Project Work 2.docx

ABSTRACT In the development of internal combustion engines, there has been a continuous effort to reduce fuel consumption and exhaust emissions. Improved fuel efficiency with reduced exhaust gas emissions is one of the major challenges that engineers and scientists in the automotive industry and are facing. Also in recent years there has been great concern that, the internal combustion engine is predominantly responsible for atmospheric pollution, which is detrimental to human health and environmental damage. Consequently, research engineers have been striving to reduce the quantity of pollutants emitted from exhaust system without sacrificing power and fuel consumption. The incomplete burning of the air-fuel mixture in the combustion chamber produces pollutants. The major pollutants emitted from the exhaust due to incomplete combustion are, unburnt hydrocarbons (UBHC), oxides of nitrogen (NOX) and highly poisonous carbon monoxide (CO). If however combustion is 100% complete the only products being expelled from the exhaust would be water vapour, which is harmless, and carbon dioxide, which is inert gas and, as such, it is not directly harmful to humans. However, such ideal situation is not possible and researchers are constantly trying to optimize combustion condition to the extent possible. One such methodology is the concept of lean burn technology. To achieve complete and clean combustion with reduced emissions, the lean burn technology is one of the viable technique for internal combustion engines. Lean burn technology burn the air-fuel mixture completely or almost completely, in an efficient manner, so iv that fuel consumption is reduced and the level of pollutants are with limits. Hence, lean combustion is a preferred concept for reducing exhaust emissions for meeting stringent emission standards. Factors limiting the efficiency of a conventional engine are pumping losses and the expansion ratio is identical to the compression ratio. In a conventional spark ignition engine, the compression ratio is equal to the expansion ratio. Further, the load controls in these engines are performed through throttling, which is mainly responsible for poor part load efficiency. In SI engines, the compression ratio is restricted by the combustion process, but the expansion ratio can be extended. The engine with higher expansion ratio than compression ratio is referred to as Extended Expansion Engine (EEE). The principle of extended expansion applied to four stroke spark ignition (SI) engine is based on Atkinson cycle which has a larger expansion ratio (ER) than effective compression ratio (CR), unlike a conventional Otto-cycle, where CR is equal to ER. Raising the ER results in simultaneous 1 DEPT. OF MECHANICAL ENGINEERING 2018-19

raise in the CR. However, by suitably modifying the intake valve closure timing (IVCT), it is practically possible to increase the ER alone without adversely increasing the CR. Late closing of the intake valve modifies the p-V diagram of Otto cycle into what is know as OttoAtkinson cycle or modified Atkinson cycle. One of the practical method to increase the efficiency of engine at part load is by operating the engine on Otto-Atkinson cycle, as referred above. Considering the above advantages of lean burn engine and extended expansion concept, in the present work an attempt is made to apply extended v expansion concept to a four-stroke lean burn engine to study its performance and emission characteristics. A thermodynamic modeling of extended expansion lean burn has been developed to predict the performance and emission characteristics. Experimentally a single cylinder four-stroke water-cooled diesel engine has been converted to operate as SI engine. To achieve lean combustion the following modification were done, combustion chamber was modified to enhance and swirl and squish, copper as a catalyst was coated on the cylinder head and piston crown, and high energy transistorized coil ignition (TCI) system was used to ignite lean mixture. Extended expansion was achieved by varying ER/CR ratio. Experiments were carried out for ER/CR ratio 1, 1.25, 1.5, 1.75 and 2. CR is maintained constant and ER ratio is increased to achieve different ER/CR ratio. By means of late closing of intake valve and adjusting clearance volume of the base engine this was achieved. The top dwell of the intake cam were increased to delay intake valve closing. Four different top dwell were formed in the camshaft to achieve the intake valve closing timing 93º 113º 125º, 134º after BDC corresponding to the ER/CR ratio of 1.25, 1.5, 1.75 and 2 respectively. A side draught carburetor was used in the modified engine. Since delay of IVC increases, the quantity of charge pushed back also increases, thus lesser amount of charge will be retained inside the engine cylinder. In order to prevent back flow of charge through the carburetor in to the surge tank, a suitable reed valve was used. Different parametric studies were carried out by simulation and experiments.

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CHAPTER -I

1.0 INTRODUCTION The Diesel engine (also known as a compression-ignition or CI engine), named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel, which is injected into the combustion chamber, is caused by the elevated temperature of the air in the cylinder due to the mechanical compression (adiabatic compression). Diesel engines work by compressing only the air. This increases the air temperature inside the cylinder to such a high degree that atomised Diesel fuel injected into the combustion chamber ignites spontaneously. With the fuel being injected into the air just before combustion, the dispersion of the fuel is uneven; this is called a heterogenous air-fuel mixture. The process of mixing air and fuel happens almost entirely during combustion, the oxygen diffuses into the flame, which means that the Diesel engine operates with a diffusion flame. The torque a Diesel engine produces is controlled by manipulating the air ratio; this means, that instead of throttling the intake air, the Diesel engine relies on altering the amount of fuel that is injected, and the air ratio is usually high. The Diesel engine has the highest thermal efficiency (engine efficiency) of any practical internal or external combustion engine due to its very high expansion ratio and inherent lean burn which enables heat dissipation by the excess air. A small efficiency loss is also avoided compared with two-stroke non-direct-injection gasoline engines since unburned fuel is not present at valve overlap and therefore no fuel goes directly from the intake/injection to the exhaust. Low-speed Diesel engines (as used in ships and other applications where overall engine weight is relatively unimportant) can reach effective efficiencies of up to 55%. Diesel engines may be designed as either two-stroke or four-stroke cycles. They were originally used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in submarines and ships. Use in locomotives, trucks, heavy equipment and electricity generation plants followed later. In the 1930s, they slowly began to be used in a few automobiles. Since the 1970s, the use of Diesel engines in larger on-road and off-road vehicles in the US has increased. According to Konrad Reif, the EU average for Diesel cars accounts for 50% of the total newly registered. 3 DEPT. OF MECHANICAL ENGINEERING 2018-19

1.1 VALVE TIMING DIAGRAM A valve timing diagram is a graphical representation of the opening and closing of the intake and exhaust valve of the engine, The opening and closing of the valves of the engine depend upon the movement of piston from TDC to BDC, This relation between piston and valves is controlled by setting a graphical representation between these two, which is known as valve timing diagram. The valve timing diagram comprises of a 360 degree figure which represents the movement of the piston from TDC to BDC in all the strokes of the engine cycle, which is measured in degrees and the opening and closing of the valves is controlled according to these degrees. Why do we Need Valve Timing diagram?

The normal engine completes around 100000 cycles per minute, as we know there are number of processes involve in a single cycle (from the intake of the air-fuel mixture to the exhaust of the combustion residual) of a internal which makes it necessary to be equipped with an effective system that can enable 

Synchronization between the steps of a cycle of the engine from intake of air-fuel ratio to the exhaust of combustion residual.



Complete seizure of the combustion chamber at the instant at which the combustion of air-fuel mixture takes place as the leakage can cause damage to the engine and can be hazardous.

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Provide engine with a mixed air and fuel or air in case of diesel engine when required (at the time of suction) which is the necessity of the engine. 4 DEPT. OF MECHANICAL ENGINEERING 2018-19

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Provide the exit for the combustion residual so that the next cycle of the engine can take place.

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Ideal timing for the opening and closing of the inlet and outlet valve which in turn protect the engine from defects like knocking or detonation.

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A high compression ratio required to combust the fuel especially in case of diesel engine by overlapping the closing of the valve.

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The cleaning of engine cylinder which in turn maintain the quality of combustion and decreases wear and tear inside the cylinder.

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The study of the details of the combustion that is required for the modification of the power of the engine. So due to these reasons a engine weather it is 2-stroke or 4-stroke is designed according to the valve timing diagram, so that the movement of piston from TDC to BDC is provided with the ideal timing of opening and closing of the intake and exhaust valves respectively.

1.2 THEORETICAL VALVE TIMING DIAGRAM

Suction Stroke- The engine cycle starts with this stroke, Inlet valve opens as the piston which is at TDC starts moving towards BDC and the air-fuel mixture in case of petrol and fresh air in case of diesel engine starts entering the cylinder, till the piston moves to BDC.

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Compression Stroke- After the suction stroke the piston again starts moving from BDC to TDC in order to compress the air-fuel (petrol engine) and fresh air (diesel engine) which in turn raises the pressure inside the cylinder which is essential for the combustion of the fuel. The inlet valve closes during this operation to provide seizure of the chamber for the compression of the fuel. Expansion Stroke- After compressing the fuel, the combustion of the fuel takes place which in turn pushes the piston which is at TDC towards BDC in order to release the pressure developed by the combustion and output is obtained. Exhaust Stroke- After expansion stroke the piston which is at BDC starts moving towards TDC followed by the opening of exhaust valve for the removal of the combustion residual Exhaust valve closes after the piston reaches TDC.

1.3 ACTUAL VALVE TIMING DIAGRAM

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Suction stroke of 4-stroke engine the inlet valve opens 10-20 degree advance to TDC for the proper intake of air-fuel (petrol) or air (diesel), which also provides cleaning of remaining combustion residuals in the combustion chamber. 6 DEPT. OF MECHANICAL ENGINEERING 2018-19

When the piston reaches BDC the compression stroke starts and again the piston starts



moving towards TDC ,The inlet valve closes 25-30 degree past the BDC during the compression stroke, which provide complete seizure of the combustion chamber for the compression of air-fuel(petrol engine)and air(diesel engine). During the compression stroke as the piston moves towards TDC, combustion of fuel

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takes place 20-35 degree before TDC which provides the proper combustion of fuel and proper propagation of flame. The expansion strokes starts due to the combustion of fuel which in turn releases the



pressure inside the combustion chamber and provide rotation to the crank shaft, the piston moves from TDC to BDC during expansion stroke which continuous 30-50 degree before BDC. 

The exhaust valve opens 30-50 degree before BDC which in turn starts the exhaust stroke and the exhaust of the combustion residual takes place with movement of the piston from BDC to TDC which continues till the 10-20 degree after the piston reaches TDC. As we can see in the entire cycle of engine valves overlap 2 times i.e. closing of both valves during compression stroke and opening of both valves during exhaust stroke.

1.4 MAIN COMPONENTS OF SINGLE CYLINDER 4 STROKE DIESEL ENGINE 1. Engine block

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The engine block is made of nodular cast iron in one piece for all cylinder numbers. The main bearing caps are fixed from below by two hydraulically tensioned screws. They are guided sideways by the engine block at the top as well as at the bottom. Hydraulically tensioned horizontal side screws support the main bearing caps.

2. Crankshaft

The crankshaft is

forged in one piece.

Counterweights are

fitted on every web.

High degree of

balancing results in an

even and thick oil film for all bearings.

3. Connecting rod

The connecting rod of alloy steel is forged and machined with round sections. The lower end is split horizontally to allow removal of piston and connecting rod through the cylinder liner. All connecting rod bolts are hydraulically tightened. The gudgeon pin bearing is of tri-metal type. Oil is led to the gudgeon pin bearing and to the piston through a bore in the connecting rod.

4. Main bearings and big end bearings

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The big end bearings are of tri-metal type with steel back, lead bronze lining and a soft and thick running layer. Both tri-metal and bi-metal bearings are used as main bearings.

5. Cylinder liner

Centrifugally cast cylinder liner has a high and rigid collar to minimize deformations. The liner material is a special grey cast iron alloy developed for excellent wear resistance and high strength. Accurate temperature control is achieved with precisely positioned longitudinal cooling water bores. To eliminate the risk of bore polishing, the liner is equipped with an anti-polishing ring. The cooling water space between block and liner is sealed off by double O-rings. In the upper end the liner is equipped with an anti-polishing ring to eliminate bore polishing and reduce lube oil consumption. Fig: Cylinder liner & piston

6. Piston and piston rings

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The piston is of composite design with nodular cast iron skirt and steel crown. The piston skirt is pressure lubricated, which ensures a controlled oil distribution to the cylinder liner under all operating conditions. Oil is fed to cooling gallery in the piston top through the connecting rod. The piston ring grooves are hardened for good wear resistance. The piston ring set consists of two directional compression rings and one spring-loaded conformable oil scraper ring. All piston rings have wear resistant chromium plating.

7. Cylinder head

The cylinder head is designed for easy maintenance with only four hydraulically tightened studs. No valve cages are used, which results in very good flow dynamics in the exhaust gas channel. The exhaust valve seats are water cooled and all valves are equipped with valve rotators. The seat faces of the inlet valves are Satellite-plated. In case the engine is specified for MDF operation only, also the exhaust valves are Satellite-plated. Engines that are intended for operation on HFO have Mnemonic exhaust valves. 10 DEPT. OF MECHANICAL ENGINEERING 2018-19

CHAPTER -II

WORKING OF FOUR STROKE DIESEL ENGINE Diesel engine which is also known as compression ignition engine is widely used in automobile industries. Many big vehicles such as truck, bus, car etc. used diesel engine as the power unit because of its higher torque and greatermileage than petrol engine. Diesel engine is very popular in Indian market as well as in other countries because of lower price of diesel than petrol in many countries. So the requirement of diesel engine is much more than petrol engine. The ignition temperature of diesel is lower than petrol soothe working of diesel engine is slightly different than petrol engine. Working of Four Stroke Diesel Engine the power generation process in four stroke diesel engines is also divided into four parts. Each part is known as piston stroke. In IC engine, stroke is referred to the maximum distance travel by the piston in a single direction. The piston is free to move only in upward and downward direction. In four strokes engine the piston move two times up and down and the crankshaft move two complete revolutions to complete four piston cycles. The suction stroke, compression stroke, expansion stroke and exhaust stroke.

Suction stroke: In the suction stroke or intake stroke of diesel engine the piston start moves from top end of the cylinder to bottom end of the cylinder and simultaneously inlet valve opens. At this time air at atmospheric pressure drawn inside the cylinder through the 11 DEPT. OF MECHANICAL ENGINEERING 2018-19

inlet valve by a pump. The inlet valve remains open until the piston reaches the lower end of cylinder. After it inlet valve close and seal the upper end of the cylinder.

Compression stroke: After the piston passes bottom end of the cylinder, it starts moving up. Both valves are closed and the cylinder is sealed at that time. The piston moves upward. This movement of piston compresses the air into a small space between the top of the piston and cylinder head. The air is compressed into 1/22 or less of its original volume. Due to this compression a high pressure and temperature generate inside the cylinder. Both the inlet and exhaust valves do not open during any part of this stroke. At the end of compression stroke the piston is at top end of the cylinder.

Power stroke: At the end of the compression stroke when the piston is at top end of the cylinder a metered quantity of diesel is injected into the cylinder by the injector. The heat of compressed air ignites the diesel fuel and generates high pressure which pushes down the 12 DEPT. OF MECHANICAL ENGINEERING 2018-19

piston. The connection rod carries this force to the crankshaft which turns to move the vehicle. At the end of power stroke the piston reach the bottom end of cylinder.

Exhaust stroke: When the piston reaches the bottom end of cylinder after the power stroke, the exhaust valve opens. At this time the burn gases inside the cylinder so the cylinder pressure is slightly high from atmospheric pressure. This pressure difference allows burn gases to escape through the exhaust port and the piston move through the top end of the cylinder. At the end of exhaust all burn gases escape and exhaust valve closed. Now again intake valve open andthis process running until your vehicle starts.

CHAPTER-III

COMPONENTS OF 4 STROKE DIESEL ENGINE TEST RIG 13 DEPT. OF MECHANICAL ENGINEERING 2018-19

The test rig is designed to provide self-contained facility for teaching Internal Combustion (Compression Ignition) engine principles. The equipment is instrumented so that the following experiments could be performed.       

Bhp Measurement Ihp Measurement Fhp Measurement Fuel Consumption Measuement Air Intake Measurement Measurement Of Heat Rejected To Water Jacket Heat Balance Test

The engine test rig facilitate to evaluate the following 1. Performance at various throttle position 2. Heat Balance Sheet 3. Performance (BHP Measurement) from no load to full load

Description Two main components from main parts of the test rig. Welded steel base plate, complete with Dynamometer, drive shaft with safety guard, engine starting battery of 12V capacity and cooling water arrangement Panel board positioned over the base plate consisting of fuel system with flow measurement by burette, air flow measurement system, temperature and speed indicator

Dynamometer 1). The Dynamometer used is a Hydraulic Dynamometer capable of absorbing a maximum load of 10 HP at a speed of 1500 RPM 2). The Loading device used is an AC Alternator of matching capacity to load the engine up to 10 HP at 1500 RPM along with Resisistance loading arrangement for alternator. 3). The loading device used is an Eddy Current Dynamometer of matching capacity to load the engine up to 10 HP at 1500 RPM.

Instrumentation 1). The following instrumentation is provided. 2). Engine oil Pressure gauge 3). Engine charging circuit ammeter 14 DEPT. OF MECHANICAL ENGINEERING 2018-19

4). 'U' tube manometer for air flow rate 5). Burette for fuel flow rate 6). Digital Temperature Indicator- Multi point indicator with thermocouples. 7). Digital Voltmeter, Ammeter

Engine starting The test rig incorporates a 12 V DC electrical system designed for use with typical engine self starter system. The battery is included in the scope of supply.

Controls The test rig is arranged for manual control with Ignition switch for engine starting manual throttle control, manual control for hydraulic dynamometer loading and a manual operated clutch actuator arrangement to drive the engine with load or without load (For No Load testing)

Fuel measuring arrangement Fuel Measuring Arrangement consists of fuel tank, burette and suitable cock all mounted on a suitable framework and panel board and supplied with fuel piping from fuel tank to Engine.

Air intake measurement & heat carried away by exhaust gas Consisting of an air tank mounted on an iron stand fitted with a suitable orifice plate, manometer, Thermocouple for measuring the exhaust gas temperature with pocket connection with instruments suitably mounted on a panel board. Heat carried away by cooling water Consists of suitable inlet and outlet piping with flow control valve. Rota meter to measure the rate of flow of cooling water and Thermocouple with pocket connections for measuring inlet and outlet water temperature.

Services Electrical supply of 230V, Single Phase, 50Hz AC & external cooling water supply.

ADVANTAGES OF SINGLE CYLINDER 4 STROKE DIESEL ENGINE 15 DEPT. OF MECHANICAL ENGINEERING 2018-19

 The Diesel engine has the highest effective efficiency of all combustion engines.  Diesel engines inject the fuel directly into the combustion chamber, have no intake air restrictions apart from air filters and intake plumbing and have no intake manifold vacuum to add parasitic load and pumping losses resulting from the pistons being pulled downward against intake system vacuum. Cylinder filling with atmospheric air is aided and volumetric efficiency is increased for the same reason.  Although the fuel efficiency (mass burned per energy produced) of a Diesel engine drops at lower loads, it doesn't drop quite as fast as that of a typical petrol or turbine engine.[137] Diesel engines can combust a huge variety of fuels, including several fuel oils, that have advantages over fuels such as petrol. These advantages include:  Low fuel costs, as fuel oils are relatively cheap  Good lubrication properties  High energy density  Low risk of catching fire, as they do not form a flammable vapour  Biodiesel is an easily synthesised, non-petroleum-based fuel which can run directly in many Diesel engines, while gasoline engines either need adaptation to run synthetic fuels or else use them as an additive to gasoline (e.g., ethanol added to gasohol).  Diesel engines have a very good exhaust-emission behaviour. The exhaust contains minimal amounts of carbon monoxide and hydrocarbons. Direct injected Diesel engines emit approximately as much nitrogen oxide as Otto cycle engines. Swirl chamber and precombustion chamber injected engines, however, emit approximately 50 % less nitrogen oxide than Otto cycle engines when running under full load. [138]

Compared with Otto cycle engines, Diesel engines emit 10 times less pollutants

and 3 times less carbon dioxide.[139]  They have no high voltage electrical ignition system, resulting in high reliability and easy adaptation to damp environments. The absence of coils, spark plug wires, etc., 16 DEPT. OF MECHANICAL ENGINEERING 2018-19

also eliminates a source of radio frequency emissions which can interfere with navigation and communication equipment, which is especially important in marine and aircraft applications, and for preventing interference with radio telescopes. (For this reason, only Diesel-powered vehicles are allowed in parts of the American National Radio Quiet Zone.)[140]  Diesel engines can accept super- or turbocharging pressure without any natural limit, [141]

constrained only by the design and operating limits of engine components, such as

pressure, speed and load. This is unlike petrol engines, which inevitably suffer detonation at higher pressure if engine tuning and/or fuel octane adjustments are not made to compensate.

ASSEMBLY OF SINGLE CYLINDER 4 STROKE DIESEL ENGINE TEST RIG

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CHAPTER-IV STEPS TAKEN TO BUILD A SINGLE CYLINDER 4 STROKE DIESEL ENGINE

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CONVERSION PROCEDURE 1. Remove the cylinder head cover and identify the inlet valve, exhaust valve and piston of particular cylinder. 2. Mark the BDC and TDC position of flywheel this is done by rotating the crank in usual direction of rotation and observe the position of the fly wheel, when the piston is moving downwards at which the piston begins to move in opposite direction. I.e.from down to upward direction. Make the mark on the flywheel with reference to fixed point on the body of the engine. That point is the BDC for that cylinder .Measure the circumference. That point is TDC and is diametrically opposite to the BDC. 3. Insert the paper in the tappet clearance of both inlet and exhaust valves. 4. Slowly rotate the crank until the paper in the tappet clearance of inlet valve is gripped .make the mark on fly wheel against fixed reference. This position represent the inlet valve open (IVO). Measure the distance from TDC and tabulate the distance. 5. Rotate the crank further, till the paper is just free to move. Make the marking on the flywheel against the fixed reference. This position represents the inlet valve close (IVC). Measure the distance from BDC and tabulate the distance. 6. Rotate the crank further, till the paper in the tappet clearance of exhaust valve is gripped. Make the marking on the flywheel against fixed reference. This position represents the exhaust valve open (EVO). Measure the distance from BDC and tabulate. 19 DEPT. OF MECHANICAL ENGINEERING 2018-19

7. Then convert the measured distances into angle in degrees.

CHAPTER-V

DRAWING & PHOTOS 20 DEPT. OF MECHANICAL ENGINEERING 2018-19

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CHAPTER-VI

SAMPLE TEST READING

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SAMPLE TEST READING

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VALVE TIMING DIAGRAM Observation and Tabulation Circumference of the fly wheel =

Sl no.

1 2 3 4 5 6

Event

cm

Position of crankshaft with respect to TDC or BDC

Distance in “cm”

Angle in degrees

IVO IVC EVO EVC FVO FVS

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