifications. complying with blending requirements in EN228. Highly toxic;v Corrosive properties; Toxic when handling! Insufficient experience Production capacity for biomethaAldehydes (mainly nol; Vehicle availability; up to 3% formaldehyde) methanol is allowed according to current EU standard (EN228).

All over the world in Cl applications; Potential to blend with different biofuels.

Norway, Sweden, Finland, France, Holland, Poland, Spain, South Africa, Brazil, Thailand, Australia Current EU ILUC proposal suggests max EU, USA, China and Brazil 5% of 1st generation ethanol. (E100) [69] EU, USA, South America, Southeast Asia, Current EU ILUC proposal suggests max 5% of 1st gen- China eration ethanol. Major engine modifications required; Investment in fueling equipment and infrastructure; Safety and health concerns.

Limited use (mainly in China), blended in petrol and diesel; Some provinces in China use M15 and M85 (blends with petrol).

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Renewable fuel Fuel, commercially available

1451

1452

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Table 7 Overview of fossil and alcohol fuels suitable for different vehicles [67]. Fuel

Fossil diesel Fossil petrol Ethanol, high blend Ethanol, low blend in fossil petrol ED95 (95% ethanol and 5% ignition enhancers) Methanol, low blend in fossil petrol

Light vehicles, Cl engines

Light vehicles, SI engines

Heavy vehicles, haulage

Heavy vehicles, urban

X – – –

– X X X

X – – –

X – – –

–

–

X

X

–

X

–

–

Fig. 17. Global methanol production by country, 2012 [72].

 In 2010, the U.S. consumed 5.3 million tons estimated to be a



$1.4 billion dollar industry. Extrapolated with the Commerce Department's'ripple effect' multiplier for energy industries, the total economic impact in the U.S. is $3.5 billion dollars annually at current consumption rates. Expanded use of methanol as a clean-burning fuel source could provide tens of thousands more jobs at various skill levels and billions of dollars additionally in the clean energy economy [75].

3. Emissions 3.1. Regulated exhaust emissions The methods used to determine regulated pollutants have been developed for application to conventional fossil based gasoline and diesel fuels. These methods are: chemiluminescense detection for NOX, nondispersive infrared detection (NDIR) for CO, gravimetric analysis for particulates and flame ionization detection (FID) for HC. The chemical constituents of HC are, by definition, hydrocarbons which consist solely of carbon and hydrogen atoms. However, the chemical compounds emitted include compounds other than pure hydrocarbons in relative abundances that vary depending on the fuel used, so the “HC” signal from the FID tends to be underestimated. This is because the hydrocarbons and partially oxygenated compounds have different response factors, as widely reported in the scientific literature (Table 8). Consequently, to make a valid comparison of HC emissions from gasoline and ethanol blended gasoline as fuels the comparison must be made compound by compound to avoid over- or under-estimations. This requires the development of a method enabling the separate detection of hydrocarbons and alcohols (at least) in exhaust emissions [19].

Table 8 Sensitivity of the flame ionization detector towards selected compounds relative to that of the hydrocarbon n-heptane (C7H16), which is set to 1.00 [76]. Hydrocarbons Methane Ethane

0.97 0.97

Alcohols

Organic acids

Methanol Ethanol

0.23 0.46

Formic acid Acetic acid

0.01 0.24

Emission measurements must be carried out as part of the type approval of the vehicle according to relevant legislation, for example the European regulations (current EU Directive 70/220 EEG with amendments). There is also a need for emission testing to generate emission factors for use in emission inventories and air quality studies. Characterization of emissions from vehicles is also essential for research purposes. Emission tests are commonly carried out according to standard procedures to enable data generated at different laboratories or during different projects to be compared. There may also be a need to generate emission factors for local traffic situations, in which case specific driving patterns (driving cycles) may have to be followed when testing the vehicles, depending on the regulations in force [19]. In both the US and Europe, a plethora of new diesel engine emission control standards has led to an ever changing description of DPM and its attendant gases and vapors [77]. Since 1992, there has been a staged introduction of new regulations affecting the emission of nitrogen oxides, hydrocarbons, and PM in on-road diesel-powered vehicles. The values presented in Table 9 show that the allowable emission of DPM has declined steadily in both passenger cars and commercial vehicles. The emission of hydrocarbons and nitrogen dioxide in diesel exhaust from passenger and commercial vehicles was also projected to decline by more than 5fold for the 12-year period beginning in 1992. The United States Environmental Protection Agency (USEPA) has developed a similar set of emission limits that have been promulgated in two separate phases lasting 5 years each. A third tier of regulations was initiated in 2010 and is scheduled to end in 2016. The promulgation of these increasingly stringent regulations has required engine manufacturers to make dramatic changes in the combustion characteristics of new engines and introduce new pollution control measures, such as fuel reformulation, diesel particulate filters (DPFs), and oxidation catalysts [78]. Since these technologies will continue to be modified and improved to meet future restrictions on DPM and hydrocarbon emissions, the diesel emissions of today will undergo further change with the types and quantities of each pollutant shifting with time [79]. Emissions that are regulated by law [80] are carbon monoxide (CO), unburned fuel hydrocarbons (HC), nitrogen oxides (NOX) and, for diesel cars, particles [19]. And today in Europe, the U.S. and Japan (the 3 major regions) there are currently regulated limits for: Particulate Matter (PM), Carbon Monoxide (CO), Nitrogen Oxides (NOX) and Hydrocarbons (HC). 3.1.1. Particulate matter (PM) It can be referred to as diesel particulate matter (DPM) or total particulate matter (TPM). Diesel PM is a mixture of carbonaceous soot, as well as other solid and liquid material [81]. 3.1.2. Carbon monoxide (CO) Carbon monoxide (CO) is a poisonous, colorless, odorless, and tasteless gas. CO is a common industrial hazard resulting from the incomplete burning of natural gas and any other material containing carbon such as gasoline, kerosene, oil, propane, coal, or wood. Forges, blast furnaces and coke ovens produce CO, but one

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

1453

Table 9 European emission standards for nitrogen oxides, hydrocarbons, and PM in diesel exhaust [79]. Tier

Euro Euro Euro Euro Euro Euro

Date

I II III IV V VI

July 1992 Jan. 1996 Jan. 2000 Jan. 2005 Sep. 2009 Sep. 2014

Passenger cars (g/km)

Commercial vehicles o 1760 g (g/km)

Commercial vehicles 41760 g (g/km)

NOX

HCþ NOX

DPM

NOX

HCþ NOX

DPM

NOX

HC þNOX

DPM

– – 0.50 0.25 0.180 0.080

0.97 0.7 0.56 0.30 0.230 0.170

0.14 0.08 0.05 0.025 0.005 0.005

– – 0.50 0.25 0.180 0.080

0.97 0.7 0.56 0.30 0.230 0.170

0.14 0.08 0.05 0.025 0.005 0.005

– – 0.78 0.39 0.280 0.125

1.7 1.2 0.86 0.46 0.350 0.215

0.25 0.17 0.10 0.06 0.005 0.005

of the most common sources of exposure in the workplace is the internal combustion engine [82]. 3.1.3. Nitrogen oxides (NOX) Nitrogen oxides (NO and NO2) are formed by the oxidation of nitrogen from the air in the combustion process. An important parameter for the formation of nitrogen oxides is the combustion temperature i.e. increased combustion temperature results in increased nitrogen oxide emissions. It should be noted that nitrogen oxides (NOX) are regulated pollutants that are determined jointly, as the sum of NO and NO2 contents rather than as individual components [19]. 3.1.4. Hydrocarbons (HC) From a strictly chemical perspective, hydrocarbons consist solely of the elements carbon and hydrogen. When using gasoline as fuel in an Otto engine, the unburned fuel hydrocarbons (HC) in the exhaust consist mainly of unburned gasoline which itself largely consists of hydrocarbons. However, when using gasoline/ ethanol blends as fuel the un-combusted fuel constituents include both unburned gasoline (which consists mainly of hydrocarbons as noted) and un-combusted ethanol. Thus, the HC emissions measured in the diluted exhaust consist of both hydrocarbons and ethanol (alcohol). From a legal perspective, HC emissions are regulated by law, but not ethanol emissions. This means that reported HC emissions from vehicles fueled with alcohol/gasoline blends are overestimated, due to the contribution of the alcohol contents in the exhaust emitted from the vehicle, and the larger the alcohol contents present in the exhaust, the greater the error in estimated HC emissions [19]. Fig. 18 details the trend which European emissions regulations have followed during the last 18 years and how they are projected to be for Euro 6 in 2014. It should also be considered that since Euro 5 there is an additional PM requirement, for a PM total number limit at 6*1011 km
1 [81]. 3.2. Unregulated exhaust emissions There are several additional unregulated pollutants that have been found in Cl engine exhaust, which many of them are at much lower concentration levels than the regulated emissions. Indeed, some represent a part of the complex PM emission whereas others are gas phase species. The US EPA has estimated that more than 20,000 individual chemical compounds are emitted from diesel fueled vehicles [83], approximately 500 of which have been positively/tentatively identified in the scientific literature. This means that more than 97% of the estimated compounds emitted from diesel vehicles are unknown (as are, therefore, their health effects) [19]. However, a selection of unregulated exhaust constituents is considered below that are considered to be important and to have potential health effects on animals and humans, and thus should be monitored and reduced in exhaust emissions from automotive sources. The list of such compounds which is expected

Fig. 18. European emission standards for passenger cars [81].

to be updated and modified according to future findings is as follows. 3.2.1. Alcohols When alcohols are used as blending components in fuel, uncombusted alcohols from the fuel are emitted in the exhaust in various amounts. These un-combusted alcohols in the exhaust emissions should be measured since there is a risk that the “HC” signal from the FID will be overestimated, leading to estimates of HC emissions from alcohol blended gasoline fuels being higher than they really are [19]. 3.2.2. Alkenes Alkenes such as ethene, propene and 1,3-butadiene can be potentially metabolized by endogenous enzymes to reactive metabolites, which have the potential to initiate cancer. For instance, the compound 1,3-butadiene is metabolized to ethylene oxide in both animals and humans [84,85]. According to Schuetzle et al. [86] significant sources of 1,3butadiene are the olefins in the fuel. By blending gasoline with ethanol the “fuel olefin” content decreases, suggesting that emissions of alkenes are reduced when it is used rather than neat gasoline. However, this hypothesis needs to be experimentally confirmed [19]. 3.2.3. Alkyl nitrites Methyl and ethyl nitrite are mutagenic [87,88], hence they are potential carcinogens. Alkyl nitrites are formed from un-combusted alcohol reacting with nitrogen oxides (NOX) in exhaust plumes. From vehicles fueled with methanol/gasoline blends and methanol/ diesel blends methyl nitrite is formed [89]. Both methyl and ethyl

1454

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

nitrite are formed in exhaust plumes from vehicles fueled with ethanol–gasoline blends [90]. 3.2.4. Monoaromatics Monoaromatic compounds emitted from vehicles include benzene, toluene, ethyl benzene and xylene, which are often collectively called BTEX. According to the California Air Resources Board [91] benzene is a known human carcinogen and may cause leukemia through occupational exposure [92]. A source of BTEX emissions from vehicles is the BTEX content of the fuel used, emitted in the un-combusted fuel constituents. However, BTEX can also be pyrosynthesised in the combustion process from the fuel or lubricating oil constituents [19]. 3.2.5. Particulate emissions Participate emissions are measured on a weight basis i.e. through gravimetric determination using a dilution tunnel technique at a diluted exhaust temperature below 52 °C. Exposure to diesel exhausts clearly induces lung tumors in rats. These neoplasms may be caused by the particle fraction of the exhaust [93–95]. Due to the findings that TiC2 and carbon black particles, with no genotoxic compounds adsorbed on them (i.e. “clean” particles) can also give rise to lung cancers in rats [96–98] interest in particles per se has increased. Important particle parameters in general are their size, number, surface area and chemical composition. Studies by Heinrich et al. [99] indicated that particle size was a very important parameter. The Institute of Environmental Medicine (Karolinska Institute, Sweden) had published a report which concluded that it was not currently possible to tell if a nonspecific particle factor or a direct genotoxic effect of material adsorbed on the particles is responsible for causing lung cancer [95]. Therefore, the particles emitted should be chemically analyzed with respect to both their size and numbers [19]. 3.2.6. Peroxvacetyl nitrate (PAN) Peroxyacetyl nitrate is a peroxyacyl nitrate. It is a secondary pollutant present in photochemical smog. It is thermally unstable and decomposes into peroxyethanoyl radicals and nitrogen dioxide gas. It is a lachrymatory substance. Peroxyacetyl nitrate, or PAN, is an oxidant more stable than ozone. Hence, it is better capable of long-range transport than ozone. It serves as a carrier for oxides of nitrogen (NOX) into rural regions and causes ozone formation in the global troposphere. The formation of PAN on a secondary scale becomes an issue when ethanol is used as an automotive fuel. Fig. 19 shows the chemical structures of Peroxyacetyl nitrate. In a study by Gaffney et al. [100] field measurements taken in Albuquerque, New Mexico, were used to compare atmospheric levels of peroxyacetyl nitrate (PAN) associated with the use of different fuels. Levels were measured before and after introduction of a 10% ethanol gasoline fuel blend ( 499%) and the cited authors detected increased levels of PAN and aldehydes during the wintertime. A study [101] which was more valid during summertime conditions in Porto Alegre, Brazil, indicated that aromatics and alkenes have a major role, and acetaldehyde and ethanol minor roles, as precursors to PAN in urban air-in contrast to a report prepared by the Orbital Engine Company [102] for Environment Australia,

which stated that acetaldehyde is particularly important since it reacted with NOX, forming PAN in the atmospheric photochemical system. 3.2.7. Polycyclic aromatic hydrocarbons (PAHs) Polycyclic Aromatic Compounds (PACs) are a numerous group of mutagenic carcinogenic compounds, of which a subgroup (Polycyclic Aromatic Hydrocarbons or PAHs), consists of mutagenic carcinogenic hydrocarbons [93,94]. Each PAH has a relatively large number of hydrocarbons with two or more condensed aromatic rings. However, in Sweden are the PAHs phenanthrene, fluoranthene, pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(l,2,3-cd)pyrene, dibenz(a,h)anthracene, dibenzo(a,l)pyrene, methyl anthracenes/phenanthrenes, retene and benzo(ghi)perylene recommended by the Swedish Environmental Protection Agency (SEPA) for air monitoring programs in 1999, which published in 2002 [104]. Fig. 20 shows the priority listed PAHs. Some of compounds shown in Fig. 20 are considered as 'probable human carcinogen' (B2), while some are not listed as 'human carcinogens' (D) [105]. The toxicity of these PAH compound is highly dependent on their molecular structure. Two isomers of PAHs with different structure show quite different toxicity. Therefore EPA has divided these PAH compounds into different categories [106].

Naphthalene* C10H8

Fluorine (D) C13H10

Acenaphthene C12H10

Anthracene (D) C14Hl0 Phenanthrene (D) C14H10

Fluoranthene (D) C16H10

Pyrene (D) C16H10

Benzo[a]anthracene (B2) C18H12

Chrysene (B2) C18H12

Benzo[b]fluoranthene (B2) C2H12

Benzo[k] fluoranthene C20H12

Benzo[j]fluoranthe ne C20H12

Henzo[a]pyrene (B2) C20H12

Dibenz[a,h]anthrac ene (B2) C22H14 Fig. 19. Chemical structure of Peroxyacetyl nitrate (PAN) [103].

Acenaphthylene (D) C12H8

Benzo[ghi]perylene (D) C22H12

Henzo[e]pyrene C20H12

Indeno[1, 2,3c,d]pyrene (B2) C22H12

Fig. 20. Priority list PAHs [105]. *—Not included in priority list; D—not listed as to human carcinogens; B2—probable human carcinogen.

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

1455

Table 10 (continued ) Compound

Fig. 21. Carbonyl group, aldehyde and ketone [106]. Table 10 Emission factors for carbonyls in the gas and particle phases of diesel and gasoline exhaust [126]. Compound

Aliphatics Propanal Butanal Isobutanal Pentanal Hexanal Heptanal Octanol Nonanal Decanal Undecanal Dodecanal Tridecanal Tetradecanal

Aliphatic ketones 2-Butanone 3-Pentanone 2-Pentanone 2-Hexanoiie 2-Heptanone 2-Octanone 2-Nonanone

Unsaturated aliphatics Acrolein Methacrolein Methyl vinyl ketone Crotonaldehyde t-2-Methyl-2-butenal 3-Methyl-2-butenal t-2-Hexanal 4-Hexen-3-one 5-Hexen-2-one

Light-duty gasoline emission factor (lg/L)

Heavy-duty diesel emission factor (lg/L)

Gas phase

Particle phase

Gas phase

Particle phase

70 1900

87 27 1.7 7.6 3.6 13 1.2 8.1 2.3

160 8800

210 500 21 170 540 160 35 260 140 Det 59

770 420 18 35 390 110 18 56 17

54

Aromatic aldehydes Benzaldehyde o(& m)-Tolualdehyde p-Tolualdehyde t-Cinnamaldehyde 3,4,-Methyl-benzaldehyde 2-Ethyl-beiizaldehyde 4-Ethyl-benzaldehyde 1-Naphthaldehyde 2-Naphthaldehyde

98 34 28 350 140 180 740

220 3.9 2.4

5.3

4.3

0.4

22

6.3 11 110

140 38 310 41

2.5 0.5 7.5

2.1 1.5

210 29

0.5

83

1.2

0.3

14 4.9

0.1

27 89 41

16 34

140 4200

170 1400

3 3200 290

2.1 1200 110

660 210 180 36 100 130 500 230 380

130 1.9 2.8

Cyclic aliphatics 2-Methyl-2-cyclopentenone 0.7 3-Methyl-2-cyclopentenone 1.6 2-Cyclohexenone 2

Aliphatic dicarbonyls Giyoxal Methyl giyoxal 2,3-Butanedione 2,3(& 2,4)-Peixtaixedione 2,3-Hexanedione 2,5-Hexanedione

6 0.2

2100 7000 690 590 140 860 380 410 380 1600

21 550

Det

55 23

7.9 46 0.4 Det 32 4.1

9–7 11 26

9–5 4.3 4

19 14 9.3 10

37 3.6 5.7

Light-duty gasoline emission factor (lg/L)

Heavy-duty diesel emission factor (lg/L)

Gas phase

Gas phase

Particle phase

4-Biphenylcarboxaldehyde

Aromatic ketones Acetaphenone 1-Indanone 9-Fluorenone Benzophenone Periiiaphthenone Xanthone

Aromatic dicarbonyl 1,2-Acetylbenzene 1,3-Acetylbenzene 1,4-Acetylbenzene Naphthalic anhydride

Particle phase

100

4 5.7 2.9 1.7

1 7.9 2

1.2 0.3 0.7

230 75 190 88 38

1.8 24 20 43 5

49 130 28 130

In recent decades, it is reported that PAHs presents in the diesel particulates are one of the main factor, which adversely affect human health. PAHs include various kinds of poly-aromatic compounds, which manifest different toxic properties. EPA has listed 16 PAHs as carcinogenic, probable carcinogenic and possible carcinogenic and the molecular structure of these is shown in Fig. 20 [105]. 3.2.8. Nitro-PAHs and Oxy-PAHs Nitro-PAHs are emitted in the atmosphere by primary sources [107] or formed by gas phase PAHs reacting with hydroxyl (OH) radicals during the daytime and nitrate (NO3) radicals during the nighttime, in the presence of NOX [108–110]. Nitro-PAH isomer patterns resent in direct emissions are significantly different from those resulting from atmospheric reactions, reflecting thus their formation pathways. During incomplete combustion processes, 1nitropyrene (1-NP) and 3-nitrofluoranthene (3-NF), formed by electrophilic nitration, are the most abundant compounds found in diesel fuel particulate material [107]. Conversely, gas-phase reaction pathways involve OH radical attack at the sites of highest electron density, with subsequent NO2 addition followed by a loss of water [107]. The most abundant nitroarenes produced by this mechanism are 2-nitrofluoranthene (2-NF) and 2-nitropyrene (2NP) [107]. Equivalent to the OH reaction, the attack of the NO3 radical forms a fluoranthene–NO3 adduct, followed by the Ortho addition of NO2 and subsequent loss of HNO3 [107]. This reaction is notably selective, forming only 2-NF. In the atmosphere, the gas-phase reactions of PAHs with OH and NO3 radicals form 2-NF, which is the most abundant particle associated nitro-PAH [111,112]. Oxygenated PAH compounds (oxy-PAHs) such as aromatic ketones, aromatic aldheydes, quinones, and carboxylic acids have been identified in various environmental samples [113–115]. OxyPAHs are mainly emitted from combustion processes; however, they are also produced by heterogeneous reactions of particulate associated PAHs with ozone [107,113,116]. 3.2.9. Carbonyl compounds Diesel engines emit large number of different harmful compounds and many compounds are still unknown. The term carbonyl refers to the carbonyl functional group, which is a divalent group consisting of a carbon atom double-bonded to oxygen. Carbonyls are such compounds, which have significant presence in

1456

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

engine exhaust. Most studies have measured carbonyl emissions by derivatives of 2,4-di-nitro-phenyl-hydrazine (DNPH) [117–121], Carbonyl emissions lead to formation of secondary organic aerosols (SOA) by forming oligomers [122], Contribution of carbonyls in diesel particles also enhances its responses physiologically [123]. Fig. 21 shows the basic structures of carbonyl group and carbonyl compounds such as Aldehydes and Ketones. 17 carbonyl compounds are listed in Table 11. Aldehydes are a part of the gaseous emission from Cl engines. Acetaldehyde and formaldehyde are probable carcinogens that may also produce other health effects. Aldehydes can be identified by their O ¼CH at the end of a group R of indetermined length, formaldehyde is the simplest (CH2O) [124]. Carbonyls are emitted in both the gas and particle phases [125]. As shown in Table 10, the carbonyl levels in the gas phase are often many times higher than the levels found on PM, and that the mass recovered from diesel-generated particulates is substantially greater than the amount from gasoline [126]. 3.2.10. Nitrogen dioxide, (NO2) Nitrogen dioxide constitutes a part of the NOX emission (it is more toxic than NO and the other component of NOX) it could be anticipated that in the future NO2 may be regulated individually [81]. Nitrogen dioxide (NO2) is a compound that plays a role in respiratory diseases, especially those of asthmatics and children [127]. 3.2.11. Quinones Quinones are a group of organic compounds that consist of diketones (carbonyls) which contain oxygen and are present in both diesel particles and ambient air [128]. Aromatic quinones have previously been identified and measured in gasoline particulate exhaust extracts [128,129]. The origin of the aromatic quinones is not fully understood if it is related to the gasoline fuel as un-combusted quinones (initially in the fuel) or if they are formed in the combustion process. A publication by Xia [130] showed that a quinone-enriched polar fraction from a diesel particulate extract was more potent than PAH with respect to toxic effects in RAW 264.7 cells macrophage-like cells derived from tumors induced in male BALB/c mice by the Abelson murine leukemia virus.

3.2.12. Sulfur dioxide (SO2) Sulfur dioxide from sulfur present in the fuel and the lube oil. Previously fuel sulfur levels were/are at high levels ( 4400 ppm). These levels may still exist in some developing markets. Sulfur dioxide is a precursor of acid rain and atmospheric particulate. The problem of sulfur poisoning has seen much recent attention and not just because of the direct pollution. Automotive catalysts can be rendered ineffective (poisoned) by sulfur, as it deactivates the catalytic sites of the catalyst. This has led to the reduction/elimination of fuel and lube oil sulfur levels by the oil companies and legislative authorities [81]. 3.2.13. Metal oxides and metallic PM Several fuel and engine oil additives include metallic compounds. This results in some metal oxide and elemental emissions, including metals such as; iron, copper, zinc, cerium, calcium (added to the fuel for PM reduction) and phosphorus [131]. Metal oxide emissions and small nano-metallic particulate can be toxic and carcinogenic (most especially nano-particulate) [132]. 3.2.14. Nitrous oxide (N2O) Nitrous oxide (not included in NOX measurements) is a possible future concern as it is promoted in some after-treatment systems for use as an oxidant. As a pollutant it is a powerful greenhouse gas at 298 times the effect of CO2, though how long it would remain as N2O is debatable as it reacts with oxygen to form NO [133]. 3.2.15. Dioxins Dioxins (polychlorinated dibenzodioxins) have lipophilic (dissolve in fats) properties, and are known teratogens (cause birth defects), mutagens, and suspected human carcinogens. This is a large area for research in environmental health thankfully emissions are a problem only when chlorine is present during combustion. Consequently chlorine levels in diesel are now strictly controlled. Potentially biodiesels can contain small levels of chlorine, if certain herbicides are used in production and this must be avoided [134]. The numbers of unregulated emission compounds according to present literature review study are listed in Table 11.

Table 11 Numbers of unregulated emission compounds according to present literature review study. Metal oxides 1 Al 2 Ca 3 Cu 4 5 6 7

Fe Mg Na P

8 S 9 Si 10 Zn 11 12 13 14 15 16 17 18

Inorganic ions

Carbonyl compounds BTEX compounds PAH compounds

Oxy-PAH compounds

Nitro-PAH compounds

Nitrate (NO3
) Nitrite (NO2
) Ammonium (NH4 þ ) Sulfate (SO4
2) Chloride (C1
)

1,3-Butadiene Acetaldehyde Acetone

Ethylbenzene Toluene Benzene

Benz[a]anthracene Benzo[a]pyrene Benzo[b]fluoranthene

1 -Nitropyrene 2-Nitrofluorine 7-Nitrobenz(a)anthracene

Acrolein Benzaldehyde Crotonaldehyde Formaldehyde

o-xylene m/p-xylenes

Benzo[k]fluoranthene Chrysene Dibenz[a,h]anthracene Indeno[1,2,3-c,d] pyrene Acenaphthene Acenaphthylene Anthracene Benzo[ghi]perylene Fluoranthene Fluorine Naphthalene Phenanthrene Pyrene

9-Anthraldehyde Anthraquinone Benz[a]anthracene-7,12dione Anthrone Benzanthone Xanthone

Hexanaldehyde Isovaleraldehyde m/p-Tolualdehyde Methyl ethyl ketone O-Tolualdehyde Propionaldehyde Tolualdehyde Valeraldehyde Methacrolein Butyraldehyde

9-Nitroanthracene 6-Nitrochrysene 1-Nitronaphthalene 2-Nitrobiphenyl 2-Nitronaphthalene 3-Nitrobiphenyl 3-Nitrofluoranthene 3-Nitrophenanthrene 4-Nitrobiphenyl 4-Nitrophenanthrene 6-Nitrochrysene 9-Nitrophenanthrene 1,3-Dinitronaphthalene 1,5-Dinitronaphthalene 1,8-Dinitronaphthalene

Table 12 NOX emission. Used alcohol

Reference fuel

Engine tested

Operation conditions

Test results

Year

Shahad [135]

Ethanol

Gasoline Gasoline with hydrogen enrichment Gasoline

Ethanol blending increased NOX concentrations in the exhaust gases by about 16.18%. NOX concentration was increased for both blends drastically.

Blending up to 30%

Li [138] Ghazikhani [139]

Methanol Ethanol Methanol Ethanol Methanol Ethanol

Different CR and speeds, 5%, 10%, and 15% of blending Using E10 And M10 Blending

2015

Kak [136]

Gasoline Gasoline

Single cylinder, WC, dual fuel, SI engine Single cylinder, air cooled SI engine 1-D model of a 4-stroke SI engine Motorcycles A two stroke gasoline engine

Chauhan [140]

Ethanol

Diesel

Diesel Engine

Various fumigation ratio

Zhang [141]

Diesel

Diesel engine with DOC

Zhang [142]

Methanol Ethanol Methanol

Diesel

4 cylinders DI engine

Zhang [143]

Methanol

Euro V Diesel

Diesel Engine with DOC

10%, 20% and various loads 10%, 20% and engine speed 10%. 20% and

A significant increase in NOX emissions when fuel blends percentage increased up to 30% E30 (M30). The concentration of NOX increased by 76.9–107.7% compared to gasoline. The most advantage of ethanol additives was NOX reduction which was reduced about 83% when it was used in high percentages of ethanol (15%) and averagely 38% for other cases. At overall engine load conditions, NOX decreased up to a certain level of fumigation then increased. Ethanol fumigation increased NOX emission compared to methanol.

Cheng [144]

Methanol

ULSD

Cheng [145]

Methanol

Diesel

Ajav [146]

Ethanol

Diesel

4-cylinder NA, DI diesel engine 4-cylinder NA, DI diesel engine Single cylinder, NA, WC, DI

Hayes [147]

Ethanol

Diesel

turbocharged diesel engine

Broukhiyam [148] Ethanol

Diesel

Heisey [149]

Diesel

5.7 I, v-8, light duty IDI diesel Various fumigation ratio engine Single cylinder DI diesel Various fumigation ratio engine Oldsmobile 5.7 I, V-8 Diesel Various fumigation ratio engine

Iliev [137]

Houser [150]

Methanol Ethanol Methanol

Diesel

15% methanol blends Different speed and percentages of 5%, 10% and 15% blending

30% fumigation And 30% fumigation1920 rpm 30% fumigation

Various fumigation ratio Various fumigation ratio Various fumigation ratio different proofs of alcohol fumigation and engine loads

All level of fumigation gave lower NOX emission than diesel fuel. NOX emission increased with level of fumigation NOX emission decreased compared to Euro V diesel fuel with increasing fumigation concentration. 6.2% and 8.2% decreased in NOX emission using biodiesel with 10% fumigation ethanol compared to ULSD fuel. Methanol fumigation reduced NOX emission compared to baseline diesel fuel. NOX emission increased 0.4% in case of ethanol vaporization (unheated) and 0.7% decreased in case of ethanol preheating compared with diesel fuel. At a load of 0.8 MPa, NOX emission was greater than diesel fuel for higher level of fumigation but NOX decreased within 150 proofs (75% (v/v) EtOH) of ethanol fumigation. NOX decreased with increase in fumigation levels. Methanol and ethanol had approximately same effect on NOX emission. Wet methanol (160 proof) produced a significant reduction in NOX formation. NOX was observed to decrease for all rack settings and speeds as the amount of methanol fumigated was increased

2015 2015 2014 2013

2011 2011 2010 2009 2008 2008 1998 1988

1981 1981

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Author

1980

1457

1458

Table 13 CO emission. Used alcohol

Reference fuel

Shahad [135]

Ethanol

Gasoline

Kak [136]

Li [138]

Methanol Ethanol Methanol Ethanol Methanol Ethanol Methanol

Single cylinder, WC, dual fuel, SI engine Gasoline with hydrogen Single cylinder, air cooled SI enrichment engine Gasoline 1-D model of a 4-stroke SI engine Unleaded gasoline 4-cylinder, 4-strokes SI engine Gasoline motorcycles

Ghazikhani [139]

Ethanol

Gasoline

Surawski [152]

Ethanol

Diesel

A two stroke gasoline engine 4 cylinder diesel engine

Zhang [141]

Diesel

Diesel engine with DOC

Chauhan [140]

Methanol Ethanol Ethanol

Different speed and percentages of 5%, 10% and 15% blending Engine speed 1700 rpm with 4 different engine load conditions and 0%. 10%, 20% and 40% fumigation 10%, 20% and 30% fumigation And various loads

Diesel

Diesel Engine

Various % of fumigation and loads

Tsang [153]

Ethanol

Diesel

4-cylinder NA Diesel engine Various engine loads and fumigation ratio

Zhang [142]

Methanol

Diesel

4 cylinders DI engine

Zhang [143]

Methanol

EuroV Diesel

Diesel Engine withDOC

Cheng [145]

Methanol

Diesel

Cheng [144]

Methanol

ULSD

Cheung [154]

Methanol

ULSD

Iliev [137] Varol [151]

Engine tested

Operation conditions

Test results

Year

Different CR and speeds, 5%, 10%, and 15% of blending Using E10 And M10 Blending

2015

Blending up to 30%

Ethanol blending reduced CO concentration in the exhaust gases by about 45%. With hydrogen enrichment E10 was found to had lower CO specifically at higher loads as compared to M10. When fuel blends percentage increased, the CO concentration decreased.

2015

Blending by mass percent of 10%

Compared with unleaded gasoline, blended fuels had a lower CO.

2014

15% methanol blends

Compared with gasoline fuel, the concentration of CO with M15 decreased by 63%–84%. CO decreased approximately 71% when 15% ethanol added to gasoline. Generally for different speeds and loads, CO decreased averagely 35%. CO emission increased at all loads except idle mode. At idle mode, 15% reduction was achieved by using 10% ethanol. CO emission increased significantly in case of 40% fumigation ethanol at all loads. Ethanol reduced CO emission in the same way like methanol but reduced more CO emission than methanol compared to diesel fuel. At each load condition, CO emission decreased from initial level of fumigation to certain level, respectively, then increased with increasing level of fumigation Increase in CO emission when they applied ethanol fumigation in diesel engine. They observed that CO emission increased by about 0.6 and 1.3 times with 10% and 20% ethanol fumigation at engine load 0.08 MPa and at engine load 0.70 MPa the increase was about 1.8 times compared to diesel engine. Brake specific CO emission increased with increasing fumigation methanol compared to diesel fuel. CO emission increase was 2.7 times. 3.8 times and 5.5 times of baseline value for three consecutive fumigation ratios. CO emission increased significantly with increasing level of fumigation methanol. The increase in CO emission was reported using 10% fumigation methanol. CO emission increased at each engine load with increasing fumigation ratio. Fumigation gave better results than blends. In both cases CO emission increased with increasing ethanol substitution. Ethanol vaporization increased CO emission.

2014

Engine speed 1920 rpm with 5different engine conditions 10%, 20% and 30% fumigation And various loads

Abo- Qudais [155] Ethanol

Diesel

Ajav [146]

Ethanol

Diesel

4-cylinder NA, DI diesel engine 4-cylinder NA, DI diesel engine 4-cylinder NA, Diesel engine Single cylinder DI diesel engine Single cylinder, NA, WC, DI

Various fumigation ratio

Hayes [147]

Ethanol

Diesel

Turbocharged diesel engine

Constant speed of 1800 rpm for three engine loads using fumigation Various engine speeds, blendind and fumigation ratio Ambient air temp. ¼ 20 °C and 50 °C before injection Different proofs of alcohol fumigation

Heisey [149]

Ethanol Methanol

Diesel

Single cylinder DI diesel engine

Engine speed of 2400 and various loads, Various fumigation ratio

Various fumigation ratio

CO emission levels increased greatly as the ethanol flow rate was increased. This was most severe at low loads, Ethanol proof did not have an effect on CO emissions Significant increase in CO emissions at low and medium load at 2400 rpm. At full load condition, CO emissions showed only a slight increased up to the point of 25% alcohol substitution.

2015

2013 2012

2011 2011

2010

2010 2009 2008 2008 2008 2000 1998 1988

1981

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Author

Table 14 HC emission. Used alcohol

Reference fuel

Engine tested

Operation conditions

Test results

Year

Shahad [135]

Ethanol

Gasoline

Methanol Ethanol Methanol Ethanol Methanol

Gasoline with hydrogen enrichment Gasoline

Different CR and speeds, 5%, 10%, and 15% of blending Using E10 And M10 Blending

Ethanol blending reduced UHC concentration in the exhaust gases by about40.15%. With hydrogen enrichment E10 was found to have lower UHC specifically at higher loads as compared to M10. When fuel blends percentage increased, HC concentration decreased.

2015

Kak [136]

Single cylinder, WC, dual fuel, SI engine Single cylinder, air cooled SI engine 1-D model of a 4-stroke SI engine motorcycles

Iliev [137] Li [138] Varol [151]

Gasoline

Ghazikhani [139]

Methanol Ethanol Ethanol

Unleaded gasoline Gasoline

Surawski [152]

Ethanol

Diesel

Zhang [141]

Diesel

Zhang [142]

Methanol Ethanol Methanol

Diesel

Tsang [153]

Ethanol

Euro V Diesel

Zhang [143]

Methanol

EuroV Diesel

Cheng [145]

Methanol

Diesel

Abo-Qudais [155] Ethanol

Diesel

Hayes [147]

Ethanol

Diesel

Schroeder [156]

Methanol

Diesel

Blending up to 30%

2015 2015

Compared with gasoline fuel, the concentration of total hydrocarbons (THC) with 2014 M15 decreased by 11–34.5%. 4-cylinder, 4-strokes SI engine Blending by mass percent of 10% Compared with unleaded gasoline, blended fuels containing different alcohols 2014 appeared to have a lower HC A two stroke gasoline engine Different speed and percentages of Using ethanol reduced HC level in all cases and for each 5% ethanol, HC 2013 5%, 10% and 15% blending approximately 6% decreased. 4-cylinder engine Different loads and fumigation ratio HC emission increased 30% by 20% ethanol substitution at 25% (quarter load) of 2012 maximum load. At half load condition, HC emission increased more than double using 40% ethanol substitution. Diesel Engine with DOC 10%, 20% and 30% fumigation And In case of ethanol fumigation, the reduction of HC emission was more than 2011 various loads methanol since ethanol has lower latent heat of vaporization than methanol 4 cylinders DI engine Engine speed 1920 rpm, Various Methanol fumigation increased the HC emission compared to diesel fuel. 2010 fumigation ratio 4-cylinder NA, Diesel engine Different loads and fumigation ratio An increase of about 1.6 and 3.3 times in BSHC with 10% and 20% fumigation at 2010 engine load 0.08 MPa compared to Euro V diesel fuel while the corresponding increased at 0.70 MPa are 1.1 and 2.4 times compared to diesel fuel. Diesel Engine with DOC different and fumigation ratio Increase of BSHC emission with level of fumigation was higher at low engine load 2009 and lower at high engine load. They found highest increase in BSHC about 7 times at 0.08 MPa and the max reduction was about 3 times at 0.7 MPa compared to diesel fuel. 4-cylinder, NA, DI diesel 10%, 20% and 30% of fumigation HC emission increased with level of methanol fumigation. 2008 engine 2000 Single cylinder DI diesel various engine speeds, blend and Due to ethanol addition to diesel fuel, HC emission increased with increasing engine fumigation ratio engine speed in fumigation and blend methods. Increase in fumigation method was lower than blend method. Turbocharged diesel engine Various fumigations HC emissions increased greatly compared to diesel fuel. HC emission increased 1988 7.2 times from the diesel levels at low load, 6 times at medium load and 3.8 times at high load. Multi-cylinder, turbocharged Changing the diesel injection timing Advancing the injection timing decreased HC levels in the exhaust gas. 1988 diesel engine 15% methanol blends

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Author

1459

1460

Author

Used alcohol

Reference fuel

Engine tested

Operation conditions

Test results

Year

Shahad [135]

Ethanol

Gasoline

Ethanol blending increased CO2 concentrations in the exhaust gases by about 7.5%.

2015

Varol [151]

Methanol Ethanol Ethanol

Unleaded gasoline Gasoline

Different CR and speeds, 5%, 10%, and 15% of blending Blending by mass percent of 10%

Compared with unleaded gasoline, blended fuels containing different alcohols appeared to have a higher rate CO2 By each 5% increasing the ethanol to the fuel, CO2 decreased about 6.3%.

2014

Pannirselvam [157] Ethanol Hebbar [158] Ethanol

Diesel Diesel

Single cylinder, WC, dual fuel, SI engine 4-cylinder, 4-strokes SI engine a two stroke gasoline engine Single cylinder, WC DI diesel engine with EGR

Chauhan [140]

Ethanol

Diesel

Diesel engine

Ciniviz [54]

Methanol

Diesel

Zhang [143]

Methanol

Euro V Diesel

4-cylinder, 4 l CI diesel engine Diesel engine with DOC

Cheng [144]

Methanol

Diesel

Cheung [154]

Methanol

ULSD

Ghazikhani [139]

4-cylinder NA, DI diesel Engine 4-cylinder NA, diesel engine

2013 Different speed, 5%, 10% and 15% blending 2012 various loads– various fumigation ratio Lower CO2 emission using ethanol fumigation compared to base line diesel fuel. Various fumigation ratio using EGR CO2 emission increased with increasing percentage of EGR. They did not find any 2012 considerable change at hot EGR with and without fumigation. Various loads–various fumigation ratio At no load condition, CO2 percentage remains almost constant throughout the level of 2011 fumigation but 20% and 45% load condition, CO2 percentage decreased as ethanol substitution was increased. At full load condition, CO2 percentage decreased up to 15% of fumigation level then increased. They found 15% ethanol fumigation as optimum level of fumigation. Different engine speed and blending The amount of CO2 increased when the methanol amount was increased in the fuel 2011 mixture, 2009 10%. 20% and 30% loads BSCO2 decreased at over all load conditions. At low to medium engine load, the average reduction had been found up to 4.3% for all percentage of fumigation whereas up to 7.2% reduction had been found with 30% fumigation methanol at high engine load. Various fumigation ratio CO2 emission dropped to 2.5% compared to diesel. 2008 Constant speed of 1800 rpm and various loads and fumigation ratio

As the fumigation ratio increased from zero to 0.55, CO2 concentration decreased from 2008 3.47% to 3.21% at 0.19 MPa. When the fumigation ratio increased to 0.6, CO2 emission decreased from 5.55% to 4.99% at 0.38 MPa. At 0.56 MPa, it decreased from 7.96% to 7.59% as the fumigation ratio increases to 0.4.

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Table 15 CO2 emission.

Table 16 PM and Smoke emissions. Used alcohol

Reference fuel Engine tested

Operation conditions

Karavalakis [159]

Ethanol

Gasoline

E10, E15, and E20 blends

Wang [29] Zhang [141]

Ethanol Methanol ethanol

Gasoline Diesel

Chauhan [140]

Ethanol

Diesel

Zhang [142]

Methanol

Diesel

Tsang [153]

Ethanol

Diesel

Surawski [160]

Ethanol

Diesel

Zhang [143]

Methanol

Euro V diesel

Cheng [145]

Methanol

Diesel

Lapuerta [46]

Ethanol

Diesel

Abo- Qudais [155] Ethanol

Diesel

Two 2012 MY vehicles of SI DI engines

Test results

PM mass emissions exhibited decreases as the oxygen content in the fuel increased. In most cases the reductions in PM mass emissions for both vehicles were statistically significant. A single-cylinder DISI engine Deferent speeds, blends and IMEP PM emissions from ethanol were lower than those from gasoline. diesel engine with DOC 10%, 20% and 30% fumigation and various Methanol fumigation caused lower PM emission than ethanol fumigation loads and reduction was 15–32% and 20–41% for 10% and 20% fumigation methanol and 9–19% and 7–26% for 10% and 20% fumigation ethanol. They also observed that PM decreased with increasing ethanol fumigation like methanol. Diesel engine Various fumigation ratio and loads Smoke opacity decreased as ethanol fumigation increased. At higher load of 70% and 100%, smoke opacity decreased very quickly up to 14% ethanol fumigation then reduction was lightly. 4 cylinders DI engine 10%,20% and 30% fumigation at the engine For all fumigation ratios, PM emission decreased compared to diesel fuel. speed of 1920 rpm with five steady conditions They observed that reduction was more significant at medium load with all percentage of fumigation. About 14–31% reduction was measured with 10% fumigation methanol when reduction was about 27–57% with 30% fumigation ethanol. 4-cylinder NA, diesel engine Various loads and fumigation ratio Fumigation reduced smoke opacity and PM emission compared to diesel fuel. Smoke opacity increased with increasing engine load with all levels of fumigation but no significant change was found at low engine load. At medium and high loads, significant change in smoke opacity reduction was achieved with all levels of fumigation. In both cases neat diesel used having 10 ppm sulfur and ethanol having 4-cylinder engine At 2000 rpm with full load and at inter0.55% moisture denatured with 1% unleaded petrol. Their results showed mediate speed 1700 rpm with 4 different that ethanol fumigation significantly reduced PM emission especially at fullloads load operation during the E40 test. At half or quarter load. PM reduction was not satisfying compared to full-load. Diesel engine with DOC 10%, 20% and 30% fumigation and various No significant change was found in smoke opacity and PM concentration at loads low loads but at medium and high engine load condition, remarkable reduction was found compared to diesel fuel. Maximum 58% smoke reduction was found with 30% fumigation methanol at the engine load of 0.58 MPa. 4-cylinder NA, DI diesel engine Various fumigation ratio Methanol fumigation reduced smoke opacity and PM emission in comparison with diesel fuel. They found average reduction in particulate mass concentration is about 25% for 10% fumigation methanol. But maximum reduction was 49% at higher level of fumigation. 4-cylinder, 4-stroke, turbo-charged, 0% and10% ethanol percentage of blending The amount of PM and smoke decreased with using ethanol compared to intercooled, DI diesel engine diesel. Single cylinder DI diesel engine Various speeds and fumigation ratio They measured maximum decrease in smoke opacity and soot mass concentration of 48% and 51% for 20% ethanol fumigation whereas for ethanol– diesel blend the maximum reduction was measured as 33.3% and 32.5% at 15% ethanol blend.

Year 2014

2014 2011

2011

2010

2010

2009

2009

2008

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Author

2008 2000

1461

1462

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

4. Results of regulated emissions NOX, CO, HC, CO2, PM and smoke are the regulated emissions which are listed in present literature review work. The results of different studies about regulated emissions are summarized in Tables 12–16. It can be found from Tables 12–16 that application of alcohol as an alternative fuel in fumigation mode in IC engines lead to reduction of NOX and CO2 in most tests and PM in all cases. However, an increase of CO and HC is observed with using alcohol in fumigation mode in most cases. It is noticeable that a diverse effect of alcohol application in blended mode compared to fumigation mode on regulated emissions except PM is recorded in considerable tests.

5. Results of unregulated emissions In the part of the effect of alcohols on unregulated emissions of IC engines, 19 experimental works which had done by different researchers since 1983–2014 are selected to analyze for this literature review study. The test engine and fuel, emissions testing and analysis, results and summary of different works are the following: 5.1. G. Karavalakis and co-workers (2014) The goal of the Karavalakis's study et al. [159] was to examine how ethanol/gasoline blends and iso-butanol gasoline blends impact the criteria emissions, gaseous air toxic pollutants, and PM emissions from two modern technology light-duty gasoline vehicles fitted with DI stoichiometric engines. However, the influence of different ethanol/gasoline blends on unregulated emissions is only mentioned in the present literature review study. 5.1.1. Test experimental setup and fuels The test matrix included two 2012 model year (MY) passenger cars equipped with wall-guided direct injection fueling with stoichiometric combustion. Both vehicles were also fitted with a three-way catalyst (TWC). The first vehicle (Kia Optima) was a 2.4 L, 4 cylinders DI engine, having a rated horsepower of 200 hp at 6300 rpm. The second vehicle (Chevrolet Impala) was a 3.6 L, 6 cylinders DI engine, having a rated horsepower of 300 hp at 6500 rpm. The Kia Optima and the Chevrolet Impala had 11,824 and 25,372 miles, respectively, at the start of the test campaign. The Kia Optima was certified to the Federal Tier 2, Bin 2 emission standards, while the Chevrolet Impala was certified to California LEV II, SULEV emission standards. It should be noted that not every vehicle was tested on all fuels. Only the 2012 Kia Optima was tested on the E10/Bu8 mixture. A total of seven fuels were employed in the authors’ work. The fuel test matrix included an E10 fuel (10% ethanol and 90% gasoline), which served as the baseline fuel for their study, and two more ethanol blends, namely E15 and E20. For their study, isobutanol was blended with gasoline at proportions of 16 (Bu16), 24 (Bu24), and 32% (Bu32) by volume, which were the equivalent of E10, E15, and E20, respectively, based on the oxygen content. In addition, an alcohol mixture consisting of 10% ethanol and 8% isobutanol (E10/Bu8) was used. This mixed alcohol formulation was equivalent to E15 based on the oxygen content. All fuels were custom blended to match the oxygen contents, maintain the Reid vapor pressure (RVP) within certain limits (6.4–7.2 psi), and match the fuel volatility properties, except the E10/Bu8 fuel that was a 50/50 splash blend of the E20 and Bu16 fuels.

5.1.2. Emissions testing and analysis All tests were conducted in CE-CERT's Vehicle Emissions Research Laboratory (VERL), which was equipped with a Burke E. Porter 48-inch single-roll electric dynamometer. A Pierburg Positive Displacement Pump-Constant Volume Sampling (PDP-CVS) system was used to obtain certification-quality emissions measurements. For all tests, standard bag samples for carbonyl analysis were collected through a heated line onto 2,4-dinitrophenylhydrazine (DNPH) coated silica cartridges (Waters Corp., Milford, MA). Sampled cartridges were extracted using 5 mL of acetonitrile and injected into an Agilent 1200 series high performance liquid chromatograph (HPLC) equipped with a variable wavelength detector. The column used was a 5 pm Deltabond AK resolution (200 cm*4.6 mm ID) with upstream guard column. They reported that the HPLC sample injection and operating conditions were set up according to the specifications of the SAE 930142HP protocol [161]. Samples for 1,3 butadiene, benzene, toluene, ethylbenzene, and xylenes were collected using Carbotrap adsorption tubes consisting of multi-beds, including a molecular sieve, activated charcoal, and carbotrap resin. An Agilent 6890 GC with a FID maintained at 300 °C was used to measure volatile organic compounds. A Gerstel TDS thermal adsorption unit was used for sample injection. This unit ramps the temperature from 30 °C to 380 °C at a rate of 6 °C per minute to desorb the sample from the tubes. A 60 m * 0.32 mm HP-1 column was used. For these analyses, the GC column and operating conditions were set up according to the specifications of SAE 930142HP Method-2 for C4–C12 hydrocarbons. 5.1.3. Results and discussion The study's aim was to identify and quantify 13 aldehydes and ketones in the exhaust of both vehicles when operated with alcohol formulations. Figs. 22 and 23 show the carbonyl emissions for the Kia Optima and Chevrolet Impala, respectively, expressed in mg/mile. For both SI DI vehicles, formaldehyde and acetaldehyde were the most abundant compounds in the tailpipe followed by butyraldehyde, benzaldehyde, crotonaldehyde, methacrolein, and propionaldehyde. Other carbonyl compounds were also present in the exhaust but in lesser amounts, including those of methyl ethyl ketone (MEK), valeraldehyde, and hexanaldehyde. Hexanaldehyde was detected in small concentrations

Fig. 22. Individual carbonyl compounds for the Kia Optima over the FTP cycle. Errors bars represent7 one standard deviation around the average value for each fuel [159].

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Fig. 23. Individual carbonyl compounds for the Chevrolet Impala over the FTP cycle. Errors bars represent 7one standard deviation around the average value for each fuel [159].

for some fuel blends and its mainly decreased by the addition of oxygenates in gasoline. Tolualdehyde was undetectable for all fuel blends and for both test vehicles. Acetaldehyde is classified as probably carcinogenic whereas formaldehyde is classified as human carcinogen by the U.S. Department of Health and Human Services. For both vehicles, a clear reduction in formaldehyde and acetaldehyde emissions was observed with E15 relative to E10. For the Chevrolet Impala, an increase in both formaldehyde and acetaldehyde emissions was seen for E20 relative to E10 blend but not at a statistically significant level. On the contrary, for the Kia Optima, E15 and E20 blends showed marked and statistically significant reductions in both formaldehyde and acetaldehyde emissions relative to E10. For formaldehyde, these reductions were 74% and 88% for E15 and E20, respectively, while for acetaldehyde the reductions were 72% and 82% for E15 and E20, respectively. Generally, gasoline fuels do not contain carbonyl compounds, with the emissions of aldehydes and ketones being a result of partial oxidation of the fuel components during combustion. The authors compared their results with previous studies which had shown that the addition of ethanol fuels can produce higher formaldehyde and acetaldehyde emissions [162–164]. According to their results, the butanol blends and the alcohol mixture (E10/Bu8) showed higher butyraldehyde emissions than the ethanol blends for both vehicles. It was reported that, benzaldehyde, which is primarily produced from fuel aromatic hydrocarbons, showed mixed trends with the alcohol fuels for both vehicles. For the Kia Optima, benzaldehyde emissions for E15 were higher relative to E10, while E20 was lower. The alcohol mixture was at about the same levels with those of E15. For the Chevrolet Impala, both higher ethanol blends trended lower in benzeldehyde emissions compared to E10. Their results were in agreement with those showing that the addition of oxygenates decreased benzaldehyde emissions [165,166,163], but consistent with other studies showing some increase in benzaldehyde emissions probably because of the enhancement of aromatics oxidation [167,168]. Authors analyzed their data in Figs. 24 and 25 which indicate the cumulative 1,3-butadiene, benzene, ethylbenzene, toluene, m, p-xylene, and o-xylene emissions over the FTP cycle for the Kia Optima and the Chevrolet Impala, respectively. These emissions

1463

Fig. 24. 1,3-Butadiene and BTEX emissions for the Kia Optima over the FTP cycle. Errors bars represent 7one standard deviation around the average value for each fuel [159].

Fig. 25. 1,3-Butadiene and BTEX emissions for the Chevrolet Impala over the FTP cycle. Errors bars represent 7one standard deviation around the average value for each fuel [159].

were measured cumulatively over the entire cycle and were not weighted like the traditional regulated gaseous emissions. They reported that the aromatic hydrocarbons of benzene, ethylbenzene, toluene, m/p-xylene, and o-xylene were usually termed as BTEX. The most reactive volatile organic compounds (VOCs) from internal combustion engines are BTEX compounds, since they contain a C¼ C bond, that can add free radicals. In general, BTEX emissions for the Kia Optima were found significantly higher than those for the Chevrolet Impala, following similar trends with the THC emissions for these vehicles. Overall, They found that 1,3-butadiene and BTEX emissions did not follow a uniform trend for both vehicles and showed both increases and decreases with the use of oxygenated fuels. For the Kia Optima, E15 and E20 increased 1,3-butadiene emissions by 53% and 199%, respectively, relative to E10 blend, with the increase for E20 being statistically significant. This is an important finding since 1,3-butadiene is one of the air toxics of interest and a recognized human carcinogen. In contrast to the results observed for the Kia Optima, for the Chevrolet Impala 1,3-butadiene emissions trended lower for E15 and E20 relative to E10 but not at a statistically significant level.

1464

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Benzene is one of the major toxic species emitted in tailpipe emissions and a suspected carcinogen. The authors mentioned that some increases were seen in their results for both vehicles in benzene emissions with the use of higher ethanol blends. This phenomenon was more pronounced for the Kia Optima where the increase in benzene emissions for E15 and E20 relative to E10 were 47% and 112%, respectively, and also statistically significant. For the Chevrolet Impala, there was a statistically significant 69% increase in benzene emissions for E15 compared to E10, whereas E20 produced similar levels of benzene emissions with E10 blend. Ethylbenzene was the highest emission among the target air toxics for all vehicles/fuel combinations. For the Kia Optima, ethylbenzene emissions showed a marked increase for E15 (148%) and E20 (136%) blends compared to E10 at a statistically significant level. Toluene emission exhibited some increases with E15 (117%) and E20 (224%) compared to E10 for the Kia Optima. The increase in toluene emissions for E20 relative to E10 was statistically significant level. As they expected, toluene emission levels for E15 and E10/Bu8 were about the same for the Kia Optima. For the Chevrolet Impala, the higher ethanol blends did not show any strong trends in toluene emissions. It was expected that a reduction in toluene emissions would have occurred with increasing oxygen content and with the reduction in aromatics content in the fuel. The results of that study indicated that toluene may have a different production pathway in SIDI engines other than through the aromatics in the fuel. Tests results indicated that xylene emissions followed similar patterns with toluene emissions for both vehicles. For the Kia Optima, E15 and E20 trended higher than E10, with E20 showing a statistically significant increase in m/p/o-xylenes emissions. Higher xylene emissions were also seen for the E10/Bu8 blend relative to E10 at a statistically significant level with E10/Bu8 having about the same emission levels as E15. For the Chevrolet Impala, the ethanol blends did not present any significant fuel trends. 5.1.4. Summary Karavalakis and co-workers examined the effect of fuel formulation on the criteria emissions, gaseous air toxic pollutants, and particle emissions from two modern technology gasoline passenger cars equipped with direct injection fueling. A total of seven alcohol fuel formulations were utilized, including ethanol blends (E10, E15, and E20), iso-butanol blends (Bu16, Bu24, and Bu32), and an alcohol mixture comprised of 10% ethanol and 8%

iso-butanol (E10/Bu8). The two 2012 MY vehicles tested over the FTP cycle on a light-duty chassis dynamometer were equipped with stoichiometric, wall-guided SI Dl engines with TWCs. The conclusions drawn from that study are the following points:

 Formaldehyde and acetaldehyde were the predominant

 

  

carbonyls in the exhaust for both vehicles followed by butyraldehyde, benzaldehyde, crotonaldehyde, methacrolein, and propionaldehyde. Formaldehyde and acetaldehyde increased and decreased with the higher ethanol blend relative to E10. Emissions of 1,3-butadiene did not follow a global trend between the test fuels for both vehicles, showing statistically significant increases for the higher ethanol blends relative to E10 for the Kia Optima. Benzene emissions showed elevated emissions for the higher ethanol blends. For the Kia Optima, E15 and E20 blends led to higher ethylbenzene, toluene, and xylenes emissions compared to E10. For the Chevrolet Impala, the higher ethanol resulted in minimal differences in ethylbenzene, toluene, and xylenes emissions compared to E10.

5.2. Ch. Wang (2014) Wang et al. [29] investigated the combustion characteristics and emissions of ethanol and two other novel biofuel candidates, 2-methlyfuran (MF) and 2,5-dimethylfuran (DMF) in a sprayguided GDI engine. However, the effect of ethanol on unregulated emissions is only presented in this literature review study. 5.2.1. Test experimental setup and fuels In author's experiment thesis, the engine and instrumentation setup (Fig. 26) consisted of a direct current (DC) dynamometer, single cylinder spray guided DISI research engine, control, data acquisition and recording system as shown in Fig. 26. He conducted the experiment on an engine which was coupled to a DC dynamometer that was capable of maintaining engine at a fixed speed (resolution: 71 rpm) regardless of the engine power output. The dynamometer was used as an engine starter when the engine starts and as a load absorber when the engine was fired. A 100 L intake buffer box made of steel was used to reduce intake flow oscillation introduced by the single cylinder engine, which improved the volumetric efficiency and the accuracy of air flow rate measurement. The engine was operated via a Lab VIEW

Fig. 26. Schematic of engine and instrumentation setup [29].

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

program. The controllable parameters included injection timing and pulse width, injection mode (DI or PFI, or dual-injection mode), ignition timing and ignition energy, intake and exhaust valve timing. The throttle was manually controlled via a cable. The 4-valve, 4-stroke single-cylinder close-space concept (spray-guided) DISI research engine is shown in Fig. 27. The technical data and engine specification are listed in Table 17. The engine had a geometric compression ratio (CR) of 11.5, which could be changed by adjusting the number and the size of metal blocks between the crankcase and cylinder block. However the increase of CR was limited due to the risk of intake valves hitting the piston crown. The engine featured a modem sprayguided direct-injection (SGDI) cylinder head as a single cylinder version of Jaguar AJ133 (V8) engines. The engine had compact double overhead camshafts (DOHC) and equipped with variable valve timing (VVT) systems in both intake and exhaust sides enabling a 50 CAD valve timing adjusting window. The engine was equipped with both DI (150 bar) and PFI (3 bar) injection systems. The author conducted his experiment base on Gasoline, ethanol, 2-Methylfuran (MF) and 2,5-Dimeihylfuran (DMF). Gasoline and ethanol were supplied by the Shell Global Solutions, UK. MF was supplied by the Fisher Scientific, UK. DMF was supplied by the Shijiazhuang Lida Chemical Co. Ltd. and the Beijing LYS Chemicals Co. Ltd. with a purity of 99%. But ethanol is chosen to investigate for this literature review study.

used for aldehyde emissions measurement. The specifications of HPLC is shown in Table 18. In that study, carbonyls also were analyzed by using HPLC. The raw exhaust sample was bobbling into a glass (20 mL DNPH solution) immersed in an ice bath (Fig. 28). The aldehyde components in the exhaust reacted with DNPH (Fig. 29) and the DNPHderivative products were retained in the solvent. The solvent then was analyzed by HPLC. The engine was firstly run for at least 20 min, using the PFI injection system. When the coolant and oil temperatures stabilized at 358 K, the engine was considered to be warm and then GDI injection system was switched on to replace the PFI injection system. For all of the tests, the exhaust temperature was monitored as an important indicator of stable test conditions. All of the tests were carried out at ambient air intake conditions (2987 1 K), at the engine speed of 1500 rpm and stoichiometric air/fuel ratio Table 18 Specifications of HPLC [29]. Separation Detection Column Sample Injection size Flow rate Test conditions Test duration

Shimadzu LC20 Shimadzu SPD-M20A Luna: 250 4.6 mm  5 mm DNPH (20 mL) 25 mL lmL/min 10:90–70:30 v/v; MeCN/water, 120 min; UV λ ¼ 360 nm 130 min

5.2.2. Emissions testing and analysis The emissions which were measured in the thesis were gaseous emissions, PM emissions, and aldehyde emissions. HPLC was

Fig. 27. Single cylinder GDI engine [29].

Fig. 28. Sample collection set up [29].

Table 17 Engine specification [29]. Engine type Combustion system Swept volume Bore  stroke Connecting rod length Geometric CR. Injection system Intake valve opening Exhaust valve closing

1465

4-Stroke, 4-valve Spray guided DISI/PFI 565.6 cm3 90  88.9 mm2 160 mm 11.5:1 Dl (150 bar) and PFI (3 bar)
25° to 25° aTDC 0–50° aTDC Fig. 29. Reaction scheme [29].

1466

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

(AFR). The test conditions for Carbonyls emissions are listed in Table 19. Aldehydes were measured using a HPLC (model: Shimadzu LC20). The aldehydes were measured including formaldehyde, acetaldehyde, acrolein, propionaldehyde, methacrolein, benzaldehyde, valeradehyde, m-tolualdehyde and hexaldehyde. The samples were bubbled at 1 L/min for 20 min in an acidified 2,4-dinitrophenylhydrazine (DNPH) reagent (20 mL). The reaction of carbonyls with the DNPH reagent forms DNPH-carbonyl derivatives, which was analyzed then by HPLC. 5.2.3. Results and discussion It can be seen from Fig. 30 that formaldehyde and C3–C6 aldehyde emissions of ethanol were recorded less than gasoline. But acetaldehyde emissions of ethanol was observed more than gasoline. The author showed the aldehyde emissions of MF, DMF, gasoline, and ethanol at 6.5 bar IMEP in Fig. 30. He observed that formaldehyde emission of ethanol was lower than that of gasoline but higher than MF and DMF. Acetaldehyde emission of ethanol was higher than gasoline, MF and DMF. The concentrations of aldehydes ranging from C3 to C6 were relatively lower compared with formaldehyde and acetaldehyde. The overall aldehyde emissions of MF (89 ppm) and DMF (104 ppm) were considerably lower than those of gasoline (258 ppm) and ethanol (462 ppm). The total aldehyde emissions accounted for 4.6%, 4.7%, 9.2% and 25.1% of total HC emissions for MF, DMF, gasoline and ethanol, respectively. 5.2.4. Summary The tests were performed on a 4-valve, 4-stroke single-cylinder close-space concept (spray-guided) DISI research engine with a fixed compression ratio of 11.5:1. The author conducted his experiment base on Gasoline, ethanol, 2-Methylfuran (MF) and 2,5-Dimeihylfuran (DMF). The main summaries are the following:

 Formaldehyde and C3–C6 aldehyde emissions of ethanol were less than gasoline. Table 19 Engine test conditions and test equipment [29]. Emissions Tested fuels

IMEP (bar)

Spark timing (°bTDC)

Emission measurement equipment

Carbonyls

6.5

KLSA/MBT

HPLC

MF,DMF, ULG,ETH

 Acetaldehyde emissions of ethanol were more than gasoline.  Formaldehyde emission of ethanol was lower than that of gasoline but higher than MF and DMF.

 Acetaldehyde emission of ethanol was higher than gasoline, MF and DMF.

 Overall aldehyde emissions of ethanol were considerably higher than those of gasoline, MF and DMF. 5.3. Li and co-workers (2014) The emission characteristics of motorcycles using gasoline and M15 (consisting of 85% gasoline and 15% methanol by volume) were investigated in an article [138]. Exhaust and evaporative emissions, including regulated and unregulated emissions, of three motorcycles were presented in that paper. But, the impact of methanol blends on unregulated emissions compared to gasoline is only summarized in present literature review study. 5.3.1. Test experimental setup and fuels Their experiments were performed on three motorcycles in a national emission certification laboratory with excellent quality control and sample management system. Because the actual emissions of in-use motorcycles are affected by many factors (such as age, mileage, and maintain and inspection), the motorcycles studied in their paper were selected from the enterprises' certification test products. The selected motorcycles were produced by typical enterprises and enjoyed the most sales in China. They were also in good shape with good emission stability and repeatability and could meet the experiment requirements for emission contrast between different fuels. Technical data of the three motorcycles are shown in Table 20. Two fuels were used: commercial 93# (research octane number) gasoline and M15 methanol gasoline. The commercial 93# gasoline complied with China fourth-stage fuel standard which equal to Euro 4. M15 methanol gasoline was made by mixing the commercial 93# gasoline with industrial grade methanol in fraction of 15% by volume. 5.3.2. Emissions testing and analysis Fig. 31 shows the schematic diagram of the measurement system for motorcycle exhaust emissions. The exhaust gas was diluted with indoor air by the CVS system (CVS-7100, Horiba, Japan) and collected to the sampling bags. According to U.S. Environmental Protection Agency (EPA) technical standard TO-11A (EPA/625/R-96/010b), carbonyls were collected by air sampling pump using tubes coated with 2, 4-dintrophenylhydrazine (DNPH) (Supelco, USA). In order to ensure that the carbonyls could fully Table 20 Specifications of the test motorcycles [138]. Items

Value A

Engine type

Fig. 30. Formaldehyde and acetaldehyde and total C3–C6 aldehyde emissions for MF and other tested fuels at 6.5 bar IMEP [29].

Tank volume (L) Displacement (mL) Borexstroke (mm  mm) Rated power at engine speed (kW/rpm) Maximum torque at engine speed (N m/ rpm) Odometer (km) After-treatment Engine fuel system

B

C

Single-cylinder, 4-stroke, water-cooling, 2 valves per cylinder 4 12 12 110 125 150 52.4  49.5 54  54 62  49.5 5.3/7500 7.1/7800 8.3/8000 8.0/4500

8.0/6000

11.4/6000

1253 TWC Carburetor

1570 TWC Carburetor

1405 TWC Carburetor

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

1467

Fig. 31. Schematic diagram of the measurement for motorcycle exhaust emissions [138].

react with 2-4 DNPH, sampling flow and time were set for 1000 mL/min and 20 min, respectively. After extracted by acetonitrile, 14 kinds of carbonyls in the sample were measured by high performance liquid chromatography (HPLC) (HPLC1200, Agilent, USA), namely, formaldehyde, acetaldehyde, acrolein, acetone, propionaldehyde, crotonaldehyde, methyl ethyl ketone, methacrolein, butyraldehyde, benzaldehyde, valeraldehyde, tolualdehyde, cyclohexanone and hexanaldehyde. VOCs are defined as the general term for all the organic compounds whose boiling points were between 323 K and 633 K under the normal pressure. In their paper, the targets VOCs contained benzene, toluene, ethylbenzene, m-xylene, p-xylene, o-xylene, styrene, n-butylacetate, and n-undecane. According to the US Environmental Protection Agency (EPA) technical standard TO-17 (EPA/ 625/R-96/010b), VOCs were collected by air sampling pump using stainless steel sorbent tubes coated with Tenax TA (Markes, UK). In order to ensure that the VOCs can fully absorbed by Tenax TA, sampling flow and time were set for 500 mL/min and 20 min respectively. After thermal desorbed (TD), nine kinds of VOCs were measured by gas chromatography mass spectrometer (GC–MS)(GC–MS, Agilent, USA). Both of carbonyls and VOCs were identified by matching retention time with those of commercial standard mixtures (Supelco, USA) and quantified by using five-point external standard methods in their work. During each test, the unregulated emissions in the diluted air were sampled and analyzed as the blank values, which were subtracted from samples. 5.3.3. Results and discussion The unregulated emission results indicated that the amounts of the emitted methanol were quite few when comparing with carbonyls and VOCs. Most of methanol can be completely burnt in the cylinders for its higher oxygen content and faster flame propagation velocity. Thus they paid more attentions to carbonyls and VOCs in the exhaust emission. Eight kinds of carbonyls detected and the total carbonyls from exhaust emissions are listed in Table 21. It is obvious that the amounts of formaldehyde and acetaldehyde are the dominant among carbonyls analyzed by HPLC. Formaldehyde can cause respiratory dysfunction, hepatic toxic lesions and carcinogenicity, so their paper focused on the results of formaldehyde and total carbonyls from exhaust emissions. Since it was much easier for methanol to generate formaldehyde than gasoline did, motorcycle fueled with M15 emitted 16.4–52.5% more formaldehyde than that motorcycle fueled with gasoline did. However, they found that

Table 21 The carbonyls from exhaust emissions (unit: mg/km) [138]. A

Formaldehyde Acetaldehyde Acrolein þacetone Propionaldehyde Crotonaldehyde Methyl ethyl ketone Benzaldehyde Carbonyls

B

C

Gasoline

M15

Gasoline

M15

Gasoline

M15

0.226 n.a. 0.299 n.a. n.a. 0.608 n.a. 1.133

0.347 1.130 0.313 0.179 n.a 0.842 0.630 3.441

0.483 n.a. 0.203 n.a. n.a. 0.464 n.a. 1.150

0.562 0.875 0.270 0.139 n.a. 0.710 0.736 3.292

0.364 n.a. 0.266 0.137 n.a. 0.547 n.a. 1.314

0.604 1.216 0.362 n.a 0.063 0.870 0.814 3.929

n.a. means that the pollutants have not been detected.

Table 22 VOCs from exhaust emissions (unit: mg/km) [138]. A

Benzene Toluene n-Butylacetate Ethylbenzene p,m-Xylene Styrene o-Xylene n-Undecane VOCs

B

C

Gasoline

M15

Gasoline

M15

Gasoline

M15

15.185 94.322 0.022 10.776 11.883 15.113 40.360 0.167 187.828

10.725 58.002 0.071 19.218 23.334 9.588 31.860 4.279 157.076

11.167 93.078 0.033 10.803 26.276 10.625 24.539 3.075 179.595

8.091 63.875 0.040 19.784 14.849 6.721 15.668 1.453 130.481

8.158 42.101 0.019 14.686 12.878 6.341 12.286 1.101 97.570

3.326 23.077 0.009 5.650 4.837 0.726 2.268 0.033 39.925

both of the formaldehyde for M15 and gasoline were far lower than the formaldehyde limit value of 15 mg/mile in the EPA exhaust emission standard. The total carbonyls increased by three times when compared with gasoline fueling motorcycles, because the additives in M15 contain other polymeric alcohol to ensure the mutual solubility of methanol and gasoline, which may produce acetaldehyde in the process of combustion or in the catalyst. Nine kinds of VOCs from exhaust emissions were analyzed by GC–MS and the results are listed in Table 22. They reported that due to the difficulties in resolving the chromatography peaks, the results for m-xylene and p-xylene were represented as a sum. BTEX (benzene, toluene, ethylbenzene, p,m,o-xylene) dominating VOCs accounted for more than 90%, especially the toluene accounting for approximately 50% of VOCs whatever the motorcycle was fueled with, gasoline or M15. BTEX from motorcycles

1468

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

fueled with M15 decreased by 16–60% compared with that from gasoline fueling motorcycles, because the higher levels of unsaturated hydrocarbons (including olefins, aromatics and benzene in gasoline) made it easier to perform nucleation, condensation reaction, which contributed to the formation of VOCs. 5.3.4. Summary An experiment was performed on three motorcycles in a national emission certification laboratory with excellent quality control and sample management system. Two fuels were used; commercial 93# (research octane number) gasoline and M15 methanol gasoline. The conclusions drawn from that study are the following points:

 Formaldehyde was the main pollutant among the total carbonyls emitted from vehicles both fueled with gasoline and M15.

 The carbonyls from exhaust emissions of M15 were more than gasoline.

 Motorcycles fueled with M15 emitted 16.4–52.5% more formaldehyde than gasoline fueling motorcycles.

 The totality of BTEX decreased by 16–60% with using M15.  Controlling the concentration of formaldehyde in the exhaust emissions can make methanol more popular as a kind of alternative fuel. 5.4. G. Karavalakis and co-workers (2012) The impact of ethanol blends on criteria emissions (THC, NMHC, CO, NOX), greenhouse gas (CO2), and a suite of unregulated pollutants in a fleet of gasoline-powered light-duty vehicles was investigated in [166]. But, the influence of ethanol on unregulated pollutants is only summarized in the present literature review work. 5.4.1. Test experimental setup and fuels A total of six fuels were employed in their experimental work. The fuel test matrix included a CARB phase 2 certification fuel with 11% MTBE (CARB 2) and a CARB phase 3 certification fuel with 5.7% ethanol (CARB 3). CARB 2 served as the base fuel for comparisons, as it was the fuel currently used for certification. CARB 3, with 5.7% ethanol, was used as the base fuel for creating blends with ethanol at proportions of 10 (E10), 20 (E20), 50 (E50), and 85% (E85) by volume. The test matrix included seven vehicles, selected from three categories, based on their technology. Two vehicles (1984 Toyota pickup and 1985 Nissan 720 pickup) were from the Tech 3 category (1981–1985), having early three-way catalysts (TWC) with closed loop fuel control. Two vehicles (1991 Ford Explorer and 1993 Ford Festiva) were from the Tech 4 category (1986– 1995), while three vehicles (1996 Honda Accord, 2000 Toyota Camry, and 2007 Chevy Silverado) were from the Tech 5 (1996– 2010) category. In the Tech 5 category, one of the vehicles (2007 Chevy Silverado) was a Flexible Fuel Vehicle (FFV), which could be operated on fuels containing 85% ethanol by volume. The chosen vehicles were representative of the vehicle fleet in the State of California. The Tech 3 and Tech 4 vehicles were tested on a four fuel test matrix including the CARB Phase 2 certification fuel, the CARB Phase 3 certification fuel, E10 and E20. The FFV was tested on a six fuel test matrix including E50 and E85 ethanol blends in addition to CARB 2, CARB 3, E10 and E20. 5.4.2. Emissions testing and analysis Emissions of carbonyl compounds, 1,3-butadiene, and BTEX were performed in accordance with protocols developed as part of the Auto/Oil Air Quality Improvement Research Program [161], with enhancements. Samples for BTEX and 1,3-butadiene were collected using Carbotrap adsorption tubes consisting of multibeds including a molecular sieve, activated charcoal, and carbotrap

resin. For BTEX and 1.3-butadiene, the GC sample injection, column, and operating conditions were set up according to the specifications of SAE 930142HP Method-2 for C4–C12 hydrocarbons. An HP 5890 Series II GC with a flame ionization detector (FID) maintained at 300 °C was used to measure BTEX and 1,3 butadiene. A 2 m*0.32 mm deactivated fused silica BTEX and 1,3-butadiene. A 2 m*0.32 mm deactivated fused silica pre-column and a 60 m*0.32 mm HP-1 column were used. Samples for carbonyl analysis were collected through a heated line onto 2,4dinitrophenylhydrazine (DNPH) coated silica cartridges (Waters Corp., Milford, MA). 5.4.3. Results and discussion Carbonyl emissions (aldehydes and ketones) were obtained from two of the seven vehicles. A total of 13 carbonyls were identified and quantified in the exhaust. Fig. 5a and b show the carbonyl compounds emitted from the 1996 Honda Accord (a) and the 2007 FFV Chevrolet Silverado (b). They reported that consistent with previous findings [120,164,169,170], formaldehyde, acetaldehyde, and acetone were the most prominent carbonyl compounds for both vehicles. High molecular weight carbonyl compounds were also presented, but in significantly lower amounts. For the 1996 Honda Accord, emission levels of acrolein, propionaldehyde, valeraldehyde, tolualdehyde, and hexanaldehyde were below the detection limits of the method for all test fuels. For the FFV, in addition to the above compounds, crotonaldehyde, MEK, and methacrolein were almost undetectable. However, only tolualdehyde was found in detective levels for the E85 fuel. For toxic emissions, acetaldehyde showed the most consistent trend, increasing with ethanol content for both vehicles. For the 1996 Honda Accord, acetaldehyde emissions increased for the E10 blend by 71% and 98%, while E20 increased 202% and 251%, compared with CARB 2 and CARB 3. For the 2007 Chevy Silverado, significant increases in acetaldehyde were only seen with the use of the E85 fuel, with increasing on the order of 1097% (compared to CARB 2) and 1430% (compared with CARB3). Acetaldehyde emissions for E10 were
39% and
23% lower than CARB 2 and CARB 3. The changes in acetaldehyde emissions for E20 and E50 were within the experimental variability. Their results were in agreement with other studies. For instance previous studies had generally shown consistent increased in acetaldehyde emissions with increasing ethanol content [171–177], as ethanol was the main precursor of acetaldehyde in vehicular emissions. For the 2007 Chevrolet Silverado, the blends of E10, E20, and E50 resulted in reductions in formaldehyde emissions, when compared to CARB 2. The reductions were
44% for E10,
36% for E20, and
27% for E50. Compared to CARB 3, only E10 resulted in limited reductions (
5%) of formaldehyde emissions, while E20 and E50 increased emissions by 8–23%, respectively. The use of E85 resulted in significant increases in formaldehyde emissions 88% increase when compared to CARB 2 and 216% increase when compared with CARB 3. They indicated that the increase formaldehyde emissions for E85 might be attributed to the presence of ethanol, and the higher oxygen content in the fuel, as well as decreases in fuel aromatics, because these compounds do not participate in formaldehyde formation [167]. For the 1996 Honda Accord, the use of CARB 3 resulted in 14% decrease in formaldehyde emissions, when compared with CARB 2, with E10 following closely behind showing 10% reduction, though the reductions were not statistically significant. E20 showed no changes in formaldehyde emissions. Their observation followed same behaviors as other works. Previous studies also reported no or inconsistent changes in formaldehyde emissions as a function of ethanol content [171–174]. Acetone emission reductions were seen in both the 1996 Honda and the 2007 Chevy Silverado. The 1996 Honda showed reductions

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

1469

Fig. 32. (a) and (b) Individual carbonyl compound emissions for the 96 Honda Accord (a) and the 07 FFV Chevrolet Silverado (b) over FTP operation [166].

Fig. 33. (a) and (b) 1,3-Butadiene and BTEX emissions for the 96 Honda Accord (a) and the FFV Chevrolet Silverado (b) over FTP operation [166].

in acetone emissions of 39–56%, with higher ethanol levels related to the greater reductions. For the 2007 Chevrolet Silverado, the highest acetone reductions were achieved with E10, with reductions of 63% (compared to CARB 2) and 60% (compared to CARB 3). Higher molecular weight carbonyls were found at fairly low levels for the 1996 Honda Accord and none of the emission changes were statistically significant. Ethanol blended fuels all had higher crotonaldehyde emissions than CARB 2 for the 1996 Honda, as well. In fact, the use of CARB 3, E10, and E20 resulted in increases in crotonaldehyde emissions of 486%, 510%, and 327%, when compared to CARB 2. Fig. 32(a) and (b) represents the individual carbonyl compound emissions for the 96 Honda Accord (a) and the 07 FFV Chevrolet Silverado (b) over FTP operation. Fig. 33(a) and (b) represents the BTEX and 1,3-butadiene emissions over the FTP for the 1996 Honda Accord (a) and 2007 Chevrolet Silverado (b). The author noted that ethylbenzene was almost undetectable for all fuels and both vehicles. For the 1996 Honda Accord, BTLX and 1,3-butadiene emissions were significantly higher for CARB 2 than the other fuels. They noted a previous study [172], which had shown that benzene decreased with increasing ethanol levels, the current study showed that E20 had lower benzene, as well as toluene and xylene emissions than either CARB 3 or E10. Their results presented that benzene levels for the 2007 Chevrolet Silverado did not show consistent trend benzene levels were undetectable for E85 and were lower for CARB 3 and E50 (compared to CARB 2), while benzene levels for E10 and E20 were similar to those of CARB 2. The lower emissions of BTEX species for the E20 blend might be due to lower levels of total aromatics in the fuel. The benzene emissions also followed a trend that was roughly consistent with the benzene level in the fuel. Benzene was formed from either unburned fuel-borne benzene or benzene

formed during combustion of other aromatic and non-aromatic compounds found in gasoline [178]. The authors compared their observation with other works. Previous studies had shown that benzene generally decreased with increasing levels of ethanol, with this trend primarily be attributable to benzene levels in the fuel [164,172–174,179,180]. The higher BTEX emissions for CARB 2 did not appear to be directly attributable to fuel aromatic levels or oxygen content. Although the CARB 2 fuel had the highest levels of benzene, ethylbenzene and m/p xylenes, the CARB 3 and E10 fuels had either higher or comparable levels of toluene, o-xylene and total aromatics. Similar conclusions about fuel aromatic levels cannot be drawn about 1,3-butadiene (which is characterized as a human carcinogen and as precursor for secondary formation of formaldehyde and acrolein), because it is a product of fuel fragmentation and is not presented originally in the fuel [181,182]. Their observation followed same behaviors as other works. Previous studies had not shown consistent trends for 1,3-butadiene, either [171,172,174,176]. In their study, the 2007 FFV Chevrolet Silverado, showed a consistent decreasing trend in 1,3-butadiene, with emissions decreasing as ethanol level increased. Emissions of 1,3butadiene were undetectable for E85 and E50 showed a reduction of 78% compared to CARB 2. Benzene levels for the 2007 Chevrolet Silverado did not show consistent trends with increasing ethanol levels. Benzene levels were undetectable for E85 and were lower for CARB 3 and E50 compared to CARB 2, while benzene levels for E10 and E20 were similar to those for CARB 2. They mentioned the latter phenomenon might be due to the fact that the addition of oxygenated compounds such as ethanol inhibits the oxidation of benzene. It was therefore possible that an increase in soot volume fraction might result in some increases for benzene emissions [183].

1470

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

For other BTEX compounds, toluene, and m-, p- and o-xylene, the highest emissions were found for CARB 2, while E20 and E50 showed higher emissions of these species than the other ethanol blends, i.e., CARB 3, E10 and E85. The substantially lower BTEX emissions for E85 relative to the other blends was presumably due to the higher oxygen content and the lower amount of aromatic compounds in the fuel, although the other fuels did not generally follow this trend. For both the 1996 Honda and the 2007 Chevy, emissions of BTEX and 1,3-butadiene were mostly produced during the cold-start of FTP, while their concentration levels during the second and third hot-start phases were negligible. 5.4.4. Summary The study of regulated and unregulated emissions profiles of gasoline-powered light-duty vehicles included models ranging in years from 1984 to 2007. Test fuels included a CARB phase 2 certification fuel with an 11% MTBE content, a CARB phase 3 certification fuel with a 5.7% ethanol content, E10, E20, E50, and E85. Regulated and unregulated emission and fuel consumption measurements were analyzed over the FTP using a chassis dynamometer in at least duplicate for each vehicle/fuel test combination. The results of unregulated emissions lead to the following conclusions:

 In general, carbonyl emissions were lower for the ethanol       





blends than those of CARB 2 and CARB 3 fuels, with the exception of the E85 fuel. Carbonyl emission levels were higher for the 1996 Honda Accord than those of the 2007 FFV Chevrolet Silverado. The most consistent trend for carbonyl emissions was an increase in acetaldehyde emissions with increasing ethanol. Using of E85 resulted in significantly higher formaldehyde and acetaldehyde emissions than for the CARB fuels and the other ethanol blends. 1,3-butadiene and BTEX emissions were found in lower levels for the 2007 Chevrolet Silverado than the 1996 Honda Accord. In general, the addition of ethanol resulted in lower toxic emissions for the Honda Accord, compared to the CARB 2 fuel, with E20 having the lowest BTEX emissions. For the Chevrolet Silverado, 1,3-butadiene showed the most consistent trends, with CARB 2 having the highest emissions and emissions decreasing as a function of ethanol level. For toluene, and m-, p- and o-xylene, for the 2007 Chevrolet Silverado, the highest emissions were found for the CARB 2 fuel, while the E20 and E50 fuels interestingly showed higher emissions of these species than the other ethanol blends, i.e., CARB 3, E10, and E85. The unregulated emissions showed some trends with decreasing BTEX emissions with increasing ethanol for the 1996 Honda Accord and very low levels of toxic aromatics for the E85 fuel for the 2007 Chevrolet Silverado, but the BTEX emissions did not appear to be directly correlated to fuel aromatic levels, although the CARB 2 fuel did have the highest level of benzene, ethylbenzene, and p/m xylenes. Overall, the impact of ethanol on emissions for the in-use gasoline vehicle fleet can depend on a number of factors, including the mix of vehicle technologies and the ability of these vehicles to adjust to the level of ethanol in the fuel, the sensitivities of different vehicles to changes in ethanol content, interactions with other fuel properties, such as volatility, as well as other potential factors.

and gasoline were the main objective of Yang's work [184]. But, the emission characteristics of carbonyls are presented in this literature review study. 5.5.1. Test experimental setup and fuels Both unleaded gasoline (E0) and an unleaded blend with 3% ethanol (E3) were tested. Nine motorcycles manufactured by three companies in Taiwan with the most overall sales were tested in that study. All nine were four-stroke motorcycles. The fuel systems for the nine tested motorcycles were all carburetor systems since most motorcycles used carburetor, whether in Taiwan or other countries. The displacement volumes were from 100 cm3 to 150 cm3 and all were manufactured after 2005 with pre-testing mileages between 733 and 15,800 km. Since E3 was designed for using in vehicles needing not modification, the test motorcycles were not modified and all motorcycles had the same aftertreatment device—a two-way catalytic converter. The motorcycles were tested with E3 and E0 separately. Before each test, the fuel tank was drained and the vehicle run with test fuel for at least 1 h to avoid the shadow effect of the old residual fuel. In addition to these nine motorcycles, two brand-new motorcycles of the same manufacturer and model were durability tested with E3 and E0, respectively. The driving modes were comprised of idling, acceleration, cruise and deceleration to simulate real-world deterioration within a short period of time. The running mileage was about 500 km every day until they accumulated 15,000 km. Air-pollutant emissions were measured every 2500 km up to 15,000 km. The motorcycles were inspected and maintained fallowing the manufacturer's instructions. Air-pollutant emissions were measured at 5000 and 10,000 km both before and after maintenance. Fig. 34 illustrates the motorcycle emission sampling system. 5.5.2. Emissions testing and analysis After sample collection, they drew the diluted exhaust from the Tedlar bag into a pre-coated dinitro-phenyl-hydrazine (DNPH) cartridge (LpDNPH SIO Cartridge, Supelco Inc.) at a sampling rate of 1 L/min for 20 min. The cartridges were then capped and stored until analysis. Before analysis, each cartridge was extracted with 5 mL of acetonitrile. Then the extract was passed through a 0.45 1 m filter to remove particles during the extraction. Analysis was performed by a high-performance liquid chromatography/ultraviolet detector (HPLC/UV, Hitachi L-2400). Extracts were analyzed with a 250 mm (length) 4.6 mm (diameter) Mightysil RP-18 GP column at a flow rate of 1 mL/min and detected at a wavelength of 360 nm. The gradient elution program was applied, beginning with a mixture of mobile-phase, methanol/water/acetonitrile

5.5. H.H. Yang and co-workers (2012) The emission characteristics of regulated air pollutants and carbonyls from motorcycles using gasoline blended with ethanol

Fig. 34. Illustration of the motorcycle emission sampling system [184].

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

(0/80/20) for the first 5 min; then methanol/water/acetonitrile (30/20/50) for 35 min. The total run time was 40 min. Fifteen carbonyls were analyzed in their study: formaldehyde, acetaldehyde, acrolein, acetone, propionaldehyde, crotonaldehyde, butyraldehyde, benzaldehyde, isovaleraldehyde, valeraldehyde, m-tolualdehyde, o-tolualdehyde, p-tolualdehyde, hexaldehyde and 2,5-dimethylbenzaldehyde. A commercial aldehyde-DNPH standard (TO-11 Mix, Supelco Inc.) was used for calibration and neat aldehydes (Sigma-Aldrich Inc.) were used for recovery tests. Medium blanks were measured, and the blank values were subtracted from samples. Ranges of recovery, reproducibility (in terms of coefficient of variation), linearity (in terms of R-square of the regression line) and method of detection limit (in terms of emission factors) were 77.1–98.2%, 3.28–6.47%, 0.990–0.998 and 0.002– 0.031 1 g/km, respectively. 5.5.3. Results and discussion The carbonyl emission factors for the nine test motorcycles are listed in Table 23. The authors recorded that there was no significant difference for the carbonyl emission profiles between the two fuels. Acetaldehyde, formaldehyde, acetone and benzaldehyde were the major compounds, which account for 28.1%, 18.2%, 10.9%, 8.49% for E0 and 31.9%, 31.9%, 8.97%, 8.15% for E3 of the 15 carbonyls, respectively. Total carbonyl (15 carbonyls) emission factors were 1289 7502 lg/km and 1579 7368 lg/km for E0 and E3, respectively. Using E3 as fuel resulted in a 22.5% increase of total carbonyl emissions, but it was not statistically significant (pvalue ¼ 0.137). For individual compounds, using E3 increased the emission of most carbonyls. Acetaldehyde, formaldehyde, propionaldehyde and benzaldehyde were increased by 40.9%, 37.0%, 20.2% and 19.1%, respectively. However, they observed that only the increase of acetaldehyde was statistically significant (pvalue ¼ 0.014). Carbonyls were formed primarily from the reaction of hydrocarbons with OH radicals. Combustion of ethanol tended to form carbonyl compounds due to its hydroxyl structure. In addition, the combustion of ethanol with two carbons in structure could easily form acetaldehyde which contains two carbons as well. Their observation followed same behaviors as other works. A study by Pang also showed that the addition of ethanol in gasoline resulted in higher emission of acetaldehyde [185]. In addition, the higher emission of carbonyls attributed to the addition of rich oxygen-containing ethanol [172, 186].

1471

5.5.4. Summary That study investigated the emissions of CO, THC, NOX, CO2 and carbonyls for motorcycles using E0 and E3 gasoline/ethanol blended fuels. Nine motorcycles manufactured by three companies in Taiwan with the most overall sales were tested. All nine were fourstroke motorcycles. The main summaries of the paper are the following.

 The emission factors of 15 carbonyls were 1289 and 1600 lg/km for E0 and E3, respectively.

 The emission of acetaldehyde was significantly increased with using E3 as fuel.

 For individual compounds, using E3 increased the emission of most carbonyls.

 Acetaldehyde, formaldehyde, propionaldehyde and benzaldehyde were increased with using ethanol. 5.6. H. Zhao and co-workers (2011) Regulated and unregulated emissions from four passenger cars fueled with different methanol/gasoline blends were investigated over the NEDC cycle in a study [187]. However, the influence of different methanol/gasoline blends on unregulated emissions is only mentioned in the present literature review study. 5.6.1. Test experimental setup and fuels Four passenger cars were tested in 13 configurations. Commercial 93# gasoline was used as the base fuel. Industrial grade methanol was mixed in fractions of 15%, 20%, 30%, 50%, 85% and 100% by volume, and the fuel blends were named M15, M20, M30, M50, M85 and M100. Vehicle 1 (mileage: 1000 km), vehicle 3 (mileage: 1000 km) and vehicle 4 (mileage: 22,751 km) were each powered by 1.8 L gasoline engines and were tested in three configurations: (1) fueled with baseline gasoline and using the original equipment manufacturer (OEM)-installed TWC; (2) fueled respectively with Ml5, M85 and Ml00 and using the OEM-installed TWC; (3) fueled respectively with Ml5, M85 and Ml00 and retrofitted with a new TWC which was designed specifically only for each vehicle with a main aim to reduce formaldehyde emissions. Vehicle 2 (mileage: 105,000 km) was powered by a 1.6-L gasoline engine and was only tested with different fuels namely, gasoline, M20, M30 and M50 with the OEM-installed TWC. The emission testing was performed on a chassis dynamometer. The drive cycle used was the New European Driving Cycle (NEDC), which included four ECE (urban cycle) and one EUDC

Table 23 Carbonyl emission factors for E0 and E3 (mean7 SD, l g/km, n¼ 9) [184]. Carbonyls

E0

E3

Reduction (%)a

p-Value of paired-sample t-test

Formaldehyde Acetaldehyde Acrolein Acetone Propionaldehyde Crotonaldehyde Butyraldehyde Benzaldehyde Isovaleraldehyde Valeral dehyde m-Tolualdehyde o-Tolualdehyde p-Tolualdehyde Hexaldehyde 2.5-D imethylbenzaldehyde 15 Carbonyls

2357 108 362 7 155 91.9 7 46.3 1417 114 67.6 7 37.1 26.0 7 16.6 53.6 7 32.5 1097 81.5 28.17 19.3 38.8 7 31.4 35.87 15.4 50.6 7 33.0 17.4 7 17.0 15.4 7 9.71 16.0 7 10.8 1289 7 502

322 7 129 510 7 178 90.6 ¼ 56.9 1437 85.2 81.3 7 46.0 28.4 7 16.1 53.4 7 25.3 1307 63.2 30.8 ¼ 14.8 44.17 26.9 39.8 7 15.1 54.0 7 27.7 30.0 7 26.3 14.3 79.18 17.7 7 4.4 15797 368

37.0 40.9 1.42 2.06 20.2 9.27 0.46 19.1 9.71 13.7 11.2 6.57 3.98 7.16 10.8 22.5

0.179 0.014 0.946 0.871 0.320 0.543 0.987 0.189 0.705 0.614 0.408 0.728 0.127 0.704 0.229 0.137

a

Reduction percentage (%) ¼(E0
E3)/E0*100 (%).

1472

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

(extra-urban cycle). The whole tests cycle lasted for 1180 sec. Before testing, all cars were conditioned at a temperature of (25 72 °C) over 16 h. The measurements were carried out twice at the same conditions, and all results were averaged over the two measurements. 5.6.2. Emissions testing and analysis The standard mixture of VOCs (SEPA, China) contains benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, styrene, nbutylacetate and n-undecane. Fig. 35 shows a schematic diagram of authors’ measurement system for vehicle exhaust emissions. VOCs from the CVS-diluted exhaust were collected through a battery-operated air pump at a flow rate of 750 mL/min using a Tenax TA sorbent tube. Tenax samples were analyzed by the thermal desorption pre-concentration method, followed by identification by high resolution gas chromatography with a mass spectrometer detector (GC–MS). Carbonyl compounds in the dilution tunnel were sampled through a battery-operated air pump at a flow rate of 1200 mL/ min using a 2,4-dinitrophenylhydrazine DNPH)-coated silica cartridge, standard technique. They also pointed out the standard mixture contains 14 components, namely, formaldehyde, acetaldehyde, acrolein, acetone, propionaldehyde, crotonaldehyde, methyl ethyl ketone, methacrolein, butyraldehyde, benzaldehyde, valeraldehyde, tolualdehyde, cyclohexanone and hexanaldehyde. 5.6.3. Results and discussion The authors summarized the average VOC emission factors for vehicles fueled with methanol/gasoline blends at different mixing ratios. BTEX (benzene, toluene, ethylbenzene, p/m and o-xylene) is shown for about 95% of total VOCs in Table 24. For all

Fig. 35. Schematic diagram of measurement system for vehicle exhaust emissions [187].

methanol/gasoline blends, total VOCs and BTEX emissions were decreased as compared with baseline vehicle fueled only with gasoline. For BTEX emissions, M85 showed the highest decrease (97.4%) while M15 showed the lowest decrease (19.7%) compared with the baseline. Toluene dominated BTEX and total VOC emissions for all methanol/gasoline blends, accounting for approximately 40–50% of all VOCs. Unsaturated hydrocarbons in the fuel were precursors responsible for the formation of aromatic species. Since methanol was free of unsaturated hydrocarbons, it had the effect of reducing the aromatic precursors, leading to a reduction of aromatics. Xylene emissions were related to the aromatic content of the fuel. Aromatics were not present in methanol; hence xylene emissions were reduced when the cars were fueled with methanol/gasoline blends. Carbonyl compound emission factors from vehicles fueled with methanol/gasoline blends at different mixing ratios are presented in Table 25. Formaldehyde emissions were the most abundant carbonyl for all ethanol/gasoline blends followed by acetaldehyde, acrolein þacetone, benzaldehyde, and propionaldehyde. They reported that, formaldehyde could be produced from alcohols and paraffin, but the generation of formaldehyde from methanol oxidation was easier than from hydrocarbons, which results in higher formaldehyde emissions from engines fueled with methanol/ gasoline blends as compared with baseline gasoline-fueled engines. With the increase in methanol content, the formaldehyde concentrations also increased. The authors compared their results with previous studies which done by Zervas et al. [167] and Wei et al. [188]. Wei et al. [188] found that formaldehyde emission characteristics were approximately linear to the amount of cyclic-supplied fuel methanol. In their study, with low-tomiddle ratio methanol/gasoline blends (M15, M20, M30 and M50), formaldehyde emissions had a slight increase compared with the baseline, while that of high ratio blends (M85 and M100) were three times higher than the baseline. However, there was a decrease in acetaldehyde emissions of 13–65% with different ratios of methanol/gasoline blends. In the case of other carbonyls, there was an increase or decrease more or less. The sharp increase in formaldehyde emissions eventually resulted in the increase of total carbonyls with the exception of M20, which showed no obvious change from the baseline. Although M20, M30 and M50 were all tested on Vehicle 2, the category and quantity of additives of the three fuels were different, which resulted in the total carbonyls emitted from M50 being slightly higher than that from M20 but significantly lower than that from M30. 5.6.4. Summary Regulated and unregulated emissions from four passenger cars fueled with different methanol/gasoline blends (M15, M20, M30, M50, M85 and M100) were investigated over the NEDC cycle. Commercial 93# gasoline was used as the base fuel. Emissions of eight VOCs and 13 carbonyl compounds were identified and

Table 24 VOCs emission factors for different mixing ratios of methanol/gasoline fueled vehicles (mg/km) [187]. Vehicle 1

Benzene Toluene n-Butylacetate Ethyl benzene p,m-Xylene Sturene o-Xylene n-Undecane Total VOCs

Vehicle 2

Vehicle 3

Vehicle 4

Gasoline

M15

Gasoline

M20

M30

M50

Gasoline

M85

Gasoline

Ml 00

0.434 1.559 0.021 0.335 0.481 0.089 0.380 0.028 3.327

0.497 1.231 0.018 0.217 0.342 0.037 0.274 0.015 2.631

1.658 7.594 0.010 2.396 2.429 0.352 1.951 0.099 16.489

1.030 4.338 0.010 0.943 1.088 0.271 0.866 0.047 8.593

1.208 4.963 0.037 0.803 0.952 0.130 0.755 0.035 8.883

1.060 2.375 0.034 0.319 0.448 0.099 0.394 0.010 4.739

2.415 4.957 0.034 1.313 1.755 0.401 1.621 0.016 12.512

0.032 0.152 0.014 0.026 0.059 0.013 0.044 0.008 0.348

0.848 1.875 0.021 0.402 0.577 0.116 0.439 0.037 4.315

0.202 0.588 0.015 0.110 0.160 0.020 0.129 0.009 1.233

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

1473

Table 25 Carbonyl compound emission factors for different mixing ratios of methanol/gasoline fueled vehicles (mg/km) [187]. Vehicle 1

Formaldehyde Acetaldehyde Acrolein þ Acetone Propionaldehyde Crotonaldehyde Methyl ethyl ketone Methacrolein Butyraldehyde Benzaldehyde Valeraldehyde Tolualdehyde Cyclohexanone Hexanaldehyde Total carbonyls

Vehicle 2

Vehicle 3

Gasoline

MI5

Gasoline

M20

M30

M50

Gasoline

M85

Gasoline

M100

1.496 0.386 0.241 0.076 0 0.216 0 0 0.133 0.015 0 0 0 2.563

1.878 0.317 0.263 0.076 0.016 0 0.159 0 0.138 0.020 0 0 0.080 2.948

2.918 2.628 0.821 0.399 0.049 0 0.303 0.498 0.181 0.103 0 0 0 7.900

3.270 2.148 0.614 0.266 0 0 0.281 0.480 0 0.053 0 0 0 7.112

5.045 2.291 0.684 0.247 0 0.507 0.150 0 0.105 0 0 0 0 9.029

5.182 1.504 0.541 0.210 0 0 0.439 0 0.080 0 0 0 0 7.956

2.140 1.319 0.696 0.212 0.085 0.347 0 0.074 0.565 0.044 0 0 0 5.482

5.956 0.954 0.460 0.207 0.075 0.264 0 0.032 0.332 0 0 0 0 8.281

1.784 0.761 0.474 0.141 0.052 0.123 0.039 0 0.258 0 0 0 0 3.630

5.348 0.268 0.181 0.076 0 0.068 0 0.020 0.121 0 0 0 0.080 6.162

quantified. The effects of different mixing ratios and new TWCs on emissions of regulated and unregulated VOC and carbonyl compounds were studied. The conclusions drawn from that study are the following points:

 For all methanol/gasoline blends, total VOCs and BTEX decreased relative to the baseline.

 For BTEX emissions, as compared with the baseline, M85 had 



Vehicle 4

the highest decrease (97.4%) while M15 had the lowest decrease (19.7%). With low-to-middle ratio methanol/gasoline blends (M15, M20, M30 and M50) formaldehyde emissions had a slight increase; while that of high ratio blends (M85 and M100) were three times compared with gasoline counterparts. Total carbonyl emissions increased with increasing percentage of methanol irrespective vehicle 2, M20.

Table 26 Engine specifications [189]. Model

Isuzu 4HF1

Type Maximum power Maximum torque Bore/stroke Displacement Compression ratio Injection pump type Injection nozzle

Water-cooled, in-line, four-cylinder, DI engine 88 kW/3200 rev/min 285 N m/1800 rev/min 112 mm/110 mm 4334/cm3 19.0:1 Bosh in-line type 5-hole nozzle

5.7. Z.H. Zhang and co-workers (2010) In Zhang's study et al. [189] the effect of the new combustion scheme, coupled with the effect of a DOC, on regulated and unregulated emissions, particulate number concentration and size distribution was investigated based on the Japanese 13 Mode test cycle with methanol. But, the effect of methanol on unregulated emissions is mentioned in this literature review study. 5.7.1. Test experimental setup and fuels The test engine was a 4-cylinder natural-aspirated directinjection diesel engine with specifications shown in Table 26. The engine had been modified for the new combustion scheme. The modification included the installation of a methanol injection and control system to the air intake manifold of the diesel engine with one fuel injector for each cylinder. The modification also included a separate fuel tank and fuel pump for the methanol. The experimental setup is shown in Fig. 36. The engine was coupled with an eddy-current dynamometer and the engine speed and torque were controlled by the Ono Sokki diesel engine test system. A commercial Engelhard CCX8772 A DOC was installed at the down-stream end, 850 mm from the exhaust manifold. The used fuels included Euro V diesel fuel with less than 10-ppm by weight of sulfur and industrial grade methanol. 5.7.2. Emissions testing and analysis Unregulated gas emissions including methane, ethyne, ethene, 1,3-butadiene, BTX, formaldehyde and unburned methanol were online analyzed with an Air-Sense multi-components gas analyzer (V&F Airsense Net). The analyzer was an Ion Molecule Reaction

Fig. 36. Schematic diagram of experimental system [189].

(IMR) mass spectrometer, which allowed dynamic studies of gaseous emission in low concentration. The gas sample was taken directly from the exhaust pipe and maintained at 190 °C to the multi-component gas analyzer. In their experimental investigation, benzene, toluene, and formaldehyde and methanol were calibrated directly using standard gases, while the other

1474

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

compounds were calibrated through an indirect way based on information provided by the equipment supplier. The test modes in the Japanese 13 Mode test cycle for diesel vehicles were adopted to evaluate the effect of the DMCC and the DOC on regulated and unregulated emissions. The detailed operating conditions of each mode and the methanol fumigation strategy used are shown in Table 27. The emissions were weighted over the Japanese 13 Mode test cycle using a set of weighting factors. In authors’ study, fumigation methanol was applied only at medium to high engine loads when the exhaust gas temperature is high enough to ensure proper DOC operation. Thus in their study, fumigation methanol was applied in mode 6 to mode 12 only. Moreover, mode 9 was selected to analysis the SOF in the particulate while mode 9 and mode 11 were chosen to investigate the particulate number concentration and size distribution. 5.7.3. Results and discussion Methanol and formaldehydes are the two major unregulated emissions associated with the combustion of methanol [189]. As shown in Fig. 37, there is a sharp increase in methanol emission when the engine was operated in the DMCC mode. For the baseline engine, the weighted brake specific methanol emission was only 0.03 g/kWh, however it increased to 0.52 g/kWh, 0.68 g/kWh and 0.86 g/kWh respectively at fumigation methanol level of 10%, Table 27 The Japanese 13 Mode test and methanol fumigation strategy [189]. Mode No. Speed (rev/ min)

Torque (%) Weight factor

Exhaust temp.a (°C)

Methanol fumigation

1 2 3 4 5 6 7 8 9 10 11 12 13

0 20 40 0 20 40 40 60 60 80 95 80 5

95 158 217 95 212 282 341 481 360 452 532 507 188






þ þ þ þ þ þ þ


a

Idle 1280 1280 idle 1920 1920 2560 2560 1920 1920 1920 2560 1920

0.205 0.037 0.027 0.205 0.029 0.064 0.041 0.032 0.077 0.055 0.049 0.037 0.142

Exhaust gas temperature of baseline engine.

Fig. 37. Effect of DMCC and DOC on unburned methanol and formaldehyde emissions [189].

20% and 30%. After passing through the DOC, there was still about 0.028 g/kWh of methanol emission under different levels of fumigation methanol. The results indicated that high methanol emission occurred with fumigation methanol. They reported that, methanol in the engine exhaust was either the intermediate product from the combustion of diesel fuel or the fumigation methanol which had not been burned. For diesel only operation, in the absence of fumigation methanol, the only source of methanol was the intermediate combustion products of the diesel fuel. The very low concentration of methanol in the diesel fuel operation indicated that the intermediate products only had a small contribution to the methanol in the engine exhaust. When operating in the fumigation mode, the significantly higher methanol emission was mainly due to the quenched and trapped methanol which could not be oxidized in the expansion stroke of the combustion cycle. High formaldehyde emission was also found in the DMCC mode, as shown in Fig. 37. Compared with the baseline engine, there was an increase of 17%, 30% and 47% formaldehyde emissions, respectively, for 10%, 20% and 30% fumigation methanol. They found that formaldehyde was an intermediate combustion product. The increase of fumigation methanol led to a reduction in combustion temperature which might enhance the formation of the intermediate combustion product and hence an increase of formaldehyde. The authors compared their results with previous studies. They indicated that, previous work of Rideout et al. [36], Sakamoto et al. [190], Kim [191] and Lipari [192] showed that methanol fueled engines had a tendency to emit significant amount of formaldehyde. In addition, Chao et al. [193] also found a high formaldehyde emission from a diesel engine fueled with diesel blended with up to 15% by volume of methanol. Formaldehyde was an important secondary pollutant and played an important role in urban smog chemistry. Thus the high formaldehyde emission was a disadvantage of DMCC operation. Among the various compounds in the exhaust emissions, the effect of DMCC on methane (CH4), ethyne (C2H2), ethene (C2H4), 1,3-butadiene (C4H6), benzene (C6H6), toluene (C7H8) and xylene (C8H10) was investigated in their experiment work based on the Japanese 13 Mode test cycle. The weighted brake specific emissions, together with the standard errors at 95% confidence level, are shown in Table 28. Table 28 shows that, compared with the baseline engine, methane increased, while ethyne and ethene decreased, with fumigation methanol. With increasing level of fumigation methanol, the combustion temperature decreased. However, ethyne and ethene were the products of thermal pyrolysis of diesel fuel and methanol. Probably the combustion of diesel fuel in fumigation methanol improved the diffusion combustion, leading to the reduction of both ethyne and ethene. 1,3-butadiene is an air toxic commonly found in the exhaust gas of diesel and petrol vehicles. The results showed a significant reduction of the compound when the engine was operated in the DMCC mode. Their results were in agreement with Takada et al. [194] who suggested that 1,3-butadiene was emitted easily under high exhaust gas temperature condition. Probably the high heat of evaporation of methanol and thus low combustion temperature could lead to the reduction of 1,3-butadiene. Benzene, toluene and xylene (BTX) are air toxics emitted from many sources, including motor vehicles. Benzene and toluene emissions were higher in the DMCC mode. The increase in benzene emissions were 20.4%, 19.1% and 14.1% respectively at 10%, 20% and 30% fumigation methanol; while the corresponding increase in toluene emissions were 38.9%, 96.8% and 69.0%. However there was no significant difference in xylene emissions. Overall speaking, there was an increase in BTX emissions with fumigation methanol. The increase in BTX emissions were 25.4%, 48.6% and 35.6% respectively at 10%, 20% and 30% fumigation

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

1475

Table 28 Hydrocarbon speciation with and without fumigation methanol (weighted brake specific emissions based on Japanese 13 Mode test cycle) [189]. lg/kWh

Methane (CH4)

Ethyne (C2H2)

Ethene (C2H4)

1,3-butadiene (C4H6)

Benzene (C6H6)

Toluene (C7H8)

Xylene (C8H10)

BTX

M0 M10 M20 M30

48 7 2 567 3 627 2 707 2

42017 180 3209 7 128 3042 7 116 2903 7 107

20667 48 928 7 23 880 7 18 849 7 12

3955 7 182 23077 140 2168 7 166 22717 173

161 711 194 714 193 716 184 712

1267 7 1757 9 248 7 15 2137 11

22 7 2 207 1 21 7 2 187 1

310 712 389 714 461 711 421 713

methanol. The authors compared their observation with other work. Tang et al. [6] found a high BTEX emission from a diesel engine fueled with diesel–ethanol blends, and they attributed the high BTEX emission to the increase in air/fuel ratio due to the addition of ethanol as an oxygenate. According to their report, methanol had high oxygen content and could also increase the air/fuel ratio, and thus leading to higher BTX emissions when the engine was operated in the DMCC mode. The DOC was found to be effective also in reducing these emissions. The percentage reduction in the Japanese 13 Mode weighted brake specific emissions of them varies from 45% to 68%. Thus the DOC was also effective in reducing the air toxics, including 1,3-butadiene and the BTX. The author selected the Mode 9 to investigate the effects of fumigation methanol and the DOC on SOF on diesel particulate, for diesel fuel and for 10% and 30% fumigation methanol. The SOF in the particles were attributed to unburned, pyrolyzed or partially oxidized fuel and lubricating oil and were transferred from the gas phase to the particulate phase when the exhaust cooled [195]. With fumigation methanol, higher unburned hydrocarbon, including unburned methanol and formaldehyde, might tend to increase the SOF in the PM. As shown in Fig. 38, the SOF in the PM increased with the level of fumigation methanol. The SOF in the particulate was 65% in the baseline engine, which increased to 71% and 80% respectively at 10% and 30% fumigation methanol. Their observation followed same behaviors as others work. Lin [196] also found increase of SOF when the engine was operated with diesel– methanol blends at different operating conditions. Due to oxidation of the SOF, the percentage of SOF in the particulate with DOC was about 25–29% less than that without DOC. Thus, the percentage of SOF in the PM was only 6.8% higher at 10% fumigation and 12.1% higher at 30% fumigation compared with that of the baseline engine. 5.7.4. Summary Experiments were conducted on a 4-cylinder direct-injection diesel engine operating on the DMCC scheme. The effect of the new combustion scheme, coupled with the effect of a DOC, on regulated and unregulated emissions was investigated based on the Japanese 13 Mode test cycle. The Euro V diesel fuel with less than 10-ppm by weight of sulfur and industrial grade methanol were used. The following conclusions are summarized from that work:

 Sharp increase in unburned methanol emission when the engine was operated in the DMCC mode.

 High formaldehyde emission was also found in the DMCC mode.  Compared with the baseline engine, methane increased, while ethyne and ethene decreased, with fumigation methanol.

 A significant reduction of 1,3-butadiene was found when the engine was operated in the DMCC mode.

 Benzene and toluene emissions were higher in the DMCC mode; 

however there was no significant difference in xylene emissions. Overall, there was an increase in BTX and SOF emissions with fumigation methanol.

Fig. 38. Effect of DMCC and DOC on proportion of SOF in the particulate at mode 8 [189].

5.8. Z.H. Zhang and co-workers (2010) Zhang's work et al. [142] aimed to provide further experimental data on the effect of fumigation methanol on the emissions of a diesel engine and the sensitivity of these emissions to the amount of fumigation methanol applied under different operating conditions. Besides the regulated emissions, certain unregulated emissions were also measured. But, the effect of methanol fumigation on unregulated emissions is only chosen in present literature survey work. 5.8.1. Test experimental setup and fuels Their experimental system and Engine specifications are shown in Fig. 36 and Table 26, respectively. The Euro V diesel fuel and industrial grade methanol were used. 5.8.2. Emissions testing and analysis In their research unregulated gases including benzene, toluene, formaldehyde and methanol were online analyzed with the Air sense multi-component gas analyzer. The gas sample was taken directly from the engine exhaust and maintained at 190 °C to the multi-component gas analyzer. In that study, benzene, toluene, formaldehyde and methanol were calibrated directly using standard gases, while other compounds were calibrated indirectly based on information provided by the equipment supplier. Experiments were carried out at various steady state operating conditions. All the gas concentrations were continuously measured for 5 min at the exhaust tailpipe of the diesel engine. Three tests were carried out for each operating condition and the results were found to agree with each other within the 95% confidence level. They conducted the experiment operating the engine at speed of 1920 rev min
1, and at engine loads of 46, 92, 138, 184 and 218 N m, corresponding to brake mean effective pressures of 0.13, 0.27 0.40, 0.53 and 0.63 MPa, respectively. Experiments were

1476

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Fig. 39. Effect of fumigation methanol on unburned methanol emission [142].

firstly carried out with diesel fuel alone to build up a database for comparison with those obtained with fumigation methanol. Experiments were then carried out with the diesel fuel taking up 90% of the desired engine load while the rest of the desired load was taken up by fumigation methanol. Experiments were repeated with the diesel fuel taking up 80% and 70% of the desired engine loads, with fumigation methanol providing respectively 20% and 30% of the desired engine loads. 5.8.3. Results and discussion The brake specific unburned methanol emission in the exhaust gas is shown in Fig. 39. The unburned methanol emission was no more than 0.1 g kW
1 h
1 for the baseline engine but significantly increased with fumigation methanol, especially at low engine load. At the engine load of 0.13 MPa, it increased to and 25.3 g kW
1 h
1 14.4 g kW
1 h
1, 18.5 g kW
1 h
1 respectively, for 10%, 20% and 30% fumigation methanol. At higher engine loads, the unburned methanol emissions for fumigation methanol operation decreased rapidly but are still higher than that for diesel fuel. They wrote that the possible reason was that with increase of engine load, there was an increase in fuel burned and hence combustion temperature. The increase in the amount of methanol in the fuel would cause an increase of unburned methanol but the increase in combustion temperature tended to reduce the unburned methanol. Their results vividly illustrated that similar to the brake specific unburned methanol emission, the brake specific formaldehyde emission increased with increase of fumigation methanol and decreased with increase in engine load, as shown in Fig. 40. Compared with the baseline engine, there were about 1.8–2.2 times, 2.4–2.9 times and 3.4–4.5 times increase in formaldehyde emission for different engine loads, for 10%, 20% and 30% fumigation methanol respectively. They compared their observation with Chao et al. [193] who studied the effect of methanol on the emissions of carbonyl compounds generated from the diesel engine operating on diesel/methanol blends. Chao found that the formaldehyde emissions increased with the methanol fraction, which matched with the results of their study. Their results followed same behaviors as other works. Zervas et al. [167] found that the formaldehyde emissions increased with the methanol fraction, and suggested that exhaust formaldehyde was mainly produced from methanol. Zervas had similar variation in formaldehyde emission with percentage of methanol and engine load. The formation of formaldehyde from hydrocarbons and their

Fig. 40. Effect of fumigation methanol on formaldehyde emission [142].

further oxidation depend on the species in the combustion chamber, the temperature and the time spent under these conditions [197]. They reported that the increase of fumigation methanol leads to a reduction in combustion temperature which might enhance the formation of the intermediate combustion product and hence an increase of formaldehyde. Besides methanol and formaldehyde, the authors also measured the concentrations of the following hydrocarbons: ethyne, ethene, 1,3-butadiene, benzene, toluene and xylene, because most of them had high reactivity and toxicity. Their results are shown in Table 29. Ethyne (C2H2) and ethene (C2H4) emissions significantly decreased when fumigation methanol was applied. The average reduction of ethyne and ethene with different engine loads were respectively 78% and 54% for 10% fumigation methanol; while the corresponding reductions were 82% and 60% for 30% fumigation methanol. The authors compared their observation with other works. Flynn et al. [198] developed a chemical kinetic and mixing model to study the premixed, rich ignition process, using n-heptane, as a representative diesel fuel, blended with methanol. Flynn results also showed that methanol addition could reduce the concentrations of ethyne and ethene. As explained in Flynn et al. [198], methanol does not contain any C–C bonds and cannot then produce significant levels of these species. Ethyne and ethene were the products of thermal pyrolysis of diesel fuel and methanol. Probably the combustion of diesel fuel in fumigation methanol improved the diffusion combustion, leading to the reduction of both ethyne and ethene. For each engine load, there was a significant reduction of the compound when the engine was operated with fumigation methanol while the reduction was not directly related to the level of fumigation methanol. In fact, the reduction was about 57–69% with different engine loads and different levels of fumigation methanol. The authors’ observation followed same behaviors as other works. Takada et al. [194] suggested that 1,3-butadiene was emitted easily under high exhaust gas temperature condition. The cooling effect of methanol, associated with the high latent heat of evaporation, could lead to the reduction of 1,3-butadiene. Flynn et al. [198] found that addition of methanol reduced 1,3-butadiene emission and they attributed this to the same reasons leading to the reduction of ethyne and ethene emissions. Merritt et al. [199] recorded 24–82% reduction of 1,3-butadiene emission after the addition of different percentage of ethanol in the diesel fuel, while the reduction was not directly related to the percentage of ethanol

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

1477

Table 29 Hydrocarbon speciation with different levels of fumigation methanol [142]. Engine load (MPa)

% MeOH

C2H2 (lg m

0.13

M0 M10 M20 M30 M0 M10 M20 M30 M0 M10 M20 M30 M0 M10 M20 M30 M0 M10 M20 M30

197.5 86.9 71.5 62.4 270.7 121.2 93.6 76.4 250.6 106.1 90.7 84.8 187.5 82.2 85.8 76.7 141.7 79.6 85.5 90.5

0.27

0.40

0.53

0.63


3

)

C2H4 (lg m 175.3 34.2 33.3 30.2 195.7 48.7 32.8 30.8 173.6 38.4 31.9 30.2 133.0 28.8 29.1 26.9 185.9 40.6 40.9 37.2


3

)

C4H6 (lg m 555.7 206.3 207.9 205.7 600.5 257.6 214.4 204.7 536.2 191.7 185.8 184.1 466.0 141.5 143.6 146.9 533.2 206.8 217.1 212.2

in the fuel, which was in line with the results obtained in their investigation. The authors found that, the effect of fumigation methanol on the BTX emissions, as shown in Table 29, depended on both engine load and level of fumigation. There was a slight decrease or increase in the benzene emission with different levels of fumigation methanol and engine loads. They had used a number of studies for proving their obtained results. Takada et al. [194] suggested that benzene was easily oxidized at high temperature. When fumigation methanol was applied, the combustion temperature was reduced, which might lead to increase in benzene emission. However, it had been pointed out that the formation of mono and polynuclear aromatic compounds was related with the lack of oxygen to convert carbon atoms to carbon dioxide [200]. Thus with increase in fumigation methanol, the increase of oxygen content could improve combustion and promote the degradation of benzene and hence reduce benzene emission. Moreover, as explained in Inal [201], unsaturated hydrocarbons in the fuel were precursors responsible for the formation of aromatic and PAH species. Since fumigation methanol was free of unsaturated hydrocarbons, it had the effect of reducing the aromatics precursors, leading to the reduction of the aromatics. The above factors counteracted with each other, resulting in slight increase or decrease of benzene emission with different levels of fumigation methanol. Regarding toluene and xylene emissions, for each engine load, there was an increase in toluene emission but decrease in xylene emission when fumigation methanol was applied. Nelson et al. [202] found that benzene and toluene were largely formed in the combustion process from fuel fragments produced in the initial oxidative pyrolysis of the fuel. Thus, their formation was largely determined by combustion conditions such as local stoichiometry and temperature. However, xylene emission was related to the aromatic content of the fuel. The lower combustion temperature associated with the high latent heat of vaporization of methanol might lead to higher toluene emission. However, methanol was aromatic free and hence reduces xylene emission when the engine was operated with fumigation methanol. Overall speaking, there was an increase of the BTX emission with fumigation methanol, due mainly to the increase of toluene emission. 5.8.4. Summary Experiments were conducted on a 4-cylinder direct-injection diesel engine operating on Euro V diesel fuel and fumigation


3

)

C6H6 (lg m


3

22.7 23.9 27.7 26.1 28.8 36.7 32.8 30.2 35.5 33.1 30.2 22.4 29.8 27.1 31.3 27.1 33.5 30.7 37.8 36.4

)

C7H8 (lg m 12.8 26.7 63.3 56.5 13.3 35.1 30.9 52.1 11.6 25.7 52.3 44.5 13.1 21.6 39.8 31.5 16.3 212 40.1 30.7


3

)

C8H10 (lg m


3

)

5.9 2.5 2.3 3.2 6.0 2.9 2.1 1.8 5.0 2.2 2.3 1.7 5.3 2.1 1.8 1.3 6.1 2.5 2.3 1.4

BTX (lg m


3

)

41.4 58.1 102.3 85.6 48.2 74.7 65.8 84.2 50.1 61.0 85.7 68.5 48.2 50.8 72.9 59.9 55.9 54.0 80.2 68.5

methanol for 10%, 20% and 30% load displacement. The effect of fumigation methanol on engine performance, regulated and unregulated emissions were investigated. The following conclusions can be drawn from that study:

 Fumigation methanol decreased the emission of ethyne, ethene, 1,3-butadiene.

 Fumigation methanol significantly increased the emissions of unburned methanol, formaldehyde and the BTX. 5.9. C.S. Cheung and co-workers (2009) In Cheung's experiment et al. [203] the engine performance, regulated emissions and unregulated emissions were studied on a diesel engine fueled with Euro V diesel fuel, biodiesel, and three biodiesel–methanol blends. But, the unregulated emissions characteristics of methanol blends are only presented in current literature review study. 5.9.1. Test experimental setup and fuels Their experimental system and Engine specifications are shown in Fig. 36 and Table 26, respectively. The used fuels in that study included Euro V diesel fuel, biodiesel and biodiesel blended with methanol. Biodiesel used in their study was manufactured from waste cooking oil by Dunwell Petro-Chemical Ltd. The blended fuels were prepared by mixing 5%, 10% and 15% by volume of methanol in biodiesel and identified as BM5, BM10, and BM15. 5.9.2. Emissions testing and analysis Unregulated emissions included unburned methanol, formaldehyde, acetaldehyde, 1,3-butadiene, benzene, toluene and xylene, were measured with the Airsense multi-component gas analyzer. Standard benzene, toluene, methanol and formaldehyde gases were used to calibrate the Airsense multi-component gas analyzer while the other unregulated gases were calibrated indirectly with information provided by the equipment supplier. The tests were conducted at a steady engine speed of 1800 rev min
1, and at engine loads of 28 N m, 70 N m, 130 N m, 190 N m, and 240 N m, corresponding to the brake mean effective pressures of 0.08 MPa, 0.2 MPa, 0.38 MPa, 0.55 MPa, and 0.70 MPa, respectively. At each engine operating mode, experiments were carried out for the diesel fuel, biodiesel, BM5, BM10 and BM15. In order to ensure the repeatability of the measurements, the cooling

1478

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

water temperature was automatically controlled to 80 °C, and held to within 72 °C, while the oil temperature was maintained at 90– 100 °C, depending on the engine load. Before recording the data, the engine was allowed to operate for a few minutes until the engine reached a steady state, as reflected by the lubricating oil temperature and the cooling water temperature. Also, the diesel engine used in the experiment was not modified during all the tests. 5.9.3. Results and discussion Aldehydes emitted from internal combustion engines are intermediate products of hydrocarbons or oxygenated compounds in the fuel [194]. The authors in their paper presented that formaldehyde was the most abundant aldehyde in the engine exhaust, followed by acetaldehyde. The variation of formaldehyde emissions is shown in Fig. 41. Formaldehyde emissions increased when the engine load increases from 0.08 MPa to 0.38 MPa, but decreased when the engine load increased from 0.38 MPa to 0.70 MPa. Formaldehyde emissions attained the peak value at medium engine load, which was similar to that of the total hydrocarbon emissions. The formaldehyde emissions of the blended fuels were higher than those of biodiesel and the Euro V diesel fuel while the formaldehyde emissions of biodiesel were higher than those of the diesel fuel. The difference in formaldehyde emissions among the fuels were higher at low and medium loads but were lower at high engine loads. From Euro V diesel fuel to biodiesel, the increase of formaldehyde emission were 6.4%, 9.2%, 8.5%, 1.4% and 1.3%, respectively, for the engine loads of 0.08 MPa, 0.20 MPa, 0.38 MPa, 0.55 MPa and 0.70 MPa. The authors used other researchers’ ideas for their results proving. Correa [204] studied the carbonyl emissions of biodiesel blended with diesel fuel, and reported that the formaldehyde increased 2.6%, 7.3%, 17.6% and 35.5% respectively for 2%, 5%,10% and 15% of biodiesel, compared with baseline diesel fuel. The possible explanations were as follows. Firstly, since the biodiesel used in their study was produced from waste cooking oil which might contain aldehydes compounds formed during the frying or cooking process [205]. Thus, it was possible that the formaldehyde emissions of biodiesel were higher than those of Euro V diesel fuel. Secondly, biodiesel from waste cooking oil contains many short chain chemicals that favor the formation of the shortest chain aldehyde, namely, formaldehyde, during combustion [205]. Thirdly, formaldehyde could be produced by the free glycerol which was formed during the esterification process [206, 207].

Fig. 41. Effect of methanol and engine load on formaldehyde emissions [203].

They presented that with increase of methanol fraction in the blended fuel, the formaldehyde emissions increased. However, the difference between the formaldehyde emissions between biodiesel and the blended fuels were small at the engine loads of 0.55 MPa and 0.70 MPa. From biodiesel to BM15, the change of formaldehyde emissions were 59.8%, 33.2%, 16.3%, 10.3% and 11%, for the engine loads of 0.08 MPa, 0.20 MPa, 0.38 MPa, 0.55 MPa and 0.70 MPa, respectively. Their results were in agreement with other studies. For instance, Zervas et al. [167] found that the formaldehyde emissions increased with the methanol fraction, and concluded that exhaust formaldehyde was mainly produced from fuel methanol. And Chao et al. [193] studied the effect of methanol on the emissions of carbonyl compounds generated from the diesel engine. They found that the formaldehyde emissions increased when methanol increased from 5% to 15%. In addition, Zhang et al. [208] measured the formaldehyde emission on a diesel engine fueled with DME derived from methanol. They concluded that the higher formaldehyde emission was attributed to the oxygen contents in the fuel. Fig. 42 shows the variation of acetaldehyde emissions in the engine exhaust. The acetaldehyde emissions vary narrowly between 4 and 7 ppm which was similar to the results of He et al. [209] in which the acetaldehyde emissions varied between 1 and 8 ppm. In general, they found that the maximum acetaldehyde emission occurred at the engine load of 0.2 MPa. Compared with Euro V diesel fuel, the acetaldehyde emissions of biodiesel and the blended fuels were higher; and there were higher acetaldehyde emissions from the blended fuels except at certain operating conditions. At the engine load of 0.20 MPa, compared with the Euro V diesel fuel, they observed that the acetaldehyde emissions of biodiesel increased by 13% while the average acetaldehyde emissions of the blended fuels increased by 21%. Their observation followed same behaviors as other works. For example, Correa [204] also reported that the acetaldehyde increased by 1.4%, 2.5%, 5.4%, and 15.8% respectively for 2%, 5%, 10% and 15% of biodiesel, compared with baseline diesel fuel. And Arapaki et al. [206] found that acetaldehyde emission increased sharply with biodiesel–diesel blend, compared with Euro V diesel fuel, and concluded that the acetaldehyde emissions could be caused by a higher free glycerol or total glycerol content of the methyl ester. In addition, Turrio-Baldassarri et al. [210] reported a 6.3% increase of acetaldehyde emission using 20% (v/v) biodiesel. Petit [211] concluded that a decrease of fuel aromatics increased acetaldehyde emission. And acetaldehyde was the incomplete combustion product of paraffin. The decreasing aromatic content might increase the

Fig. 42. Effect of methanol and engine load on acetaldehyde emissions [203].

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

1479

Fig. 43. Effect of methanol and engine load on unburned methanol [203].

Fig. 44. Effect of methanol and engine load on 1,3-butadiene emissions [203].

paraffin content. Thus, the acetaldehyde emission would increase with the reduction of fuel aromatics. In general, there was an increase of the acetaldehyde emission with increase of methanol in the blended fuel. Fig. 43 illustrates the unburned methanol emissions. In general, their results showed that the unburned methanol emissions of the Euro V diesel fuel and biodiesel were very low. For the blended fuels, the unburned methanol emissions decreased as the engine increases from 0.08 MPa to 0.55 MPa but increased slightly from 0.55 MPa to 0.70 MPa. The possible reason was that with increase of engine load, there was an increase in fuel burned as well as an increase in the combustion temperature. The increase in the amount of methanol in the fuel would cause an increase of unburned methanol but the increase in combustion temperature led to a net decrease in the unburned methanol. They reported when the engine load increased from 0.55 MPa to 0.70 MPa, the reverse might be true, leading to an increase in unburned methanol. Compared to Euro V diesel fuel, the unburned methanol emissions of biodiesel were slightly higher because the biodiesel might contain residual methanol which was used for producing the biodiesel. The methanol content in the blended fuels boosted the unburned methanol emissions, especially at light engine load. They mentioned a researcher's idea in their work. Zervas et al. [167] reported that exhaust methanol could be produced from the unburned fuel or from a recombination of CH3 and OH radicals or CH3O and H radicals. However the last two formation pathways were more difficult than the first one. Moreover, with methanol in the blended fuel, combustion would be delayed due to the higher latent heat of evaporation and lower cetane number of methanol, in comparison with biodiesel. Thus, some of the blended fuel would be combusted in the late expansion stroke, leading to an increase of unburned methanol. 1,3-butadiene is considered as the one of the most toxic pollutants in the atmosphere because of its carcinogenic and mutagenic properties. Moreover, 1,3-butadiene can be converted to genotoxic products through photochemical reaction in the presence of nitrogen oxides [212]. For these reasons, the authors presented that 1,3-butadiene was considered as a significant toxic pollutant, which was commonly found in the vehicle emissions. The variation of 1,3-butadiene emissions is shown in Fig. 44. From 0.08 MPa to 0.38 MPa, the 1,3-butadiene emissions increased with the engine load, then decreased from 0.38 MPa to 0.70 MPa, except for Euro V diesel fuel and biodiesel. For Euro V diesel fuel and biodiesel, the 1,3-butadiene emissions increased from 0.55 MPa to 0.70 MPa. They had a number of proofs for their results from researchers as following. Takada et al. [194] studied the

unregulated emissions of a diesel engine and found that the 1,3butadiene emissions increased from 20% to 60% engine load and decreased from 60% to 95% engine load. They also believed that the formation of 1,3-butadiene was much easier to occur in O2 rich region with lower exhaust gas temperature and lower fuel equivalence ratio. Compared to Euro V diesel fuel, the 1,3- butadiene emissions of biodiesel and the BM blends were lower. The 1,3-butadiene emissions decreased 62%, 20%, 14%, and 12% on average, based on different engine loads, for biodiesel, BM5, BM10 and BM15, respectively. In addition, Zervas et al. [178] concluded that many straight-chain hydrocarbons could contribute to the formation of 1.3-butadiene through H extraction and β-scission. So the Euro V diesel fuel which contained straight-chain hydrocarbons was more liable to the formation of 1,3-butadiene. As the methanol fraction increased, 1,3-butadiene emissions also increased. However, the difference in 1,3-butadiene emissions between BM10 and BM15 was only slight. From biodiesel to BM15, the 1,3-butadiene emissions increased by 1.4 times on average, based on different engine loads. However, Merritt et al. [199] reported a decrease of 1,3-butadiene emissions when the engine was operated with ethanol–diesel blends. The addition of methanol could increase the oxygen contents leading to improvement of diffusion combustion and hence lower 1,3-butadiene emissions. On the other hand, according to Takada's conclusion mentioned above, addition of methanol leading to lower fuel equivalence ratio and lower exhaust gas temperature which could increase the 1,3butadiene. Thus, in Cheung's study, methanol itself might have positive effects on the formation of 1,3-butadiene. The authors concerned benzene, toluene and xylene (BTX); because they have been identified as carcinogenic, mutagenic, and teratogenic [213]. The main sources of benzene, toluene and xylene are unburned molecules from fuel, prosynthesis and structural modifications during combustion [200]. Table 30 shows the BTX emissions at engine loads of 0.2 MPa, 0.38 MPa, and 0.55 MPa. It can be seen from the Table 30 that benzene emissions decreased with the increase of engine load. Cheung's observations followed same behaviors as other works. Di et al. [214] found higher benzene emissions at lower engine loads. Takada et al. [194] also showed higher benzene emissions at lower engine loads and lower exhaust gas temperatures, and concluded that benzene could be easily degraded at high exhaust gas temperature. Compared with Euro V diesel fuel, the benzene emissions of biodiesel were lower. Due to the characteristics of non-light-aromatics, biodiesel had lower benzene emissions than Euro V diesel fuel [200]. With increase of methanol in the blended fuels, benzene emissions decreased. Their possible reasons were as follows. After addition of methanol in the

1480

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

blended fuel, the combustion temperature decreased, leading to the increase in benzene emissions, especially at light engine load. On the other hand, with increase of methanol, the increase of oxygen content could improve combustion and promote the degradation of benzene and hence reduce the benzene emissions. Moreover, unsaturated hydrocarbons in the fuel were precursors responsible for the formation of aromatic and PAH species [201]. Therefore, the methanol in the BM blends had a dilution effect to the aromatics precursors, leading to the reduction of the aromatics. It had been pointed out that the formation of mono and poly-nuclear aromatic compounds was related with the lack of oxygen to convert carbon atoms to carbon dioxide [200]. Thus with an increase of oxygen in the fuel, there was a reduction of benzene. Toluene and xylene emissions also decreased with engine load. However, toluene and xylene emissions had different trends compared with benzene. For toluene the lowest emissions were obtained with biodiesel, while the blended fuels and the diesel fuels had similar levels of toluene emissions. For xylene, the levels of emissions from the different fuels were almost the same. 5.9.4. Summary Experiments were conducted on a naturally-aspirated, watercooled, 4-cylinder, direct-injection diesel engine. In that experiment, the engine performance, regulated emissions and unregulated emissions were studied on a diesel engine fueled with Euro V diesel fuel, biodiesel, and three biodiesel–methanol blends (BM5, BM10 and BM15). The results lead to the following conclusions:

 Compared to the diesel fuel, biodiesel and the blended fuels had      

higher level of formaldehyde, acetaldehyde and unburned methanol emissions. With increase in methanol fraction in the blended fuel, the formaldehyde, acetaldehyde, and unburned methanol emissions increased. 1,3-butadiene emissions of biodiesel and the blended fuels were lower than those of the diesel fuel. With increasing of methanol in the fuel, 1,3-butadiene emissions increased as well. Compared to the diesel fuel, the benzene emissions of biodiesel and the blended fuels were lower. Benzene emissions also decreased with increasing of methanol in the fuel. For toluene, the lowest emissions were obtained from biodiesel while the diesel fuel and the blended fuels generated the same level of toluene. The same order of xylene was generated by all the fuels.

5.10.1. Test experimental setup and fuels The experimental system and engine specifications are shown in Fig. 36 and Table 26, respectively. The used fuels include ULSD and its blends with ethanol and 1-dodecanol. They reported that the stability of an ethanol–diesel blend depended on temperature, water contamination level and the stability additive used [216]. In that experimental work, anhydrous ethanol with a purity of 99.7% was used, and the blended fuel was stored in an air conditioned room. They found that the blended fuel containing 5% ethanol and 95% ULSD could be maintained in a closed vessel for more than 3 weeks. However, with the increase of ethanol in the blended fuel, ULSD and ethanol tended to separate. In order to prevent the separation, 1-dodecanol was employed as co-solvent. ULSD and four blended fuels were used. The four blended fuels were designed to have oxygen concentrations of 2% 4% 6% and 8%, taking into consideration the oxygen in both ethanol and 1dodecanol. The first three blends contain 1% 1-dodecanol while blend-4 requires 1.5% of 1-dodecanol to ensure good mixing. 5.10.2. Emissions testing and analysis The gaseous species in the engine exhaust were measured on a continuous basis. Unregulated gases including benzene, toluene, formaldehyde, ethanol and the like were measured with the Airsense multi-component gas analyzer. In that study, benzene, toluene and formaldehyde were calibrated directly using standard gases, while ethanol and other compounds were calibrated through an indirect way based on information provided by the equipment supplier. 5.10.3. Results and discussion The unburned ethanol concentration in the exhaust gas is illustrated in Fig. 45. In general unburned ethanol concentration decreased with increase of engine load. For blend-1, blend-2 and blend-3, it decreased from 0.08 MPa to 0.38 MPa, but increased slightly at 0.55 MPa, after that it decreased again. For example, for blend-3, it reduced from 287 ppm at 0.08 MPa to 208 ppm at 0.38 MPa, increased to 221 ppm at 0.55 MPa but again reduced to 151 ppm at 0.67 MPa. With ethanol in ULSD, the unburned ethanol concentration increased sharply, especially at low engine load. At 90.08 MPa, the concentrations were 5.6 ppm, 126 ppm, 9 160 ppm, 287 ppm and 360 ppm, respectively, for ULSD, blend-1, blend-2, blend-3 and blend-4. Their results were in agreement with other studies. In He et al. [217] work, the unburned ethanol concentration also increased sharply with the ethanol content. Merritt et al. [199] measured the unburned ethanol concentration on three

5.10. C.S. Cheung and co-workers (2008) The effect of engine load and ethanol content on engine performance, regulated emissions and unregulated emissions was investigated in Cheung's study et al. [215]. However, the effect of ethanol blending percentage on unregulated emissions is selected for this literature survey study. Table 30 Benzene, toluene and xylene emissions with different fuels at various loads [203]. mg kW
1 h
1

Euro V Biodiesel BM5 BM10 BM15

0.20 MPa

0.38 MPa

0.55 MPa

C6H6

C7H8

C8H10 C6H6

C7H8 C8H10 C6H6

C7H8 C8H10

156.24 89.85 64.68 51.91 36.00

11.74 6.29 13.97 11.58 11.06

27.19 57.49 25.26 28.14 24.82 28.48 25.53 21.57 25.49 13.21

4.75 2.53 5.12 4.68 3.57

2.49 1.37 2.10 2.38 2.14

10.59 6.75 11.98 10.45 9.91

29.67 14.23 11.06 10.60 6.34

4.91 3.86 6.44 5.19 3.78 Fig. 45. Effect of ethanol and engine load on unburned ethanol emission [215].

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Fig. 46. Effect of ethanol and engine load on formaldehyde emission [215].

Fig. 47. Effect of ethanol and engine load on acetaldehyde emission [215].

diesel engines on a test cycle and found that the concentrations increased with the increase of ethanol in the fuel. Formaldehyde is an intermediate product of the combustion of diesel fuel [194] and ethanol [218]. Formaldehyde emission, as shown in Fig. 46, was higher at higher engine loads and decreased with the addition of ethanol in ULSD. Acetaldehyde is converted from incomplete combusted ethanol [167,209,218]. In Fig. 47, acetaldehyde emissions are below 7 ppm for ULSD. For the blended fuels, with the increase of engine load, acetaldehyde emission in general decreased except that there was a slight increase at 0.67 MPa. With the addition of ethanol, it increased. The maximum acetaldehyde emission was observed 23.4 ppm when the engine operated on blend-4 at 0.08 MPa. Ethene (C2H4) and ethyne (C2H2) are the products of thermal pyrolysis from both diesel and ethanol [219,218]. The effect of ethanol content of the fuel on the concentrations of C2H4 and C2H2 in the exhaust gas, at the engine loads of 0.2 MPa, 0.38 MPa and 0.55 MPa, is shown in Table 31. For each fuel, the C2H4 and C2H2 emissions decreased with the increase of engine load. It was likely that the higher combustion temperature at higher engine load contributes to the oxidization of the pyrolytic products. After the addition of ethanol, the C2H4 and C2H2 concentrations reduced at

1481

0.38 MPa and 0.55 MPa. At 0.20 MPa, the decrease only happened for blend-2 and blend-3. For each load, the most obvious decrease occurred in blend-2. They proved the possible explanations as follows. On the one hand, the addition of ethanol could improve the diffusion combustion because of the increase of oxygen in the fuel, which could lead to the reduction of C2H4 and C2H2. On the other hand, it might cause the decrease of combustion temperature which was unfavorable for the oxidation C2H4 and C2H2. The two conflicting factors led to lower C2H4 and C2H2 for blend-2. Table 31 also illustrates the results of their experiments for 1,3butadiene which is an air toxic commonly found in the exhaust gas of diesel and petrol vehicles. At 0.38 MPa and 0.55 MPa, there were reductions of 1,3-butadiene with the blended fuel while at 0.22 MPa, there were reductions for blends 2 and 3 but slight increased for blends 1 and 4. For each fuel, the 1,3-butadiene emission decreased with the increase of engine load. In their work, at the engine speed of 1800 rev min
1 0.55 MPa was corresponding to about 67% engine load. Benzene, toluene and xylene (BTX) are air toxics emitted from many sources, including motor vehicles [118,119]. So it is necessary to investigate the BTX emissions from diesel engine fueled with ethanol–diesel blends. As shown in Table 32, benzene emission decreased with an increasing of engine load. They observed higher benzene emission under lower loads and lower exhaust temperature, and they explained that benzene was easily oxidized at high temperature. Thus, they concluded that lower engine loads gave higher BTX emissions. At the engine load of 0.20 MPa, after the addition of ethanol, they observed that benzene emission increased. At the engine loads of 0.38 MPa and 0.55 MPa, benzene emission decreased for blend-1, blend-2 and blend-3 but increased for blend-4. They reported that temperature was an important factor on BTX emissions. The addition of ethanol led to the reduction of combustion temperature, which contributed to increase in the benzene emission, especially at low engine load. However, with the addition of ethanol, the oxygen enrichment might promote the oxidization of benzene, which contributed to the reduction in benzene emission. As a result, they found that benzene emission decreased for blend-1, blend-2 and blend-3 at 0.38 MPa and 0.55 MPa, but, for blend-4, the reduction in gas temperature might dominate, leading to the increase of benzene emission. Regarding the toluene and xylene emissions, there were reductions at all engine loads. The toluene and xylene emissions were lower for blend-1, blend-2 and blend-3, but higher for blend4. So it can be anticipated that the combustion temperature and oxygen content in the fuel are opposite factors which dominated the BTX emissions. 5.10.4. Summary Experiments were conducted on a diesel engine using ethanol– ULSD blended fuels, containing 1–1.5% by volume of 1-dodecanol as the solvent. Blended fuels containing 6.1%, 12.2%, 18.2% and 24.2% by volume of ethanol, corresponding to 2%, 4%, 6% and 8% by mass of oxygen in the blended fuel, were used in the tests. The effect of engine load and ethanol content on engine performance, regulated emissions and unregulated emissions was investigated. The main summaries are listed below.

 Formaldehyde emission increased with increasing of engine 



load, but unburned ethanol, acetaldehyde, ethyne, ethene, 1,3butadiene and BTX all decreased with increasing of engine load. With the addition of ethanol in the blended fuel, the emissions of unburned ethanol and acetaldehyde increased. Formaldehyde emission decreased at high engine load, but there was no clear trend at low engine load. The hydrocarbons ethyne, ethene and 1,3-butadiene decreased sharply with the addition of ethanol at 0.55 MPa, and reduced

1482

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Table 31 Ethene, ethyne and 1,3-butadiene emissions at various engine loads [215]. 1800 (rev min
1)

ULSD Blend-1 Blend-2 Blend-3 Blend-4

0.20 MPa

0.38 MPa

0.55 MPa

C2H4 (ppm)

C2H2 (ppm)

C4H6 (ppm)

C2H4 (ppm)

C2H2 (ppm)

C4H6 (ppm)

C2H4 (ppm)

C2H2 (ppm)

C4H6 (ppm)

35.8 44.7 23.7 33.6 41

106 109 49.6 62.5 73.8

46.2 49.0 29.5 41.1 50.7

35 30.1 22 28.1 30.1

97.2 82.8 43.5 47.5 53.1

45.2 44.4 28.1 35.8 37.3

22.4 19.2 14.4 16.8 16.3

54.3 45.7 26.4 28.1 27.7

31.1 24.3 21 21.8 23.6

Table 32 Benzene, toluene and xylene emissions at various engine loads [215]. mg kWh
1

ULSD Blend-1 Blend-2 Blend-3 Blend-4

   

0.20 MPa

0.38 MPa

0.55 MPa

C6H6

C7H8

C8H10

C6H6

C7H8

C8H10

C6H6

C7H8

C8H10

79.2 95.9 97.2 112.6 153.0

17.1 8.7 9.1 9.4 13.8

69.7 58.3 38.0 55.3 66.8

57.0 54.0 53.0 48.9 63.4

8.3 4.3 4.3 4.1 5.8

33.2 28.9 18.2 24.5 25.3

28.1 23.6 20.8 26.0 30.3

3.3 2.6 2.5 1.9 3.2

18.7 17.0 10.6 12.5 13.4

slightly at 0.38 MPa, but at 0.20 MPa, the reduction of these hydrocarbons only occurred in blend-2 and blend-3. Addition of ethanol in the diesel fuel could either increase or decrease the emissions of ethyne, ethene and 1,3-butadiene, resulting in more reductions in blend-2. The effect of ethanol on BTX emissions depended on both engine load and ethanol content. At 0.20 MPa, benzene emission increased with ethanol while at 0.38 MPa and 0.55 MPa, it decreased for blend-1, blend-2 and blend-3 but increased for blend-4. Toluene and xylene reduced with ethanol in the fuel but the reduction was higher for blend-1, blend-2 and blend-3, but lower for blend-4.

5.11. M. Henke and co-workers (2005) The aim of Henke's project et al. [19] was to study the impact of using such blends on evaporative emissions by carrying out measurements with different grades of base gasoline and different blending proportions of ethanol. 5.11.1. Test experimental setup and fuels All tests were performed at AVL MTC in Haninge, Sweden, in February 2005. The AVL MTC Motor test center was an accredited laboratory for automotive testing and had been in operation for approximately 15 years. AVL MTC had experience of more than 10 years of testing for the Swedish Environmental Protection Agency and the Swedish National Road Administration. The evaporative emissions from two summer gasoline fuels (with Reid Vapor Pressures (RVPs) of 63 kPa and 70 kPa, respectively) blended with low percentages of ethanol (0%, 5%, 10% and 15%) had been measured in a VT Shed. For reference purposes E85 (85% ethanol) was also measured in the same manner. 5.11.2. Emissions testing and analysis All tests were performed using a gas-proof test container (not the fuel container mentioned below) in which the evaporative behavior of whole cars was normally tested. It was called a VT shed as both its volume and temperature were controlled (Fig. 48). A standard component of that kind of equipment was a Flame Ionization Detector (FID) for measuring the total emitted

Fig. 48. VT shed container with mass spectrometer to the left [19].

hydrocarbons. That instrument, along with an Air Sense Mass Spectrometer, was used for the tests. 5.11.3. Results and discussion Changes over time in the air levels of the measured constituent as the tests progressed were presented in their study in chart form to facilitate interpretation of the measurements. The final concentrations at the end of the tests were also presented in bar graph format. The authors reported that, unsurprisingly, the ethanol content of the vapor proved to increase with increasing ethanol content in the test container to some extent. However, the relationship was not linear. Two factors contributed to this pattern. Naturally, the vapor pressure was positively correlated to the ethanol content of the blend in the container. In addition, however, ethanol enhanced the vapor pressure according to a relationship that was not linear and peaks at relatively low ethanol contents of around 10% in ethanol–gasoline blends. This was shown in their work since the vapor contents (ppm) were virtually the same for both the 5% and 10% blends, while those of both the 0% and the E85 blends were considerably lower. Fig. 49 represents the changes over time in the ethanol concentration in the VT Shed. They indicated that butane is the main compound used to regulate the vapor pressure of gasoline. It was removed to reduce the vapor pressure when required, for instance in summer gasoline, which was used in higher ambient temperature ranges. The gasoline with the higher Reid Vapor Pressure (RVP) index was therefore expected to have a higher content of vaporizing butane. This expectation was confirmed in their tests, as shown in Fig. 50. In addition, the butane vapor pressure-enhancing effect of the ethanol blended in the base gasoline was probably maximal at contents between 5% and 10%. The authors reported that benzene is an aromatic hydrocarbon with both ozone formation and carcinogenic potential, so its

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Fig. 49. Changes over time in the ethanol concentration in the VT shed [19].

emission levels were strictly restricted. Aromatics, however, were widely used to substitute lead as an anti-knock compound in gasoline. According to their results, benzene was also created during the combustion process in engines and max concentration increased compared to base levels approx. 20% with E5 (Fig. 51). Fig. 52 shows the changes over time in the toluene concentration in the VT shed. And Fig. 53 represents the changes over time in the xylene concentration in the VT shed. Max concentration increased compared to base levels, approx. 20% (with E5). Max concentration increased compared to base levels, approximation 20% (with E5) as shown in Fig. 54. The concentrations of the measured emissions from E85 were included as a separate series since they had no information on the vapor pressure of the base gasoline used for blending. However, it probably had a relatively high RVP since this level of ethanol lowers the Reid Vapor Pressure of the final mix. It can be seen from Figs. 55–60 that the concentration at the end of the test (ppm) of butane, benzene and MTBE for E5 was more compared to other blend percentages. And the concentration at the end of the test (ppm) ethanol, toluene and xylene of for E5 was more compared to other blend percentages. 5.11.4. Summary All tests were performed using a gas-proof test container in which the evaporative behavior of whole cars was normally tested. It was called a VT shed as both its volume and temperature were controlled. The evaporative emissions from two summer gasoline fuels (with Reid Vapor Pressures (RVPs) of 63 kPa and 70 kPa, respectively) blended with low percentages of ethanol (0%, 5%, 10% and 15%) had been measured in a VT Shed. For reference purposes E85 (85% ethanol) was also measured in the same manner. The results lead to the following conclusions:

 The ethanol content of the vapor proved to increase with    

increasing ethanol content in the test container to some extent. The gasoline with the higher Reid Vapor Pressure (RVP) index was therefore expected to have a higher content of vaporizing butane. Benzene, Toluene, Xylene and Methyl Teriary Buthyl Ether (MTBE) of E85 were lower compared to other fuels. Concentration at the end of the test (ppm) of butane, benzene and MTBE for E5 was more compared to other blend percentages. Concentration at the end of the test (ppm) ethanol, toluene and xylene of for E5 was more compared to other blend percentages.

1483

Fig. 50. Changes over lime in the butane concentration in the VT shed [19].

Fig. 51. Changes over time in the benzene concentration in the VT shed [19].

Fig. 52. Changes over time in the toluene concentration in the VT shed [19].

5.12. P.M. Merritt and co-workers (2005) Merritt's project et al. [199] had generated information on the exhaust emissions effects of various blends of ethanol in diesel fuel in non-road diesel engines. 5.12.1. Test experimental setup and fuels Three heavy-duty, Tier II compliant, non-road diesel engines were used. The engines represented different fuel system and emissions control technologies and varied in displacement from 6.8 to 12.5 L. The engines characteristics are summarized in

1484

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Fig. 57. Benzene concentration at the end of the test (ppm) [19].

Fig. 53. Changes over time in the xylene concentration in the VT shed [19].

Fig. 58. Toluene concentration at the end of the test (ppm) [19].

Fig. 54. Changes over time in the MTBE concentration in the VT shed [19].

Fig. 59. Xylene concentration at the end of the test (ppm) [19].

Fig. 55. Ethanol concentration at the end of the test (ppm) [19].

Fig. 60. MTBE concentration at the end of the test (ppm) [19].

Fig. 56. Butane concentration at the end of the test (ppm) [19].

Table 33 and include the three most common types of fuel injection systems. The reference fuel for that program was No. 2D certification diesel, with a nominal sulfur content of 400 ppm. Three different blends of ethanol in that reference fuel were prepared, at 7.7%, 10%, and 15% by volume. Three additive suppliers provided material to enhance the stability and performance of the ethanol in diesel blends.

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495 Table 34 Part 89 test modes and weighting factors [199].

Table 33 Test engines characteristics [199]. Engine model Displacement (L) Rated speed (rpm) Rated power (kW (hp)) Intermediate speed (rpm) Peak torque (N-m (lbft)) Inlet restriction (kPa) Exhaust restriction (kPa) Turbocharged/intercooled Inter-cooling type Inter-cooler outlet temp. (°C) Inter-cooler ΔP (kPa) Fuel system

1485

6081HRW28 8.1 2200 224 (301) 1400

6068HF275 6.8 2000 129 (172) 1400

6125HRW02 12.5 2100 375 (500) 1500

1361 (1004)

725 (535)

1989 (1467)

2.99 7.45

2.99 7.45

2.99 7.45

Yes/Yes

Yes/Yes

Yes/Yes

Air/Air 60

Air/Air 60

Air/Air 60

12.45 (50) High pr., common rail

12.45 (50) Rotary pump line nozzle

12.45(50) Electronic unit injector

Exhaust emission characterization was performed as specified under CFR Title 40, Part 89. For non-road heavy-duty engines, the regulation outlines specific requirements for setting up the test engine and pre-test activities, as well as all aspects of conducting the testing and collection and analysis of gaseous samples. The 8-mode test cycle was utilized in that test program. Table 34 shows the Part 89 test modes and weighting factors. Two consecutive runs of the 8-mode test and two FTP smoke tests (40 CFR Parts 86 and 89) were performed for each fuel composition. In a regular 8-mode test they stabilize the engine for 5 min and sample for 5 min. To accumulate a sufficient dilute exhaust sample for unregulated emissions analysis, each mode was run for a number of minutes equivalent to its weight factor in percent (stabilization time of 5 min was unchanged). For example, a mode with a 0.10 weight factor received a 10-min sampling period. This approach extended the total sampling duration for the 8-mode test from 40 to 100 min. For the PAH and NPAH sampling, one set of collection media was used to collect a composite sample for each 8-mode test. 5.12.2. Emissions testing and analysis Their target list for unregulated emissions included the soluble organic fraction of the PM (SOF), aldehydes and ketones (ALD), ethanol (ETH), individual hydrocarbons (IHC), polycyclic aromatic hydrocarbons (PAH), and 1-nitropyrene. For each mode, SOF was determined by extracting a 50% section of the particulate-laden 90mm Pallflex filters using a Soxhlet apparatus with toluene– ethanol solvent. Solvent was evaporated from the extracted particulate filters and the filters were re-weighed. The difference in mass was the solvent-extractable material. 5.12.3. Results and discussion Soluble organic fraction of particulate matter is summarized in Table 35. SOF tended to increase with ethanol content as compared to baseline diesel fuel. SOF levels were, as they expected, highest for the low load modes 4 and 8. Mode 7 exhibited the largest difference in SOF between baseline diesel fuel and an ethanol blend (in this case the 15% blend). Individual hydrocarbon emissions results are presented in Table 36. Increasing of formaldehyde, acetaldehyde, and ethanol were observed with increasing of ethanol content. Emissions of 1,3-butadiene and benzene were reduced slightly with the ethanol blends. PAH and NPAH results are presented in Table 37. It notes that PAH and NPAH compounds are expressed in nanograms (10
9 g). In the vapor phase, acenaphthylene and fluorene were observed lower for the alcohol blends, but fluoranthene and

Mode Speed

1 Rated

2

3

4

5 6 Intermediate

7

8 Idle

Percent torque Weight factor

100 0.15

75 0.15

50 0.15

10 0.10

100 0.10

50 0.10

0 0.15

75 0.10

Table 35 Soluble organic fraction by mode for 8.1-L-engine percent of total particulate matter [199]. Fuel type

Baseline average

7.7% Ethanol

10% Ethanol

15% Ethanol

Mode Mode Mode Mode Mode Mode Mode Mode

40.5 35.9 38.2 88.4 33.6 30.8 46.7 87.9

56.3 48.8 40.2 88.0 39.7 44.1 66.5 93.6

58.2 41.4 39.4 87.6 37.1 38.4 48.8 82.9

58.0 48.6 39.0 93.0 45.1 49.5 67.7 90.0

1 2 3 4 5 6 7 8

Table 36 Unregulated emissions summary for 8.1-liter engine averaged, composite results over 8-mode test, mg/hp-h [199]. Fuel type

Baseline fuel 7.7% Ethanol

10% Ethanol

15% Ethanol

Formaldehyde Acetaldehyde Acrolein Propionaldehyde Methyl ethyl ketone Ethanol 1,3-Butadiene Methane Benzene Toluene Ethylbenzene M-& P-Xylene O-Xylene Hexane Styrene

9.56 3.70 1.87 0.68 0.53 0.32 0.90 2.09 0.81 1.00 0.51 0.85 0.39 0.03 0.12

10.52 4.68 1.43 1.18 0.09 17.65 0.68 0.53 0.69 0.90 0.42 0.61 0.38 0.07 0.11

11.00 5.51 1.59 1.22 0.09 26.89 0.68 0.15 0.72 1.17 0.55 0.89 0.43 0.16 0.10

10.21 4.71 1.83 0.83 0.59 16.58 0.92 0.32 0.70 1.61 0.53 0.74 0.34 0.11 0.07

pyrene were higher. An increasing trend with alcohol content was observable for benzo(a)anthracene and chrysene in this view. For the lighter molecular weight compounds in the particulate-phase, all compounds were lower in the ethanol blends than in the baseline diesel. For the heavier molecular weight compounds in the particulate-phase, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, and dibenzo(a, h)anthracene were all higher for the ethanol blends, but 1nitropyrene was lower. The soluble organic fraction of particulate matter is presented in Table 38. For the 6.8-L engine, smoke opacity was reduced in proportion to ethanol content for all operational modes. SOF was highest for modes 4 and 8 and in general was higher with increasing ethanol content. Results for modes 1 and 8 did not follow this trend, however, where SOF was reduced with the ethanol blended fuels. Significant increases were observed in emissions of acetaldehyde (and of ethanol) with increasing ethanol content. They reported that, emissions of 1,3-butadiene were reduced with ethanol blends, but benzene emissions were not significantly affected. Individual hydrocarbon emissions results are summarized in Table 39. PAH results are presented in Table 40. For the lighter molecular weight compounds for the vapor phase only, phenanthrene was

1486

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Table 37 PAH and NPAH compounds for 8.1-l engine, composite results over 8-mode test, ng/hp-h [199]. Fuel type

Baseline Fuel

7.7% Ethanol

Compound/phase

Vapor phase

PM phase

Vapor phase

PM phase

Vapor phase

PM phase

Vapor phase

PM phase

Naphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene Fluoranthene Pyrene Benzo(a)anthracene Chrysene Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(a)pyrene Indeno(1,2,3-c,d)pyrene Dibenzo(a,h)anthracene 1-Nitropyrene

224,515 1244 30,207 59,566 99,538 6519 2274 3674 7 16 2 2 1 1 2 0

237 146 89 471 7419 710 2390 5146 358 834 145 84 87 14 5 129

234,480 271 30,172 47,348 91,207 6443 2935 6413 16 30 1 1 0 1 0 1

84 72 51 207 3428 331 348 3741 428 830 179 155 171 27 8 68

472,781 277 35,886 56,904 103,191 6842 3266 6267 13 30 2 1 1 1 0 1

144 97 63 295 4084 368 1627 3959 403 877 183 126 136 32 10 90

219,800 49 30,678 45,485 76,198 5123 2657 5685 17 35 1 0 0 1 0 2

95 62 41 162 2244 208 919 2493 275 617 160 125 111 34 8 79

Table 38 Soluble organic fraction by mode for 6.8-l engine, percent of total particulate matter [199]. Fuel type Baseline Fuel

7.7% Ethanol

10% Ethanol

15% Ethanol

Replicate

Test 1

Test 2

Test 1

Test 2

Test 1

Test 2

Test 1 Test 2

Mode Mode Mode Mode Mode Mode Mode Mode

12.8 22.1 50.1 78.9 6.8 28.7 46.5 91.4

16.6 21.4 48.9 83.5 11.7 21.8 48.8 85.9

11.4 26.6 53.9 84.8 10.9 26.5 60.5 61.3

12.7 23.5 66.0 80.4 9.3 22.2 48.4 75.2

11.7 19.5 49.6 75.8 8.5 29.9 58.7 92.8

13.8 26.5 61.8 84.3 11.8 27.2 60.1 88.2

15.3 36.3 73.8 83.4 14.7 34.1 58.3 67.9

1 2 3 4 5 6 7 8

12.4 33.0 63.0 88.5 14.4 33.2 62.2 499.0

Table 39 Unregulated emissions summary for 6.8-liter engine averaged, composite results over 8-mode test, mg/hp-hr [199]. Compound/fuel type Baseline fuel 7.7% Ethanol

10% Ethanol

15% Ethanol

Formaldehyde Acetaldehyde Acrolein Propionaldehyde Methyl ethyl ketone Ethanol 1,3-Butadiene Methane Benzene Toluene Ethylbenzene m-& p-Xylene o-Xylene Hexane Styrene

14.88 7.56 0.75 1.39 0.30 32.82 0.56 2.37 1.79 1.80 0.51 0.95 0.60 0.36 0.11

20.11 10.82 2.68 1.81 0.16 52.66 1.03 3.11 1.82 1.83 0.76 2.08 1.50 0.48 0.19

16.56 4.82 2.04 2.35 0.15 0.44 1.70 0.71 1.78 3.05 0.90 1.36 0.63 0.11 0.26

14.77 6.27 0.47 1.32 0.13 23.22 1.40 1.14 1.68 0.84 0.68 0.97 0.50 0.26 0.18

lower for the alcohol blends, but fluoranthene and pyrene were higher. For the lighter molecular weight compounds in the particulate phase only most compounds were lower in the ethanol blends. They measured that, in the heavier molecular weight compounds for the particulate phase, all compounds except 1nitropyrene were higher in the ethanol blends. Lower emission rates were seen for 1-nitropyrene with the ethanol blends. Soluble organic fraction of particulate matter is summarized in Table 41. SOF showed consistent increases with ethanol content in

10% Ethanol

15% Ethanol

Table 40 PAH and NPAH compounds for 6.8-L engine, composite results over 8-mode test, ng/hp-h [199]. Compound/fuel type Baseline fuel 7.7% Ethanol

10% Ethanol

15% Ethanol

Formaldehyde Acetaldehyde Acrolein Propionaldehyde Methyl ethyl ketone Ethanol 1,3-Butadiene Methane Benzene Toluene Ethylbenzene m-& p-Xylene o-Xylene Hexane Styrene

14.88 7.56 0.75 1.39 0.30 32.82 0.56 2.37 1.79 1.80 0.51 0.95 0.60 0.36 0.11

20.11 10.82 2.68 1.81 0.16 52.66 1.03 3.11 1.82 1.83 0.76 2.08 1.50 0.48 0.19

16.56 4.82 2.04 2.35 0.15 0.44 1.70 0.71 1.78 3.05 0.90 1.36 0.63 0.11 0.26

14.77 6.27 0.47 1.32 0.13 23.22 1.40 1.14 1.68 0.84 0.68 0.97 0.50 0.26 0.18

Table 41 Soluble organic fraction by mode for 12.5-L engine, percent of total particulate matter [199]. Fuel type Baseline fuel

7.7% Ethanol

10% Ethanol

15% Ethanol

Replicate

Test 1

Test 2

Test 1

Test 2

Test 1

Test 2

Test 1

Test 2

Mode Mode Mode Mode Mode Mode Mode Mode

63.2 49.1 40.9 44.4 74.6 80.1 63.2 100

51.8 41.1 36.9 32.0 68.0 58.0 65.7 100

54.8 59.7 44.9 44.6 67.7 82.2 72.4 100

63.2 49.1 40.9 44.4 74.6 80.1 63.2 100

65.7 55.6 40.7 42.0 65.6 70.3 69.0 100

52.0 58.7 44.6 42.2 68.8 73.5 56.7 100

65.3 67.5 44.9 49.7 85.4 100 56.4 100

65.8 61.4 37.9 47.8 62.0 69.2 62.4 98.0

1 2 3 4 5 6 7 8

modes 2 and 4. SOF was highest in mode 8. In mode 8, there was little difference in SOF for the four fuels. Individual hydrocarbon emissions results are summarized in Table 42. Emissions of acetaldehyde and ethanol increased with increasing of ethanol content. Other aldehydes tended to increase as well. Benzene and 1,3-butadiene increased with increasing ethanol content, but were all lower than base fuel. PAH and NPAH results are presented in Table 43. For the lighter molecular weight compounds in the vapor phase, an increasing trend for pyrene was observed, and naphthalene, acenaphthene,

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Table 42 Unregulated emissions summary for 12.5-liter engine averaged, composite results over 8-mode test, mg/hp-h [199]. Compound/fuel type Baseline fuel 7.7% Ethanol

10% Ethanol

15% Ethanol

Formaldehyde Acetaldehyde Acrolein Propionaldehyde Methyl ethyl ketone Ethanol 1,3-Butadiene Methane Benzene Toluene Ethylbenzene m-& p-Xylene o-Xylene Hexane Styrene

11.04 5.23 0.97 1.42 0.13 25.12 0.56 1.47 1.01 1.65 0.70 1.12 0.49 0.27 0.09

11.78 6.65 1.25 1.11 0.12 34.51 0.74 1.01 0.98 1.60 0.57 0.73 0.34 0.15 0.08

9.16 2.78 1.05 0.93 0.12 0.36 1.16 1.64 1.13 1.09 0.43 0.89 0.42 0.03 0.11

10.50 4.60 1.23 0.95 0.15 17.11 0.21 1.66 0.57 1.20 0.47 0.74 0.39 0.20 0.11

fluoranthene were higher in the ethanol blends. Acenaphthylene and acenaphthene were lower in the ethanol blends. For the heavier molecular weight compounds for the vapor phase, benzo (a)anthracene and chrysene showed a definite increasing trend with ethanol concentration. Benzo(a)pyrene was higher in the ethanol blends. However, 1-nitropyrene was lower in the ethanol blends. In the particulate-phase decreasing trends for acenaphthylene, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene were seen with increasing ethanol content. The heavier compounds were higher for the ethanol blends in the particulate phase, but 1-nitropyrene was lower. 5.12.4. Summary The experiments were performed on three heavy-duty, Tier II compliant, non-road diesel engines. Those engines represented different fuel system and emissions control technologies and varied in displacement from 6.8 to 12.5 l. The reference fuel for that program was No. 2D certification diesel, with a nominal sulfur content of 400 ppm. Three different blends of ethanol in that reference fuel were prepared, at 7.7%, 10%, and 15% by volume. The conclusions drawn from that study are the following points:

 Emissions of benzene and 1,3-butadiene reduced with the ethanol fuels.

 No clear trends were discernable for the PAH compounds, but 1   

nitropyrene was consistently reduced with use of the ethanol blends. Increasing ethanol concentration led to higher emissions of acetaldehyde and ethanol. Emissions of toxics such as benzene and 1,3-butadiene were reduced with the use of ethanol. 1-nitropyrene decreased with use of ethanol in all cases. Heavy PAH compounds generally increased in the particulate phase with ethanol use, and although less pronounced, a general decrease in light PAH compounds in the particulate phase with ethanol use.

5.13. Overview of researchers’ works since 2004 to 1983 In a study which carried out in Australia the unregulated emissions such as BTEX and aldehydes were measured by Orbital Engine Company in 2004 [220]. The emission measurements were made using fuels comprising of 20% ethanol (E20) in gasoline and neat gasoline. Furthermore, the vehicle emissions were determined at both 6400 and 80,000 km odometer readings. Fig. 61 shows average benzene emissions from five tested cars. The

1487

Holden car decreased its benzene emissions with increased driving distance. The benzene emission was lower when the E20 fuel was used as fuel and the emission was reduced at increased driving distance. Comparative benzene emissions from the Hyundai car was that benzene emissions increased as the driving distance increased which was valid for both fuels tested. Furthermore, the Subaru car had larger benzene emissions from the E20 fuel compared to neat gasoline. From Fig. 61, it can be concluded that there was a relatively large variation in benzene emissions due to fuel and accumulated driving distance and vehicle tested. Because of this, they reported that it was difficult to make firm conclusions with respect to benzene emissions vehicle dependency. Average acetaldehyde emissions from all vehicles tested and the results are shown in Fig. 62. It can be seen from Fig.62 that increasing of accumulate driving distance resulted in an increasing of acetaldehyde emission; however the Toyota car was excluded. This seemed to be fuel independent. They mentioned that, there was a relatively large variation in acetaldehyde emissions due to fuel and accumulated driving distance and vehicle tested as shown in Fig. 62. Because of this, they reported that it was difficult to make firm conclusions with respect to formaldehyde emissions vehicle dependency. Average formaldehyde emissions from all vehicles tested is shown in Fig. 63. All of the tested vehicles had increased formaldehyde emissions with respect to increased accumulative driving distance. The relative emissions of formaldehyde were vehicle and fuel dependent. A report by Augin and co-workers in 2004 [221] with a limited distribution from Environment Canada described a series of comparative tests carried out on five vehicles using neat gasoline and ethanol–gasoline blends (with ethanol contents of 10%, 15% and 20%). The aim of their program was to compare emissions from the vehicles when using neat gasoline and oxygenated fuel. The vehicles used in the tests are listed in Table 44 and the fuel properties are shown in Table 45. The emission tests were carried out in accordance with the US Federal Test Procedure (FTP 75) and two repeats of each cycle were performed on each vehicle in order to provide a minimal measure of the repeatability, according to the authors’ report. The results of the emission tests are shown as means for the five vehicles in Tables 46–48. The presented data provided clear indications that the emissions of formaldehyde increased when using ethanol blended gasoline. The acetaldehyde emissions increased when using ethanol blended gasoline. The emissions of the measured specific hydrocarbons either decreased or increased when using ethanol blended gasoline. He et al. [222] presented a study of exhaust emission characteristics from an engine with an electronic fuel injection (EFI) system with and without a three-way catalyst (TWC) system. The engine was run on neat gasoline, and both 10% ethanol (E10) and 30% ethanol (E30) gasoline blends (Table 49). They conducted the experiment operating the engine at idle speed and using E30 as fuel. It was observed that ethanol and acetaldehyde emissions were increased with increasing percentage of ethanol blending. It was also found that the TWC system reduced acetaldehyde emissions, but had a lower conversion efficiency for ethanol. A series of emission tests from five vehicles fueled with a blend of 10% ethanol in gasoline had been carried out by AEA Technology plc (AEA Technology is a British technology company), Harwell, UK, on behalf of the UK Department of Transport in 2002 [223]. The aim of the tests was to generate data to be used as emission factors for gasoline-fueled vehicles in the European context. The five vehicles tested are listed in Table 50. The Toyota Yaris was tested twice, since significant changes in the test procedure for

1488

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Table 43 PAH and NPAH compounds for 12.5-L engine, composite results of 8-mode test, ng/hp-h [199]. Fuel type

Baseline Fuel

7.7% Ethanol

10% Ethanol

15% Ethanol

Compound/phase

Vapor phase

PM phase

Vapor phase

PM phase

Vapor phase

PM phase

Vapor phase

PM phase

Naphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene Fluoranthene Pyrene Benzo(a)anthracene Chrysene Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(a)pyrene Lndeno(1,2,3-cd)pyrene Dibenzo(a,h)anthracene 1-Nitropyrene

143,664 28,398 30,382 70,822 129,464 11,327 2583 4573 18 33 6 7 0 3 0 6

177 91 67 269 5001 549 1940 4278 238 601 71 73 51 13 5 28

190,188 22,296 32,291 56,947 107,998 9195 3162 7756 27 56 5 4 0 0 0 1

149 64 41 184 3246 332 1405 4023 368 745 130 126 93 33 6 18

154,824 23,297 31,932 74,026 124,868 10,309 3225 8929 31 76 8 5 2 3 0 1

98 56 25 151 2566 275 1113 3214 368 713 122 130 118 40 7 18

707,495 24,732 42,270 78,878 148,862 11,839 4398 11,400 66 128 8 7 4 3 0 1

106 35 25 105 2054 204 1021 2775 311 668 142 115 75 35 7 23

Fig. 63. Formaldehyde emissions (mg/km) gasoline versus E20 [220].

Fig. 61. Benzene emissions (mg/km) gasoline versus E20 [220].

Table 44 Selected data for the tested vehicles [221].

Fig. 62. Acetaldehyde emissions (mg/km) gasoline versus E20 [220].

unregulated emissions was made after the third vehicle was tested. The used fuels for the tests were neat gasoline and a blend of 10% ethanol in gasoline. According to their report, an interesting point to note is that the RVP of the neat gasoline and the blended fuel was 60 kPa and 66.5 kPa, respectively. The emission tests were conducted according to the current European test cycle, ECE/EUDC, and six of the test cycles designed by the Warren Spring Laboratory (WSL), as listed in Table 51. Their tests results indicated that the unregulated emissions were increased for a few components while the emissions were

Vehicle

Model year Engine displace ment (L)

No. of cylinders

Transmission Test inertia (kg)

Pontiac Grand Am Honda Insight Chevrolet Silverado Toyota Echo Honda Civic

1999

3.4

V6

Automatic

1590

2000

1.0

3

Automatic

966

1999

5.3

V8

Automatic

2160

2001 2001

1.5 1.6

4 4

Automatic Automatic

1136 1250

Table 45 Selected data for the used fuels in the emission tests [221]. Fuel properties

SGCa

10% Ethanol

15% Ethanol

20% Ethanol

% C by mass % H by mass % O by mass Density [g/mL]

86.7 13.6 – 0.7453

82.8 13.5 3.7 0.7497

81.0 13.5 5.5 0.7519

79.3 13.5 7.3 0.7541

a

Summer Grade Commercial baseline tests of fuel.

decreased in most cases. There were significant differences between vehicles, so for some vehicles the emissions were increased while for others they were decreased. As they expected, the emission of

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

acetaldehyde was increased in most cases. In Table 58 the numbers of increases (þ) and decreases (
) are presented. Unfortunately, the unregulated emissions were only measured from three vehicles (plus a repeated measurement on the Toyota Yaris) and there were only four comparative measurements for benzene and nitrous oxide as shown in Tables 52–57. As can be seen in Table 58, ammonia and PAH emissions were only measured from three vehicles. Schifter et al. [224] collected mean emission factors from three TWC-equipped cars running on 3%, 6% and 10% by volume ethanol–gasoline blends in Table 59. They observed that benzene and acetaldehyde emissions increased with increasing ethanol contents, while formaldehyde emissions and the ozone formation factor (g O3/g Non-Methane Organic Gases, NMOG) decreased. In an investigation by Egeback et al. in 1984 [225] five wellmaintained and carefully-checked cars without catalytic converters and one equipped with a three-way catalyst system were used. The vehicles were tested with unchanged fuel–air ratio settings (which were set for neat gasoline) with three different fuels. The used fuels were neat gasoline, 5% ethanol mixed with unleaded gasoline (E5), and 15% methanol mixed with a refineryproduced gasoline. All fuels were tested at 22 °C and the neat gasoline and ethanol mixture were also tested at þ5° and
7 °C. A comparison of the emissions from the catalyst-equipped vehicle adapted for the use of alcohol in neat lead-free gasoline can be seen in Table 60. Their results showed that formoaldehyde and PAH of E5 were lower than those of gasoline at temperature of 22 °C. But acrolein, Table 46 Emissions of aldehydes when using neat gasoline and three different blends of ethanol [221]. Vehicle

Formaldehyde

US FTP cycle

Honda Insight mg/km

Grand Am mg/km

Honda Insight mg/km

Grand Am mg/km

0% Ethanol 10% Ethanol 15% Ethanol 20% Ethanol

0.019 0.087 0.491 0.665

0.603 0.615 0.516 0.578

0.143 0.273 0.373 0.385

0.298 0.653 0.926 0.814

1489

particles and BaP of E5 observed higher than gasoline at temperature of 22 °C. As can be seen from the data in Table 60 the ambient temperature had a clear impact on the emissions, especially the particulate emissions and (thus) PAHs. Starting the engine at low temperatures was known to have a stronger effect on the emissions when using fuels with high contents of an alcohol than when using neat gasoline. In addition an extensive investigation by Egeback and coworkers in 1983 [90] was carried out in Sweden in which the amounts of both regulated and non-regulated constituents emitted were compared when using various types of gasoline, LPG, diesel oil, different blends of methanol and a blend with 23% ethanol in lead-free gasoline (E23) to fuel the following vehicles: five Saabs, five Volvos, one Volkswagen and one Mercedes Benz. Table 49 Fuel properties of ethanol gasoline fuel blends [222]. Fuel parameters

Neat gasoline

E10

E30

Density at 19 °C RON MON IBP 10% 50% 90% FBP

0.736 92.4 81.2 36.0 55.2 92.5 153.7 184.5

0.741 95.0 82.3 37.5 49.0 73.2 149.8 181.0

0.751 99.7 86.6 40.0 52.7 72.5 145.7 181.5

Table 50 Vehicles selected for emission testing and measurement of fuel economy [223]. Vehicle identifier

Model

Engine size (L)

Emission Standards

1&6 2

Toyota Yaris Vauxhall Omega Fiat Punto VW Golf Rover 416

1.0 2.2

Euro III Euro III

1.2 1.6 1.6

Euro II Euro III/IV Euro II

Mileage (km)

Acetaldehyde

3 4 5

22,000 19,000 51,000 21,000 117,000

Table 51 Test cycles [223].

Table 47 Emissions of aldehydes when using neat gasoline and three different blends of ethanol [221]. Vehicle

Formaldehyde

US FTP cycle

Toyota Echo mg/km

Honda Civic mg/km

Toyota Echo mg/km

Honda Civic mg/km

0% Ethanol 10% Ethanol 15% Ethanol 20% Ethanol

0.534 0.360 0.690 0.671

0.311 0.870 0.416 0.572

0.261 0.379 1.044 1.311

0.099 0.721 0.435 0.597

Cycle identifier

Cycle

Hot/cold start

Duration (s) Target distance (km)

1

ECE/EUDC (Dir.98/69) WSL Congested WSL Urban WSL Suburban WSL Rural WSL Motorway 90 WSL Motorway 113

Cold

1180

11.01

Hot Hot Hot Hot Hot

1030 1205 480 586 306

1.91 6.14 5.52 10.95 7.96

Hot

256

8.18

Acetaldehyde 2&8 3&9 4 & 10 5& 11 6 & 12 7 & 13

Table 48 Emissions of specific hydrocarbons when using neat gasoline and three different blends of ethanol [221]. Vehicle

Methane

US FTP cycle

Toyota Echo mg/km

Honda Civic mg/km

Toyota Echo mg/km

Honda Civic mg/km

Toyota Echo mg km

Honda Civic mg/km

Toyota Echo mg/km

Honda Civic mg/km

0% Ethanol 10% Ethanol 15% Ethanol 20% Ethanol

4.848 4.338 4.406 4.829

1.952 1.417 1.212 1.846

4.332 4.406 4.344 4.375

2.032 1.554 1.423 1.541

0.615 0.622 0.640 0.472

BDLa BDL BDL BDL

1.311 1.212 1.293 1.181

0.640 0.261 0.553 0.423

a

BDL, Below Detection Limit.

Ethylene

Acetylene

Ethylene

1490

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Table 52 Summary of FTIR emissions measurements for vehicles 4, 5 and 6, vehicle 6 Toyota (Yaris) (repeat)) running on base gasoline and E10 fuels [223]. Drive cycle

Fuel

Methane (mg/km)

1,3-butadiene (mg/km)

Formaldehyde (mg/km)

Acetaldehyde (mg/km)

Nitrous oxide (mg/km)

Benzene (mg/km)

Cold ECE

Gasoline E10 Gasoline E10

79.593 92.031 13.173 11.640

3.007 1.307 0.326 0.231

0.974 0.509 0.288 0.197

9.042 18.183 1.003 0.896

0.660 0.198 0.095 0.014

N/D 10.092 3.124 1.347

Cold EUDC

Table 53 Vehicle 4 Volkswagen (Golf) running on base gasoline and E10 fuels [223]. Drive cycle

Fuel

Methane (mg/km)

1,3-butadiene (mg/km)

Formaldehyde (mg/km)

Acetaldehyde (mg/km)

Nitrous oxide (mg/km)

Benzene (mg/km)

Cold ECE

Gasoline E10

13.009 11.977

1.739 1.120

0.079 0.074

1.619 4.365

0.012 0.388

N/D* N/D*

Cold EUDC

Gasoline E10

0.602 0.655

0.104 0.076

0.009 0.031

0.078 0.163

0.004 0.001

0.003 N/D*

Table 54 Vehicle 5 Rover (416) running on base gasoline and E10 fuels [223]. Drive cycle

Fuel

Methane (mg/km)

1,3-butadiene (mg/km)

Formaldehyde (mg/km)

Acetaldehyde (mg/km)

Nitrous oxide (mg/km)

Benzene (mg/km)

Cold ECE

Gasoline E10

69.302 50.244

4.011 2.334

0.220 0.107

13.846 12.660

N/Da N/Da

N/Da N/Da

Cold EUDC

Gasoline E10

11.260 7.247

0.183 0.107

0.124 0.039

1.225 1.408

N/Da 0.007

N/Da N/Da

a

No data presented.

Table 55 Summary 2 of FTIR emissions measurements for vehicles 4, 5 and 6 Vehicle 6 Toyota (Yaris, repeat) running on base gasoline and E10 fuels [223]. Drive cycle

Fuel

Benzene (mg/km)

Ammonia (mg/km)

Formaldehyde (mg/km)

Acetaldehyde (mg/km)

Total PAHs (mg/km)

Cold ECEþ EUDC

Gasoline E10

0.124 0.057

4.001 5.232

0.667 0.401

0.200 0.654

43.62* 44.86*

Table 56 Vehicle 4 Volkswagen (Gulf) running on base gasoline and E10 fuels [223]. Drive cycle

Fuel

Benzene (mg/km)

Ammonia (mg/km)

Formaldehyde (mg/km)

Acetaldehyde (mg/km)

Total PAHs (mg/km)

Cold ECEþ EUDC

Gasoline E10

0.347 0.056

4.567 2.755

0.114 0.072

0.049 0.178

113.71* 30.22 *

Table 57 Vehicle 5 Rover (416) running on base gasoline and E10 fuels [223]. Drive cycle

Fuel

Benzene (mg/km)

Ammonia (mg/km)

Formaldehyde (mg/km)

Acetaldehyde (mg/km)

Total PAHs (mg/km)

Cold ECE þEUDC

Gasoline E10

0.357 1.818

7.788 18.826

0.214 1.298

0.532 1.493

42.57a 66.17a

a

Average value for Cold ECEþEUDC and the following driving cycles: WSL Congested, WSL Urban,

Table 58 Numbers of increases ( þ ) and decreases (
) of unregulated emissions found in the tests using E10 compared to the tests using neat gasoline [223]. Changes

Methane

1,3-butadiene

Formaldehyde

Acetaldehyde

Nitrous oxide

Benzene

Ammonia

Increase Decrease

2 7

2 7

2 7

6 3

1 3

1 3

2 1

P 2 1

PAH

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

Table 59 Mean emission factors from three TWC-equipped cars running on 3, 6 and 10 vol. % ethanol gasoline blends [224]. Emission

g O3/g NMOG Benzene (mg/km) Butadiene (mg/km) Formaldehyde (mg/ km) Acetaldehyde (mg/ km)

3% Ethanol 6% Ethanol 10% Ethanol

Ethanol effect

3.12 7.22 0.83 1.32

3.09 7.38 0.77 0.78

3.08 8.11 0.83 1.01


þ þ/



1.12

1.25

1.62

þ

 NOX emission was decreased with using alcohol fuels in fumigation mode compared to fossil fuels, though NOX emission was increased with using alcohol fuels in blended mode in major tests. 6.2. Unregulated emissions

 Total carbonyls were increased with using alcohol fuels in both modes compared to fossil fuels in all tests.

 Formaldehyde and acetaldehyde were the predominant carbonyls 

Table 60 Emissions of regulated and non-regulated emissions generated when using neat gasoline and E5 at different ambient temperatures. US-73 test cycle [225]. Fuel

Temp. (°C) Formaldehyde (mg/km)

Gasoline 22
5 E5 22 5
6

6.6 2.3 6.3 4.2 1.4

Acrolein (mg/km)

Particles (mg/km)

o 0.1 o 0.1 1.2 o 1.2 0.6

8.2 30.1 8.5
26.8

P PAH (l/km)

B(a) P (l /km)

49
33
71

0.9
2.1
2.2

None of these vehicles was equipped with a catalyst. All the tests carried out only those involving use of E23 were of interest here. Considering both the amounts of the emissions, and their mutagenicity, the results suggested that use of E23 had both pros and cons. For example, when comparing the use of the 23% ethanol blend in gasoline with the use of neat gasoline, the emissions of ethanol and acetaldehydes increased, while emissions of polycyclic aromatic hydrocarbons (PAHs) and especially benzo(a)pyrene (BaP) were somewhat lower, as were the mutagenic effects.

6. Conclusion In this literature review work, a wide type of IC engines, such as SI and CI engines and motorcycles were collected with different operation conditions. Different percentages of alcohol blend and fumigation ratio were summarized to get informations about the effect of alcohol (methanol and ethanol) on regulated and unregulated emissions in IC engines. After testing a large number of different engine technologies and applying various operational conditions, the following general conclusion can be drawn to summarize the following points: 6.1. Regulated emissions

 CO emission was increased with using alcohol fuels in fumiga  

1491

tion mode compared to fossil fuels; however that was decreased with using alcohol fuels in blended mode in most cases. HC emission was increased with using alcohol fuels in fumigation mode compared to fossil fuels; but that was decreased with using alcohol fuels in blended mode in major cases. PM and smoke emissions were decreased with using alcohol fuels in both modes (fumigation and blended modes) compared to fossil fuels in all cases. CO2 emission was decreased with using alcohol fuels in fumigation mode compared to fossil fuels; however that was increased with using alcohol fuels in blended mode in significant tests.

   

  

in the exhaust for vehicles followed by butyraldehyde, benzaldehyde, crotonaldehyde, methacrolein, and propionaldehyde. Formaldehyde was increased with using alcohol fuels in both modes compared to fossil fuels in most experiments. Acetaldehyde was increased with using alcohol fuels in blended mode compared to fossil fuels in major cases. Unburned ethanol and methanol were increased with using alcohol fuels in both modes compared to fossil fuels in all tests. SOF was increased with using alcohol fuels in both modes compared to fossil fuels in major cases. BTEX emissions were decreased with using alcohol fuels in blended mode compared to fossil fuels in most cases, however, BTX was increased with using alcohol fuels in fumigation mode in significant tests. 1,3-butadiene emission was decreased with using alcohol fuels in both modes compared to fossil fuels in all experiments. Ethyne and ethene were decreased with using alcohol fuels in both modes compared to fossil fuels in all cases. PAHs were decreased with using alcohol fuels in blended mode compared to fossil fuels in major cases.

Acknowledgment Author is thankful to Prof. C.S. Cheung (Professor of Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong) and Prof. Khalid Zaidi (Professor, Department of Mechanical Engineering, Aligarh Muslim University, Aligarh, Uttar Pradesh, India) for their counsel and guidance during progress of this work.

References [1] Mughal HU, MMA Bhutta, Athar M, Shahid EM, Ehsan MS. The alternative fuels for four stroke compression ignition engines: performance analysis. Trans Mech Eng 2012;36(M2):155–64. [2] Kessel DC. Global warming-facts, assessment, countermeasures. J Pet Sci Eng 2000;26:157–68. [3] Goldemberg J, Johansson TB, Reddy AKN, Williams RH. Energy for the new millennium. AMB10: J Hum Environ 2001;30:330–7. http://dx.doi.org/ 10.1579/0044-7447-30.6.330. [4] Gilbert R, Peri A. Energy and transport futures. A report prepared for national round table on the environment and the economy. University of Calgary; 2005. p. 1–96. [5] Imran A, Varman M, Masjuki HH, Kalam MA. Review on alcohol fumigation on diesel engine: a viable alternative dual fuel technology for satisfactory engine performance and reduction of environment concerning emission. Renew Sustain Energy Rev 2013:739–51. [6] Tang S, Frank BP, Lanni T, Rideout G, Meyer N, Beregszaszy C. Unregulated emissions from a heavy-duty diesel engine with various fuels and emission control systems. Environ Sci Technol 2007;41(14):5037–43. [7] Sampaio MR, Rosa LP, Agosto MDA. Ethanol-electric propulsion as a sustainable technological alternative for urban buses in Brazil. Renew Sustain Energy Rev 2008;11(7):1514–29. [8] Mak FK. A study of the economics of alcohol–gasoline blend production. Energy 1985;10(9):1061–73. [9] Rosillo-Calle F, Cortez LAB. Towards ProAlcool II—a review of the Brazilian bioethanol programe. Biomass Bioenergy 1998;14(2):115–24. [10] Delgado RCOB Araujo AS, Fernandes Jr VJ. Properties of Brazilian gasoline mixed with hydrated Ethanol for flex fuel technology. Fuel Process Technol 2007;88(4):365–8.

1492

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

[11] Kisenyi JM, Savage CA, Simmoiids AC. The impact of oxygenates on exhaust emissions of six European cars. SAE Technical Paper; 1994. doi: 10.4271/ 940929. [12] Bayraktar H. An experimental study on the performance parameters of an experimental CI engine fueled with – methanol–dodecanol blends. Fuel 2008;87(2):158–64. [13] Popa M, Negurescu N, Pana C, Racovitza A. Results obtained by methanol fuelling diesel engine. SAE; 2001. doi: 10.4271/2001-01-3748. [14] Udayakumar R, Sundaram S, Sivakumar K. Engine performance and exhaust characteristics of dual fuel operation in DI diesel engine with methanol. SAE; 2004. doi: 10.4271/2004-01-0096. [15] Brusstar M, Stuhklreher M, Swain D, Pidgeon W. High efficiency and low emissions from a port-injected engine with neat alcohol fuels. SAE; 2002. doi: 10.4271/2002-01-2743. [16] Balal M. Current alternative engine fuels. Energy Sources 2005;27:569–77. [17] Bocci E, Di Carlo A, Marcelo D. Power plant perspectives for sugarcane mills. Energy 2009;34:689–98. [18] Agarwal KA. Biofuels (alcohols and biodiesel) applications as fuels for internal combustion engines. Prog Energy Combust Sci 2007. http://dx.doi. org/10.1016/j.pecs.2006.08.003. [19] Egeback KE, Henke M, Rehnlund B, Wallin M, Westerholm R. Blending of ethanol in gasoline for spark ignition engines—problem inventory and evaporative measurements. Report No. MTC 5407. AVL MTC Motortestcenter AB Box 223 SE-136 23 Haninge; 2005. [20] Data Source: U.S. Department of Energy, Alternative Fuels Data Center. Available at: 〈http://www.afdc.energy.gov/〉 [accessed 05.05.15]. [21] Wagner T, Gray D, Zarah BY, Kozinski AA. Practicality of alcohols as motor fuel. SAE; 1979. doi: 10.4271/790429. [22] Adelman H. Alcohols in diesel engine—a review. SAE; 1979. doi: 10.4271/ 790956. [23] Kim S, Dale B. Allocation procedure in ethanol production system from corn grain I. System expansion. Int J LCA 2002;7:237–43. [24] Rossilo-Calle F. Towards pro-alcohol iiπa review of the Brazilian bioethanol program. Biomass Bioenergy 1998;14(2):115e24. [25] Arbab MI, Masjuki HH, Varman M, Kalam MA, Imtenan S, Sajjad H. Fuel properties, engine performance and emission characteristic of common biodiesels as a renewable and sustainable source of fuel. Renew Sustain Energy Rev 2013;22:133–47. [26] Masum BM, Masjuki HH, Kalam MA, Rizwanul Fattah IM, Palash SM, Abedin MJ. Effect of ethanol-gasoline blend on NOx emission in SI engine. Renew Sustain Energy Rev 2013;24:209–22. [27] Hansen AC, Zhang Q, Lyne PWL. Ethanol/diesel fuel blends—a review. Bioresour Technol 2005;96:277–85. [28] Faraco V, Hadar Y. The potential of lignocellulosic ethanol production in the Mediterranean basin. Renew Sustain Energy Rev 2011;15:252–66. [29] Wang C. Combustion and emissions of a direct injection gasoline engine using biofuels. A thesis submitted to the University of Birmingham for the degree of doctor of philosophy; September 2014. [30] Data Source: The PubChemProject. USA: National Center for Biotechnology Information. At 〈https://pubchem.ncbi.nlm.nih.gov/〉 [accessed 02.06.15]. [31] Giakoumis EG, Rakopoulos CD, Dimaratos AM, Rakopoulos DC. Exhaust emissions with ethanol or n-butanol diesel fuel blends during transient operation—a review. Renew Sustain Energy Rev 2013;17:170–90. http://dx. doi.org/10.1016/j.rser.2012.09.017. [32] 〈http://www.easychem.com.au/production-of-materials/renewable-ethanol/ advantages-and-disadvantages-of-ethanol-as-a-fuel〉 [accessed 01.06.15]. [33] Hansen AC, Kyritsis DC, Lee CF. Characteristics of biofuels and renewable fuel standards. In: Vertes AA, Qureshi N, Blaschek HP, Yukawa H, editors. Biomass to biofuel—strategies for global industries. Oxford: Blackwell Publishing; 2009. [34] Ecklund EE, Bechtold RL, Timbario TJ, McCallum PW. State-of-the-art report on the use of alcohols in diesel engines. SAE 1984; No. 840118. [35] Chotwichien A, Luengnaruemitchai A, Jai-ln S. Utilization of palm oil alkyl esters as an additive in ethanol/diesel and butanol–diesel blends. Fuel 2009;88:1618–24. [36] Rideout G, Kirschenblatt M, Prakash C. Emissions from methanol, ethanol, and diesel powered urban transit buses. SAE 1994; Paper 942261. [37] Wang WG, Clark NN, Lyons DW, Yang RM, Gautam M, Bata RM, et al. Emissions comparisons from alternative fuel buses and diesel buses with a chassis dynamometer testing facility. Environ Sci Technol 1997;31:3132–7. [38] Jackson MD, Moyer CB. Alcohol fuels, in Kirk-Othmer encyclopedia of chemical technology. New York: John Wiley and Sons; 2000. [39] Meiring P, Allan RS, Hansen AC, Lyne PWL. Tractor performance and durability with ethanol–diesel fuel. Trans ASAE 1983;26:59–62. [40] Ajav EA, Singh B, Bhattacharya TK. Experimental study of some performance parameters of a constant speed stationary diesel engine using ethanol–diesel blends as fuel. Biomass Bioenergy 1999;17:357–65. [41] Chen H, Shuai S, Wang J. Study on combustion characteristics and PM emission of diesel engines using ester–ethanol/diesel blended fuels. Proc Combust Inst 2007;31:2981–9. [42] Rakopoulos CD, Antonopoulos KA, Rakopoulos DC. Experimental heat release analysis and emissions of a HSDI diesel engine fueled with ethanol/diesel fuel blends. Energy 2007;32:1791–808. [43] Rakopoulos DC, Rakopoulos CD, Kakaras EC, Giakoumis EG. Effects of ethanol/diesel fuel blends on the performance and exhaust emissions of heavy duty Dl diesel engine. Energy Convers Manage 2008;49:3155–62.

[44] Cole RL, Poola RB, Sekar R, Schaus SE, McPartlin P. Effects of ethanol additives on diesel particulate and NOx emissions. SAE 2001:2001–01-1937. [45] Kowalewicz A. Eco-diesel engine fuelled with rapeseed oil methyl ester and ethanol. Part 1: Efficiency and emission. Proc Inst Mech Eng 2005. http://dx. doi.org/10.1243/095440705  28295. [46] Lapuerta M, Armas O, Herreros JM. Emissions from a diesel–bioethanol blend in an automotive diesel engine. Fuel 2008;87:25–31. [47] Li D, Zhen H, Xingcai L, Wugao Z, Jianguang Y. Physico-chemical properties of ethanol–diesel blend fuel and its effect on performance and emissions of diesel engines. Renew Energy 2005;30:67–76. [48] William B. Methanol and ethanol—fuel or feedstock? Tecnon OrbiChem Marketing Seminar at APIC; 7 May 2015. Seoul. [49] Renewable Fuels Association. Fuel ethanol industry guidelines specifications, and procedures. RFA Publication No. 96050; 2002. [50] Oak Ridge National Laboratory. Fuel specifications and fuel properties issues and their potential impact on the use of ethanol as a transportation fuel. Phase III Project Deliverable Report Ethanol Project 2002; Available at: http://biodiesel.pl/uploads/media/fuel specifications and fuel property issues and their potential impact on the use of ethanol as a transportation fuel.pdf. [51] Prakash C. Use of Higher than 10 vol% ethanol/gasoline blends in gasoline powered vehicles, motor vehicle emissions and fuels consultant. Prepared for Transportation Systems Branch Air Pollution Prevention Directorate. Environment Canada; 1998. [52] Mishra C, Kumar N, Chauhan BS, Lim HC, Padhy M. Some experimental investigation on use of methanol and diesel blends in a single cylinder diesel engine. Int J Renew Energy Technol Res 2013;2(1):01–16. [53] Wyton Energy Consulting. Market study for the production of second generation bio-liquids. A report prepared for North East Process Industry Cluster (NEPIC); March 2011. [54] Ciniviz M, Kose H, Canli E, Solmaz O. An experimental investigation on effects of methanol blended diesel fuels to engine performance and emissions of a diesel engine. Sci Res Essays 2011;6(15):3189–99. [55] Liao SY, Jiang DM, Cheng Q, Huang ZH, Wei Q. Investigation of the cold start combustion characteristics of ethanol-gasoline blends in a constant-volume chamber. Energy Fuels 2005;19:813–9. [56] Shengliua L, Clemente ER, Tiegang H, Yanjv W. Study of spark ignition engine fuelled with methanol/gasoline fuel blends. Appl Therm Eng 2007:27–19041910. [57] Bechtold RL, Goodman MB, Timbario TA. Use of methanol as a transportation fuel. Arlington, VA: The Methanol Institute; 2007. [58] Cox F. The physical properties of gasoline/alcohol automotive fuels. U.S. Department of Energy. In: Proceedings of the alcohol fuels technology third international symposium, vol. II, May 28–31 1979. [59] American Petroleum Institute. Alcohols and ethers-a technical assessment of their application as fuels and fuel components, 2nd ed. Washington, DC: API Publication 4261; July 1988. [60] U.S. Department of Energy. Status of alcohol fuels utilization technology for highway transportation: a 1981 Perspective—vol. I—Spark-Ignition Engines. Report DOE/CE/56061-7. May 1982. [61] Rolfsen B, The Norwegian Methanol Group, Bang J. Methanol gasoline blends in Norway. In: Proceedings of the fifth international alcohol fuel technology symposium, Auckland, New Zealand; May 13–18 1982. Oslo, Norway: The National Institute of Technology. [62] Shears TW, Judd BT. Operating a vehicle fleet on methanol blend fuels—1978 to 1981. In: Proceedings of the fifth international alcohol fuel technology symposium, May 13–18 1982. Auckland, New Zealand. [63] Keller J1. Methanol fuel modification for highway vehicle use—final report. U. S. Department of Energy, published as NTIS document. July 1978. NCP/ W3683-18. [64] Liu Z, Xu S, Deng B. A Study of methanol-gasoline corrosivity and its anticorrosive agent. In: Proceedings of the tenth international symposium on alcohol fuels, Colorado Springs, CO, USA; November 7–10,1993. Chongqing, China: The Logistical Engineering Institute. [65] Schwartz S. Laboratory studies of the effects of methanol fuel on engine oil and materials. In: Proceedings of the VI International Symposium on Alcohol Fuels Technology, Ottawa, Canada. Warren, MI, USA: General Motors Research Laboratories. [66] Chevron. Gasoline and driving performance, vol. I, 2002. May 21–25,1984. Available at: 〈http://www.chevron.com/prodserv/fuels/bulletin/motorgas/1% 5Fdriving%2Dperformance/pg2.asp〉. [67] Sandström-Dahl C. Alternative fuels Investigation on emission effects of alternative fuels Literature overview. For the Norwegian Environment Agency (Miljødirektoratet) M-291|2015. Document-Ref Emission effects of biofuels M-291 2015 endelig rapport.docx, P. 2(91). [68] EU Renewable Energy Directive (RED): Directive 2009/28/EC of the European parliament and the council of 23 April 2009 on the promotion of the use of energy from renewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC; 2009. [Online]. Available at: 〈〈http:// eur-lex.europa.eu〉〉. [69] Waltera A, Rosillo-Calleb F, Dolzana P, Piacentea E, da Cunha KB. Perspectives on fuel ethanol consumption and trade. Biomass Bioenergy 2008;32 (2008):730–48. [70] BilSweden: List of E10 approved vehicles. [Online]. Available at: 〈http:// www.bilsweden.se/publikationer/aktuellt/vilka-bilar-kan-koras-pa-elO〉 [accessed 02.01.15].

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

[71] Renewable Fuels Association. Going global 2015 ethanol industry outlook; 2015. [72] 〈http://mcgroup.co.uk/news/20140207/methanol-consumption-touchedlose-63-mln-tonnes-mark.html〉 [accessed 21.10.15]. [73] 〈http://www.methanol.org/Methanol-Basics/The-Methanol-Industry.aspx〉 [accessed 21.10.15]. [74] Yang CJ, Jacksona RB. China's growing methanol economy and its implications for energy and the environment. Energy Policy 2012;41:878–84. [75] Economic impact of methanol. Methanol FACTS. Methanol Institute; July 2011. [76] Dietz W. Response factors for gas chromatograpic analysis. J Gas Chromatogr 1967;5:68–71. [77] Johnson TV. Diesel emission control in review. In: Society of Automotive Engineers World Congress. Detroit, MI: SAE International; 2010. [78] Tschoeke H, Graf A, Stein J, Kruger M, Schaller J, Breuer N, et al. Diesel engine exhaust emissions. In: Mollenhauer K, Tschoeke H, editors. Handbook of diesel engines. Berlin: Springer-Verlag; 2010. p. 417–85. [79] Morgott DA. Factors and trends affecting the identification of a reliable biomarker for diesel exhaust exposure. Crit Rev Environ Sci Technol 2013. http://dx.doi.org/10.1080/10643389.2013.790748. [80] Lagen om motorfordons avgasrening och motorbränslen (the law on motor vehicle emission and engine fuels); 2001. p. 1080. [81] Rounce PL. Engine performance and particulate matter speciation for compression ignition engines powered by a range of fossil and biofuels [Ph.D. thesis]. UK.: The University of Birmingham; 2011. [82] U.S. Department of Labor occupational safety and health administration; 2002. Available at: 〈www.osha.gov〉. [83] US EPA. Cancer risk from outdoor air toxics. Final report, vol. 1. Washington, DC;1990. [84] Törnqvist M, Kautiainen A, Gatz R, Ehrenberg L. Hemoglobin adducts in animals exposed to gasoline and diesel exhaust 1. Alkenes. J Appl Toxicol 1988;8:159–70. [85] Törnqvist M, Segerbäck D, Ehrenberg L. The rad-equivalence approach, for assessment and evaluation of cancer risks, exemplified by studies of ethylene oxide and ethane. In: Garner R, Farmer P, Steele G, Wright A, editors. Human carcinogen exposure, biomonitoring and risk assessment. Oxford: IRL Press; 1991. p. 141–55. [86] Schuetzle D, Siegl W, Jensen T, Dearth M, Kaiser E, Gorse R, Kreucher W, Kulik E. The relationship between gasoline composition and vehicle hydrocarbon emissions. A review of current studies and future research needs. Environ Health Perspect 1994;102:3–12. [87] Törnqvist M, Rannug U, Jonsson A, Ehrenberg L. Mutagenicity of methyl nitrite in Salmonella typhimurium. Mutat Res 1983;117:47. [88] Wild D, King M, Gocke E, Eckhardt K. Study of artificial flavoring substances for mutagenicity in the salmonella/microsome, basc and micronucleus tests. Food Chem Toxicol 1983;21(6):707–19. [89] Johnsson A, Bertilsson BM. Formation of methyl nitrite in engines fueled with gasoline/methanol and methanol/diesel. Environ Sci Technol 1982;16:106–10. [90] Egeback KE, Bertilsson BM. Chemical and biological characterization of exhaust emissions from vehicles fueled with gasoline, LPG and diesel. National Swedish Environmental Protection Board; 1983. SNV PM 1635. ISBN 91-7590-115-3. [91] CARB (California Air Resources Board) California Environmental Protection Agency. Cleaner burning gasoline: an assessment of its impact on ozone air quality in California. January 1998. [92] Törnqvist M, Ehrenberg L. On cancer risk estimation of urban air. Environ Health Perspect 1994;102:173–82. [93] IARC (International Agency for Research on Cancer). Monographs on the evaluation of carcinogenic risks of chemicals to humans: polynuclear aromatic compounds, part 1, Chemical, environmental and experimental data, vol. 32. Lyon, France; 1983. [94] IARC (International Agency for Research on Cancer). Monographs on the evaluation of carcinogenic risks of chemicals to humans: Diesel and gasoline engine exhausts and some Nitro-PAH, vol. 46. Lyon, France; 1989. [95] Camner P, Cothgreave I, Ewetz L, Gustavsson P, Hansson HC, Kyrklund T, Ljungquist S, Pershagen G, Victorin K, Westerholm R. Particles in the ambient air as a risk factor for lung cancer. Report 4804. Stockholm, Sweden: Swedish Environmental Protection Agency (SEPA); 1997. [96] Pott F. Dieselmotorabgas-Tierexperimentelle Ergebnisse zur Risikoabschätzung (Diesel engine exhaust—animal experimental results for the risk assessment). Ver Dtsch Ing Ber 1991:211–24 [No. 888]. [97] Pott F, Heinrich U. Relative significance of different hydrocarbons for the carcinogenic potency of emissions from various incomplete combustion processes. IARC Sci Publ 1990;104:288–97. [98] Heinrich U, Fuhst R, Dasenbrock C, Muhle H, Koch W, Mohr U. Long term inhalation exposure of rats and mice to diesel exhaust, carbon black and titanium dioxide. In: Proceedings of the 5th international inhalation symposium on toxic and carcinogenic effects of solid particles in the respiratory tract, March 1993. Hannover, Germany; 1993. [99] Heinrich U, Fahst R, Rittinghausen S, Creutzenberg O, Bellmann B, Koch W. Chronic inhalation exposure of wistar rats and two different strains of mice to diesel engine exhaust, carbon black and titanium dioxide. Inhal Toxicol 1995;7:533–56. [100] Gaffney JS, Marley NA, Martin RS, Dixon RW, Reyes LG, Popp CJ. Potential air quality effects of using ethanol–gasoline fuel blends: a field study in

[101]

[102]

[103] [104]

[105]

[106]

[107] [108]

[109]

[110]

[111] [112]

[113] [114]

[115]

[116]

[117]

[118]

[119]

[120] [121]

[122]

[123]

[124]

[125]

[126]

[127] [128]

1493

Albuquerque, New Mexico. Environ Sci Technol 1997;31:3053–61. http://dx. doi.org/10.1021/es9610388. Grosjean D, Grosjean E, Moreira L. Speciated ambient carbonyls in Rio de Janeiro, Brazil. Environ Sci Technol 2002;36:1389–95. http://dx.doi.org/ 10.1021/es0111232. Orbital Engine Company. A literature review based assessment on the impacts of a 20% ethanol gasoline fuel blend on the australian vehicle fleet. Report to Environment Australia, November 2002. 〈http://elte.prompt.hu/sites/default/files/tananyagok/AtmosphericChemistry/ ch06s04.html〉 [accessed 06.06.15]. Boström CE, Gerde P, Hanberg A, Jernström B, Johansson C, Kyrklund T, et al. Cancer risk assessment, indicators and guidelines for polycyclic aromatic hydrocarbons (PAH) in the ambient air. Environ Health Perspect 2002;110 (Suppl. 3):451–88. Ravmdra K, Sokhi R, Van Grieken R. Atmospheric polycyclic aromatic hydrocarbons: source attribution, emission factors and regulation. Atmos Environ 2008;42:2895–921. Agarwal AK, Gupta T, Shukla PC, Dhar A. Particulate emissions from biodiesel fuelled ci engines—review article. Energy Convers Manage Manuscript Draft 2014. Finlayson-Pitts BJ, Pitts Jr. JN. Chemistry of the upper and lower atmosphere. San Diego: Academic Press; 2000. Arey J, Zielinska B, Atkinson R, Winer AM, Ramdahl T, Pitts Jr. JN. The formation of nitro-PAH from the gas-phase reactions of fluoranthene and pyrene with the OH radical in the presence of NOx. Atmos Environ 1986;20:2339–45. Atkinson R, Arey J, Zielinska B, Aschmann SM. Kinetics and nitro-products of the gas-phase OH and NO3 radical initiated reactions of napthalene-d8, fluoranthene-d10 and pyrene. Int J Chem Kinet 1990;22:999–1014. Atkinson R, Arey J. Lifetimes and fates of toxic air contaminants in California's atmosphere. Final report to California Air Resources Board, Sacramento, CA; 1997. Reisen F, Arey J. Atmospheric reactions influence seasonal PAH and nitro-PAH concentrations in the Los Angeles basin. Environ Sci Technol 2005;39:64–73. Ciccioli P, Ceninato A, Brancaleoni E, Frattoni M, Zacchei P, Miguel AH, Vasconcellos P. Formation and transport of 2-nitrofluoranthene and 2nitropyrene of photochemical origin in the troposphere. J Geophys Res 1996;101:19567–81. Ramdahl T. Polycyclic aromatic ketones in environmental samples. Environ Sci Technol 1983;17:666–70. Wilson NK, McCurdy TR, Chuang JC. Concentrations and phase distributions of nitrated and oxygenated polycyclic aromatic hydrocarbons in ambient air. Atmos Environ 1995;29:2575–84. Tsapakis M, Lagoudaki E, Stephanou EG, Kavouras IG, Koutrakis P, Oyola P, et al. The composition and sources of PM2.5 organic aerosol in two urban areas of Chile. Atmos Environ 2002;36:3851–63. Tsapakis M, Stephanou EG. Diurnal cycle of PAHs, nitro-PAHs, and oxy-PAHs in a high oxidation capacity marine background atmosphere. Environ Sci Technol 2007;41:8011–7. McDonald JD, Barr EB, White RK, Chow JC, Schauer JJ, Zielinska B. Generation and characterization of four dilutions of diesel engine exhaust for a subchronic inhalation study. Environ Sci Technol 2004;38(2004):2513–22. Schauer JJ, Kleeman MJ, Cass GR, Simoneit BR. Measurement of emissions from air pollution sources, 2. C1 through C30 organic compounds from medium duty diesel trucks. Environ Sci Technol 1999;33(1999):1578–87. Schauer JJ, Kleeman MJ, Cass GR, Simoneit BR. Measurement of emissions from air pollution sources. 5. C1–C32 organic compounds from gasolinepowered motor vehicles. Environ Sci Technol 2002;36:1169–80. Grosjean D, Grosjean E, Gertler AW. On-road emissions of carbonyls from light-duty and heavy-duty vehicles. Environ Sci Technol 2001;35:45–53. Kristensson A, Johansson C, Westerholm R, Swietlicki E, Gidhagen L, Wideqvist U. Real-world traffic emission factors of gases and particles measured in a road tunnel in Stockholm, Sweden. Atmos Environ 2004;38:657–73. Loeffler KW, Koehler CA, Paul NM, De Haan DO. Oligomer formation in evaporating aqueous glyoxal and methyl glyoxal solutions. Environ Sci Technol 2006;40:6318–23. Madden MC, Dailey LA, Stonehuerner JG, Harris DB. Responses of cultured human airways epithelial cells treated with diesel exhaust extracts will vary with the engine load. J Toxicol Environ Health Part A 2003;66(2003):2281–97. U.S. Department of Health and Human Services (DHHS). Report on Carcinogens, 11th ed. Public Health Service, National Toxicology Program, 2005. Available at: 〈http://ntp.niehs.nih.gov/index.cfm?objectid ¼32BA9724-F1F6975E-7FCE50709CB4C932〉. Jakober CA, Charles MJ, Kleeman MJ, Green PG. LC–MS analysis of carbonyl compounds and their occurrence in diesel emissions. Anal Chem 2006;78:5086–93. Jakober CA, Robert MA, Riddle SG, Destaillats H, Charles MJ, Green PG, et al. Carbonyl emissions from gasoline and diesel motor vehicles. Environ Sci Technol 2008;42:4697–703. Nitsche M. Respiratory health effects of nitrogen dioxide exposure and current guidelines. Int J Environ Health Res 1999;9:39–53. Schuetzle D, Lee F, Prater T. The identification of polynuclear aromatic hydrocarbon (PAH) derivatives in mutagenic fractions of diesel particulate extracts. Int J Environ Anal Chem 1981;9:93–144.

1494

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

[129] Alsberg T, Stenberg U, Westerholm R, Strandell M, Rannug U, Sundvall A, et al. Chemical and biological characterization of organic material from gasoline exhaust particles. Environ Sci Technol 1985;19:43–50. [130] Xia T, Korge P, Weiss J, Li N, Venkatesen M, Sioutas C. Quinones and aromatic chemical compounds in particulate matter induce mitochondrial dysfunction: implications for ultrafine particle toxicity. Environ Health Perspect 2004;112(14):1347–58. [131] Keskin A, Gürü M, Altıparmak D. Influence of metallic based fuel additives on performance and exhaust emissions of diesel engine. Energy Convers Manag 2010. http://dx.doi.org/10.1016/j.enconman.2010.06.039. [132] Maricq MM. Review chemical characterization of particulate emissions from diesel engines: a review. Aerosol Sci 2007;38:1079–118. [133] Forster P, Ramaswamy V, Artaxo P, Berntsen T, Betts R, Fahey DW, et al. Changes in atmospheric constituents and in radiative forcing, in climate change the physical science basis. Cambridge, United Kingdom; New York, NY, USA: Cambridge University Press; 2007. [134] U.S. Environmental Protection Agency (US EPA). Exposure and human health reassessment of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds national academy sciences (NAS) review, 2003. Available at: 〈http://www.epa.gov/ncea/pdfs/dioxin/nas-review/〉. [135] Shahad HAK, Wabdan SK. Effect of operating conditions on pollutants concentration emitted from a spark ignition engine fueled with gasoline bioethanol blends. J Renew Energy 2015:7. [136] Kak A, Kumar N, Singh B, Singh S. Comparative study of emissions and performance of hydrogen boosted si engine powered by gasoline methanol blend and gasoline ethanol blend. SAE Technical Paper 2015; doi:10.4271/ 2015-01-1677, 4/2015. [137] Iliev S. A comparison of ethanol and methanol blending with gasoline using a 1-D engine model. Procedia Eng 2015. http://dx.doi.org/10.1016/j. proeng.2015.01.461. [138] Li L, Ge Y, Wang M, Li J, Peng Z, Song Y, et al. Effect of gasoline/methanol blends on motorcycle emissions: exhaust and evaporative emissions. Atmos Environ 2014;102:79–85. [139] Ghazikhani M, Hatami M, Safari B, Ganji DD. Experimental investigation of performance improving and emissions reducing in a two stroke SI engine by using ethanol additives. Propuls Power Res 2013;2(4):276–83. [140] Chauhan BS, Kumar N, Pal SS, Du Jun Y. Experimental studies on fumigation of ethanol in a small capacity diesel engine. Energy 2011;36:1030–8. [141] Zhang ZH, Tsang KS, Cheung CS, Chan TL, Yao CD. Effect of fumigation methanol and ethanol on the gaseous and particulate emissions of a directinjection diesel engine. Atmos Environ 2011;45:2001–8. [142] Zhang ZH, Cheung CS, Chan TL, Yao CD. Experimental investigation of regulated and unregulated emissions from a diesel engine fueled with Euro V diesel fuel and fumigation methanol. Atmos Environ 2010;44:1054–61. [143] Zhang ZH, Cheung CS, Chan TL, Yao CD. Emission reduction from diesel engine using fumigation methanol and diesel oxidation catalyst. Sci Total Environ 2009;407:4497–505. [144] Cheng CH, Cheung CS, Chan TL, Lee SC, Yao CD, Tsang KS. Comparison of emissions of a direct injection diesel engine operating on biodiesel with emulsified and fumigated methanol. Fuel 2008;87:1870–9. [145] Cheng CH, Cheung CS, Chan TL, Lee SC, Yao CD. Experimental investigation on the performance, gaseous and particulate emissions of a methanol fumigated diesel engine. Sci Total Environ 2008;389:115–24. [146] Ajav EA, Singh B, Bhattacharya TK. Performance of a stationary diesel engine using vaporized ethanol as supplementary fuel. Biomass Bioenergy 1998;15:493–502. [147] Hayes TK, Savage LD, White RA, Sorenson SC. The effect of fumigation of different ethanol proofs on a turbocharged diesel engine. SAE paper No. 880497; 1988. p.10. [148] Broukhiyan EMH, Lestz SS. Ethanol fumigation of a light duty automotive diesel engine. SAE Paper No. 811209; 1981. [149] Heisey JB, Lestz SS. Aqueous alcohol fumigation of a single-cylinder Dl diesel engine. SAE technical paper No. 4271/811208; 1981. [150] Houser KR, Lestz SS, Dukovich M, Yasbin RE. Methanol fumigation of a light duty automotive diesel engine. SAE paper No. 801379; 1980. [151] Varol Y, Oner C, Oztop HF, Altun S. Comparison of methanol, ethanol, or nbutanol blending with unleaded gasoline on exhaust emissions of an SI engine. Energy Sources Part A Recovery Util Environ Effects 2014. http://dx. doi.org/10.1080/15567036 2011.572141, 04/2014. [152] Surawski NC, Ristovski ZD, Brown RJ, Situ R. Gaseous and particle emissions from an ethanol fumigated compression ignition engine. Energy Convers Manag 2012;54:145–51. [153] Tsang KS, Zhang ZH, Cheung CS, Chan TL. Reducing emissions of a diesel engine using fumigation ethanol and a diesel oxidation catalyst. Energy Fuels 2010;24:6156–65. [154] Cheung CS, Cheng C, Chan TL, Lee SC, Yao C, Tsang KS. Emissions characteristics of a diesel engine fueled with biodiesel and fumigation methanol. Energy Fuels 2008;22:906–14. [155] Abu-Qudais M, Haddad O, Qudaisat M. The effect of alcohol fumigation on diesel engine performance and emissions. Energy Convers Manag 2000;41:389–99. [156] Schroeder AR, Savage LD, White RA, Sorenson SC. The effect of diesel injection timing on a turbocharged diesel engine fumigated with ethanol. SAE paper No. 880496; 1988. p. 11.

[157] Pannirselvam A, Ramajayam M, Curumani V, Arulselvan S, Karthikeyan G. Experimental studies on the performance and emission characteristics of an ethanol fumigated diesel engine. Int J Eng Res Appl 2012;2:1519–27. [158] Hebbar CS, Anantha KB. Control of NOx from a DI diesel engine with hot EGR and ethanol fumigation: an experimental investigation. 10SR J Eng 2012;2:45–53. [159] Karavalakis G, Short D, Vu D, Villela M, Russell R, Jung H. Regulated emissions, air toxics, and particle emissions from SI-DI light-duty vehicles operating on different iso-butanol and ethanol blends. SAE Int 2014. http://dx.doi. org/10.4271/2014-01-1451. [160] Surawski NC, Miljevic B, Roberts BA, Modini RL, Situ R, Brown RJ. Particle emissions, volatility, and toxicity from an ethanol fumigated compression ignition engine. Environ Sci Technol 2009;44:229–35. [161] Siegl W, Richert J, Jensen T, Schuetzle D. Improved emissions speciation methodology for phase II of the auto/oil air quality improvement research program—hydrocarbons and oxygenates. SAE Technical Paper; 1993. doi: 10.4271/930142. [162] Karavalakis G, Short D, Hajbabaei M, Vu D. Criteria emissions, particle number emissions, size distributions, and black carbon measurements from PFI gasoline vehicles fuelled with different ethanol and butanol blends. SAE Technical Paper; 2013. doi: 10.4271/2013-01-1147. [163] Schifter I, Diaz L, Rodriguez R, Salazar L. Oxygenated transportation fuels, evaluation of properties and emission performance in light-duty vehicles in Mexico. Fuel 2011. http://dx.doi.org/10.1016/j.fuel.2010.09.034. [164] Graham LA, Belisle SL, Baas CL. Emissions from light duty gasoline vehicles operating on low blend ethanol gasoline and E85. Atmos Environ 2008. http: //dx.doi.org/10.1016/j.atmosenv.2008.01.061. [165] Storey J, Barone T, Norman K, Lewis S. Ethanol blend effects on direct injection spark-ignition gasoline vehicle particulate matter emissions. SAE Int J Fuels Lubr 2010. http://dx.doi.org/10.4271/2010-01-2129. [166] Karavalakis G, Durbin TD, Shrivastava M, Zheng Z. Impacts of ethanol fuel level on emissions of regulated and unregulated pollutants from a fleet of gasoline light-duty vehicles. Fuel 2012. http://dx.doi.org/10.1016/j. fuel.2011.09.021. [167] Zervas E, Montagne X, Lahaye J. Emission of alcohols and carbonyl compounds from a spark ignition engine, influence of fuel and air/fuel equivalence ratio. Environ Sci Technol 2002;36:2414–21. http://dx.doi.org/10.1021/ es010265t. [168] Elghawi UM, Mayouf AM. Carbonyl emissions generated by a (SI/HCCI) engine from winter grade commercial gasoline. Fuel 2014;116:109–15. http: //dx.doi.org/10.1016/j.fuel.2013.07.124. [169] Karavalakis G, Bakeas E, Stournas S. Influence of oxidized biodiesel blends on regulated and unregulated emissions from a diesel passenger car. Environ Sci Technol 2010;44:5306–12. [170] Ban-Weiss GA, McLaughlin JP, Harley RA, Kean AJ, Grosjean E, Grosjean D. Carbonyl and nitrogen dioxide emissions from gasoline- and diesel-powered motor vehicles. Environ Sci Technol 2008;42:3944–50. [171] Durbin TD, Miller JW, Younglove T, Huai T, Cocker K. Effects of fuel ethanol content and volatility on regulated and unregulated exhaust emissions from the latest technology gasoline vehicles. Environ Sci Technol 2007;41:4059– 64. [172] Reuter RM, Hochhauser AM, Benson JD, Koehl WJ, Burns VR, Painter LJ, et al. Effects of oxygenated fuels on RVP on automotive emissions – auto/oil air quality improvement program. SAE technical paper No. 920326; 1992. [173] Mayotte SC, Lindhjem CE, Rao V, Sklar MS. Reformulated gasoline effects on exhaust emissions: phase 1; initial investigation of oxygenate, volatility, distillation, and sulfur effects. SAE technical paper No. 941973; 1994. [174] Mayotte SC, Rao V, Lindhjem CE, Sklar MS. Reformulated gasoline effects on exhaust emissions: phase 2; continued investigation of the effects of fuel oxygenate content, oxygenate type, sulfur, olefins, and distillation parameters. SAE technical paper No. 941974; 1994. [175] Knoll K, West B, Clark W, Graves R, Orban J, Przesmitzki S, et al. Effects of intermediate ethanol blends on legacy vehicles and small non-road engines, Report 1 – Updated. Final Report. NREL/TP-540-43543. National Renewable Energy Laboratory; February 2009. [176] Stump F, Knapp K, Racy W. Influence of ethanol blended fuels on the emissions from three pre-1995 light-duty passenger vehicles. J Air Waste Manage Assoc 1996;46:1149–61. [177] Aubin K, Graham L. The evaluation of ethanol–gasoline blends on vehicle exhaust and evaporative emissions: phase 1. Report by Environment Canada, Emissions Research and Measurement Division; October 2002. [178] Zervas E, Montagne X, Lahaye J. Influence of fuel and air/fuel equivalence ratio on the emission of hydrocarbons from a SI engine. 1. Experimental findings. Fuel 2004;83:2301–11. [179] Poulopoulos SG, Samaras DP, Philipopoulos CJ. Regulated and unregulated emissions from an internal combustion engine operating on ethanolcontaining fuels. Atmos Environ 2001;35:4399–406. [180] Montero M, Duane M, Manfredi U, Astorga C, Martini G, Carriero M. Hydrocarbon emission fingerprints from contemporary vehicle/engine technologies with conventional and new fuels. Atmos Environ 2010;44:2167–75. [181] Duffy BL, Nelson PF, Ye Y, Weeks IA, Galbally IE. Emissions of benzene, toluene, xylenes, and 1, 3-butadiene from a representative portion of the Australian car fleet. Atmos Environ 1998;32:2693–704.

M.A. Ghadikolaei / Renewable and Sustainable Energy Reviews 57 (2016) 1440–1495

[182] Dupetris C, Giglio V, Police G, Prati MV. The influence of gasoline formulation on combustion and emissions in spark-ignition engines. SAE technical paper No. 932679; 1993. [183] Yao C, Yang X, Raine RR, Cheng C, Tian Z, Li Y. The effects of MTBE/ethanol additives on toxic species concentration in gasoline flame. Energy Fuels 2009;23:3543–8. [184] Yang HH, Liu TC, Chang CF, Lee E. Effects of ethanol-blended gasoline on emissions of regulated air pollutants and carbonyls from motorcycles. Appl Energy 2012;89:281–6. [185] Pang X, Mu Y, Yuan J, He H. Carbonyls emission from ethanol–blended gasoline and biodiesel–ethanol–diesel used in engines. Atmos Environ 2008;42:1349–58. [186] Leong ST, Muttamara S, Laortanakul P. Applicability of gasoline containing ethanol as Thailand's alternative fuel to curb toxic VOC pollutants from automobile emission. Atmos Environ 2002;36:3495–503. [187] Zhao H, Ge Y, Tan J, Yin H, Guo J, Zhao W, et al. Effects of different mixing ratios on emissions from passenger cars fueled with methanol/gasoline blends. J Environ Sci 2011;23(11):1831–8 2011. [188] Wei YJ, Liu SH, Liu FJ, Liu J, Zhu Z, Li GL. Formaldehyde and methanol emissions from a methanol/gasoline fueled spark-ignition (SI) engine. Energy Fuels 2009;23(6):3313–8. [189] Zhang ZH, Cheung CS, Chan TL, Yao CD. Experimental investigation on regulated and unregulated emissions of a diesel/methanol compound combustion engine with and without diesel oxidation catalyst. Sci Total Environ 2010;408:865–72. [190] Sakamoto T, Sato Y, Noda A, Yamamoto T. Reduction of unburnt methanol and formaldehyde emissions form methanol fueled vehicles—acceleration of oxidative reaction on catalyst by pre-catalyst installation and its heating. SAE Technical Paper No. 960238;1996. [191] Kim C, Foster DE. Aldehyde and unburned fuel emission measurement form a methanol fueled Texaco stratified charge engine. SAE Technical Paper No. 852120; 1985. [192] Lipari F, Keski-hynnila D. Aldehyde and unburned fuel emissions form methanol-fueled heavy-duty diesel engines. SAE Technical Paper No. 860307. 1986. [193] Chao HR, Lin TC, Chao MR, Chang FH, Huang C, Chen CB. Effect of methanolcontaining additive on the emission of carbonyl compounds from a heavyduty diesel engine. J Hazard Mater 2000;B73:39–54. [194] Takada K, Yoshimura F, Ohga Y, Kusaka J, Daisho Y. Experimental study on unregulated emission characteristics of turbocharged DI diesel engine with common rail fuel injection system. SAE Technical Paper No. 2003-01-3158; 2003. [195] Alander TJ, Leskinen AP, Raunemaa TM. Characterization of diesel particulates effects of fuel reformulation, exhaust after treatment and engine operating on particle carbon composition and volatility. Environ Sci Technol 2004;38:2707–14. [196] Lin TC, Chao MR. Assessing the influence of methanol-containing additive on biological characteristics of diesel exhaust emissions using microtox and mutatox assays. Sci Total Environ 2002;284:61–74. [197] Zervas E, Montagne X, Lahaye J. Emission of specific pollutants from a compression ignition engine. Influence of fuel hydrotreatment and fuel/air equivalence ratio. Atmos Environ 2001;35:1301–6. [198] Flynn PF, Durrett RP, Hunter GL, Loye AO, Akinyemi OC. Diesel combustion: an integrated view combining laser diagnostics, chemical kinetics, and empirical validation. SAE Technical Paper No.1999-01-0509;1999. [199] Merritt MP, Ulmet V, McCormick RL, Mitchell WE, Baumgard KJ. Regulated and unregulated exhaust emissions comparison for three tier nonroad diesel engines operating on ethanolediesel blends. SAE Technical Paper No. 2005-01-2193; 2005. [200] Correa SM, Arbilla G. Aromatic hydrocarbons emissions in diesel and biodiesel exhaust. Atmos Environ 2006;40:6821–6. [201] Inal F, Senkan SM. Effect of the oxygenate additives on polycyclic aromatic hydrocarbons (PAHs) and soot formation. Combust Sci Technol 2002;174:1–19. [202] Nelson PF, Tibbett AR, Day SJ. Effects of vehicle type and fuel quality on real world toxic emissions from diesel vehicles. Atmos Environ 2008;42:5291–303. [203] Cheung CS, Zhu L, Huang Z. Regulated and unregulated emissions from a diesel engine fueled with biodiesel and biodiesel blended with methanol. Atmos Environ 2009;43:4865–72. [204] Correa SM, Arbilla G. Carbonyl emissions in diesel and biodiesel exhaust. Atmos Environ 2008;42:769–75.

1495

[205] Guarieiro LLN, Pereira PAP, Torres EA, da Rocha GO, de Andrade JB. Carbonyl compounds emitted by a diesel engine fuelled with diesel and biodiesel– diesel blends: sampling optimization and emissions profile. Atmos Environ 2008;42:8211–8. [206] Arapaki N, Bakeas E, Karavalakis G, Tzirakis E, Stournas S, Zannikos F. Regulated and unregulated emissions characteristics of diesel vehicle operating with diesel biodiesel blend SAE 2007 01-0071; 2007. [207] Da Silva TO, Pereira PA, de P. Influence of time, surface-to-volume ratio, and heating process (continuous or intermittent) on the emission rates of selected carbonyl compounds during thermal oxidation of palm and soybean oils. J Agric Food Chem 2008;56:3129–35. [208] Zhang YS, Yu JZ, Mo CL, Zhou SR. A Study on combustion and emission characteristics of small DI diesel engine fueled with dimethyl ether. SAE 2008-32-0025; 2008. [209] He BQ, Shuai SJ, Wang JX, He H. The effect of ethanol blended diesel fuels on emissions from a diesel engine. Atmos Environ 2003;37:4965–71. [210] Turrio-Baldassarri L, Battistelli CL, Conti L, Crebelli R, De Berardis B, Iamiceli AL, et al. Emission comparison of urban bus engine fueled with diesel oil and biodiesel blend. Sci Total Environ 2004;327:147–62. [211] Petit A, Montagne X. Effects of the gasoline composition on exhaust emissions of regulated and speciated pollutants. SAE No. 932681; 1993. [212] Victorin K, Margareta S. A method for studying the mutagenicity of some gaseous compounds in Salmonella typhimurium. Environ Mol Mutagen 1998;11:65–77. [213] Krahl J, Munack A, Schroder O, Dutz M, Bunger J. Exhaust gas emissions and health effects from biodiesel, fossil diesel fuel, and swedish low sulfur diesel fuel MKI ASAE 02 6082; 2002. [214] Di Y, Cheung CS, Huang Z. Experimental investigation on regulated and unregulated emissions of a diesel engine fueled with ultra-low sulfur diesel fuel blended with biodiesel from waste cooking oil. Sci Total Environ 2009;407:835–46. [215] Cheung CS, Di Y, Huang Z. Experimental investigation of regulated and unregulated emissions from a diesel engine fueled with ultralow-sulfur diesel fuel blended with ethanol and dodecanol. Atmos Environ 2008;42:8843–51. [216] Jackson MM, Corkwell KC, Degroote CC. Study of diesel and ethanol blends stability. SAE 2003 01-3191; 2003. [217] He BQ, Wang JX, Yan XG, Tian X, Chen H. Study on combustion and emission characteristics of diesel engines using ethanol blended diesel fuels. SAE 2003-01-0762; 2003. [218] Taylor PH, Shanbhag S, Dellinger B. The high-temperature pyrolysis and oxidation of methanol and ethanol: experimental results and comparison with vehicle emission tests. SAE No. 941904;1994. [219] Tosaka S, Fujiwara Y, Murayama T. The effect of fuel properties on diesel engine exhaust particulate formation SAE No. 890421; 1989. [220] Orbital Engine Company. Market barriers to the uptake of bio fuels study testing gasoline containing 20% ethanol (E20), Phase 2B Final Report to the Department of the Environment and Heritage 2004; Available at: 〈http:// www.deh.gov.au/atmosphere/ethanol/publications/biofuels-2004/pubs/pha se2b-final-report.pdf〉. [221] Augin K, Graham L. The evaluation of ethanol–gasoline blends on vehicle exhaust and evaporative emissions, phase 1 updated 10/25/02. ERMD Report. Report: 00-64. Environmental Technology Centre, Emissions Research and Measurement Division, Environment Canada; 2004. [222] He B, Wang J, Hao J, Yan X, Xiao J. A study on emissions characteristics of an EFI engine with ethanol blended gasoline fuels. Atmos Environ 2003;37:949–57. [223] Reading A, Norris J, Feest A, Payne E. Ethanol emissions testing, E and E/ DDSE/02/021 Issue 3, AEAT Unclassified 2002; Available at: 〈http://www.dft. gov.uk/stellent/groups/dft_roads/documents/page/dft_roads_032580.pdf〉. [224] Schifter I, Vera M, Diaz L, Guzman E, Ramos F, Lopez-Salinas E. Environmental implications on the oxygenation of gasoline with ethanol in the metropolitan area of Mexico city. Environ Sci Technol 2001;35:1893–901. [225] Egeback KE, Tejle G, Laveskog A. Investigation of regulated and nonregulated emissions when using different fuel/engine combinations. Report: SNV PM 1812. The Swedish Environmental Protection Board (Naturvårdsverket); 1984.