Ashutoshgaurlisreport-180601193650.pdf

B.TECH.

STUDY OF LASER IGNITION SYSTEM A Project Report Submitted In Partial Fulfillment of the Requirements For the award of the Degree of

BACHELOR OF TECHNOLOGY in

STUDY OF LASER IGNITION SYSTEM

MECHANICAL ENGINEERING by

ASHUTOSH GAUR (1413240043) ARPIT SHARMA (1413240041) GAURAV TIWARI (1413240074) AVINASH K. SINGH (1413240047) ANUJ K. SINGH (1413240037) Under the supervision of

MR. VISHWAJEET RANJAN

DEPARTMENT OF MECHANICAL ENGINEERING

GREATER NOIDA INSTITUTE OF TECHNOLOGY Plot no. 7, Knowledge Park – II, Greater Noida, U.P(201310)

MAY 2018

Affiliated to Dr. A.P.J. Abdul Kalam Technical University, Lucknow, (Formerly Uttar Pradesh Technical University, Lucknow, U.P.) MAY, 2018

STUDY OF LASER IGNITION SYSTEM A Project Report Submitted In Partial Fulfillment of the Requirements For the award of the Degree of

BACHELOR OF TECHNOLOGY in

MECHANICAL ENGINEERING by

ASHUTOSH GAUR (1413240043) ARPIT SHARMA (1413240041) GAURAV TIWARI (1413240074) AVINASH K. SINGH (1413240047) ANUJ K. SINGH (1403240037)

Under the supervision of

Mr. VISHWAJEET RANJAN

DEPARTMENT OF MECHANICAL ENGINEERING

GREATER NOIDA INSTITUTE OF TECHNOLOGY, GREATER NOIDA Affiliated to Dr. A.P.J. Abdul Kalam Technical University, Lucknow (Formerly Uttar Pradesh Technical University, Lucknow, U.P.) MAY, 2018

GREATER NOIDA INSTITUTE OF TECHNOLOGY PLOT NO. 7, K.P. II, GREATER NOIDA, UP-201310 Affiliated to Dr. A.P.J. Abdul Kalam Technical University, Lucknow, UP (Formerly known as Uttar Pradesh Technical University, Lucknow)

CERTIFICATE This is to certify that project report entitled “STUDY OF LASER IGNITION SYSTEM” which is submitted by Ashutosh Gaur, Arpit Sharma, Gaurav Tiwari, Avinash k. Singh, Anuj K. Singh in partial fulfillment of the requirements for the award of degree Bachelor of Technology in Department of Mechanical Engineering from Greater Noida Institute of Technology, affiliated to Dr. A.P.J. Abdul Kalam Technical University, Lucknow is a record of the candidates own work carried out by them under my supervision. The matter embodied in this project report is original and has not been submitted for the award of any other degree.

(Mr. VISHWAJEET RANJAN) Supervisor

(Mr. ANUJ DIXIT) Project Co-ordinator Deptt.

(Dr. SUDHIR KUMAR) Prof. & HOD ME

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DECLARATION We hereby declare that this submission is our own work and that, to the best of our knowledge and belief. It contains no material previously published or written by another person nor material which to a substantial extent has been accepted for the award of any other degree or diploma of the university or other institute of higher learning, except where due acknowledgment has been made in the text.

Signature: Name: Ashutosh Gaur Roll no: 1413240043 Date: /05/2018

Signature: Name: Arpit Sharma Roll no: 1413240041 Date: /05/2018

Signature: Name: Gaurav Tiwari Roll no: 1413240074 Date: /05/2018

Signature: Name: Avinash k. Singh Roll no: 1413240047 Date: /05/2018

Signature: Name: Anuj K. Singh Roll no: 1413240037 Date: /05/2018

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ACKNOWLEDGEMENT It gives us a great sense of pleasure to present the report of B.Tech project undertaken during B.Tech. Final Year. We express our sincere gratitude to our respected supervisor, Mr. Vishwajeet Ranjan, (Assistant Professor, Department of Mechanical Engineering, Greater Noida Institute of Technology, Greater Noida) for his invaluable inspiring guidance and constant encouragement during the period of project work. We owe special debt of gratitude to Mr. Anuj Dixit (Assistant Professor, Department of Mechanical Engineering, Greater Noida Institute of Technology, Greater Noida) for his constant support and guidance throughout the course of our work. His sincerity, thoroughness and perseverance have been a constant source of inspiration for us. It is only his cognizant efforts that our endeavors have seen light of the day. We also take the opportunity to acknowledge the contribution of Professor Sudhir Kumar,

(Head, Department of Mechanical Engineering, Greater Noida Institute of Technology, Greater Noida) for his full support and assistance during the development of the project. We also like to acknowledge the contribution of all faculty members of the department for their kind assistance during the development of our project. Last but not the least, we acknowledge our friends for their contribution in the completion of this project.

Signature: Name: Ashutosh Gaur Roll no: 1413240043 Date: /05/2018

Signature: Name: Arpit Sharma Roll no: 1413240041 Date: /05/2018

Signature: Name: Gaurav Tiwari Roll no: 1413240074 Date: /05/2018

Signature: Name: Avinash k. Singh Roll no: 1413240047 Date: /05/2018

Signature: Name: Anuj K. Singh Roll no: 1413240037 Date: /05/2018 iv

ABSRACT With the advent of lasers in the 1960s, researcher and engineers discovered a new and powerful tool to investigate natural phenomena and improve technologically critical processes. Nowadays, applications of different lasers span quite broadly from diagnostics tools in science and engineering to biological and medical uses. In this report basic principles and applications of lasers for ignition of fuels are concisely reviewed from the engineering perspective. Recent progress in the area of high power fibre optics allowed convenient shielding and transmission of the laser light to the combustion chamber. However, issues related to immediate interfacing between the light and the chamber such as selection of appropriate window material and its possible fouling during the operation, shaping of the laser focus volume, and selection of spatially optimum ignition point remain amongst the important engineering design challenges. One of the potential advantages of the lasers lies in its flexibility to change the ignition location. Also, multiple ignition points can be achieved rather comfortably as compared to conventional electric ignition systems using spark plugs. Although the cost and packaging complexities of the laser ignition systems have dramatically reduced to an affordable level for many applications, they are still prohibitive for important and high-volume applications such as automotive engines. However, their penetration in some niche markets, such as large stationary power plants and military applications, are imminent. The laser ignition system burns air fuel mixture completely and runs the engine for a longer time compared to spark plug ignition system. It is help to achieving the best performance of vehicle. This project presents the overall scenario of the working of laser ignition system which as the name suggests makes use of the laser. In this paper, mostly considering performances of laser ignition and conventional spark ignition systems are comparatively evaluated in terms of in-cylinder pressure variation, combustion stability, fuel consumption, power output and exhaust emissions at similar operating conditions of the engine due to the better outcome of this project yet to be aimed it.

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LIST OF CONTENTS CERTIFICATE

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DECLARATION

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ACKNOWLEDGMENT

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ABSTRACT

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CONTENTS

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LIST OF FIGURE

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LIST OF TABLES

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LIST OF ABBREVIATIONS

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CHAPTER 1. INTRODUCTION 1.1 Introduction to Laser Ignition System

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1.2 Ignition

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1.3 Ignition types

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1.4 Spark Plug Ignition

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1.5 Limitation of Spark Ignition System

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CHAPTER 2. LASER 2.1 Solid State Laser (ND: YAG)

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CHAPTER 3. LITERATURE REVIEWS 3.1 Research Paper by Previous Scientist

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3.2 Gaps In Literature Review

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CHAPTER 4. LASER IGNITION SYSTEM 4.1 Principles of Laser Ignition System

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4.2 Laser ignition along time

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4.3 Ignition in combustion chamber

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4.4 Mechanism of laser ignition

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4.5 Arrangement of laser ignition system

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4.6 Working of laser ignition system

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4.7 Advantages of laser ignition system

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CHAPTER 5. PREVIOUS EXPERIMENTS AND RESULT

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CHAPTER 6. FUTURE RESEARCHES & APPLICATIONS 6.1 Future Researches

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6.2 Practical Laser Sparkplug Requirements

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6.3 Application

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CHAPTER 7. CONCLUSION

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REFRENCES

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LIST OF FIGURES Fig. No.

Figure Description

Figure 1

Spark Plug

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Figure 2

Four stroke engine cycle

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Figure 3

Different colour LASER

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Figure 4

ND : YAG laser

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Figure 5

Population Inversion

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Figure 6

Spontaneous Emission

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Figure 7

Stimulated Emission

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Figure 8

Optical breakdown in air generated

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Figure 9

Non Resonant Breakdown

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Figure 10

Stages of ignition with respect to time .

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Figure 11

Ignition inside combustion chamber

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Figure 12

Laser arrangement with respect to engine

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Figure 13

Focusing unit

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Figure 14

Laser Plug

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Figure 15

Working of LIS

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Figure 16

Arrangement of Laser Plug in cylinder head

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Figure 17

Layout Of Experiment

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Figure 18

Relation Between The IMEP And Equivalent Ratio

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Figure 19

Flame Kernel Development Of Laser And Spark Ignition

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Figure 20

Experimental setup for offline and online laser ignition

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Page No.

testing .

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Figure 21

Transmitted energy through the five optical plugs and

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subsequent plasmas produced Figure 22

Research Engine With The Q Switched ND : YAG Laser

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System Figure 23

Pressure Dependence On The Required Pulse Energy For

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Successful Ignition Figure 24

Comparison Of Fuel Consumption, Smoothness And

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Emissions Between Spark And Laser Ignition Figure 25

Spark Plug Ignition, Heavily Polluted On The Top And Self

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Cleansing Of Optical Window On Down Figure 26

Mazda RX 9 16X Rotar

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LIST OF TABLES Table No. Table 1

Table Description Specification of test engine Technical data of the research engine and the Nd:Yag laser

Table 2 Table 3

Page No. 28 32

used for the experiments 36

Potential requirements of LIS

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LIST OF ABBREVIATIONS Abbreviations ND: YAG

Full Form Neodymium-Doped Yttrium Aluminum Garnet

IMEP

Indicated Mean Effective Pressures

COV

Coefficient Of Variation

SIS

Spark Ignition System

LIS

Laser Ignition System

μs

Micro Second

mj

Milli-Joule

MPa

Mega Pascal

MPI

Multi Photon Ionization

DOHC

Double-Overhead-Camshaft

PPM

Particles Per Million

CH4

Methane

CO2

Carbon Dioxide

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CHAPTER 1 INTRODUCTION 1.1 Introduction to Laser Ignition System Since very long time, spark plugs have powered internal combustion engines. Located at the top of each engine cylinder, spark plugs send a high-voltage electrical spark across a gap between their two metal electrodes. That spark ignites the compressed air-fuel mixture in the cylinder, causing a controlled miniexplosion that pushes the piston down. One by product of the process is toxic nitrogen oxides (NOx), which pollute the air causing smog and acid rain. Engines would produce less NOx if they burnt more air and less fuel, but they would require the plugs to produce higher-energy sparks in order to do so. While this is technically possible, the voltages involved would burn out the electrodes quite quickly. Since lean mixtures have relatively slower flame speed than stoichiometric mixtures, any technique which may provide increase in the air–fuel mixture burning rate, would be beneficial. Flame speed in the lean burn SI engine can be increased either by generating turbulence in the cylinder or by shortening the flame travel distance for the same mixture strength. Reduction in flame travel path can be realized by employing multiple spark plugs in each cylinder or by placing the ignition point at an optimum location inside the combustion chamber. It is rather challenging to install multiple spark plugs in multi-cylinder engines because of already overcrowded cylinder head. Optimum spark location inside the combustion chamber is also difficult in case of conventional spark ignition systems because spark location is always very close to the top of combustion chamber. So the best solution for this is Laser Ignition System, in which we use laser igniters instead of conventional spark plug. Laser igniter ignite leaner mixtures without selfdestructing because they don't have electrodes. The operation of internal combustion engines with lean gas-air mixtures, laser igniters results in increase of fuel efficiencies and reduce green-house gas emissions by significant amounts.

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1.2 Ignition Ignition is the process of starting radical reactions until a self-sustaining flame has developed. One can distinguish between auto ignition, induced ignition and photoignition, the latter being caused by photolytic generation of radicals.

1.3 Ignition Types 1.3.1 Compression Ignition (CI) Or Auto Ignition At certain values of temperature and pressure a mixture will ignite spontaneously, this is known as the auto ignition or compression ignition. 1.3.2 Induced Ignition A process where a mixture, which would not ignite by it, is ignited locally by an ignition source (i.e. Electric spark plug, pulsed laser, microwave ignition source) is called induced ignition. In induced ignition, energy is deposited, leading to a temperature rise in a small volume of the mixture, where auto ignition takes place or the energy is used for the generation of radicals. In both cases subsequent flame propagation occurs and sets the mixture on fire. The process begins with multiphoton ionization of few gas molecules which releases electrons that readily absorb more photons via the inverse bremsstrahlung process to increase their kinetic energy. Electrons liberated by this means collide with other molecules and ionize them, leading to an electron avalanche, and breakdown of the gas. 1.3.3 Conventional Spark Plug A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine. A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator. The central electrode, which may contain a resistor, is connected by a heavily insulated wire to the output terminal of an ignition coil or magneto. The spark plug's metal shell is screwed into the engine's cylinder head and thus electrically grounded. The central electrode protrudes through the porcelain insulator into the combustion chamber, forming one or more 2

spark gaps between the inner end of the central electrode and usually one or more protuberances or structures attached to the inner end of the threaded shell and designated the side, earth, or ground electrode(s). Spark plugs may also be used for other purposes; in Saab Direct Ignition when they are not firing, spark plugs are used to measure ionization in the cylinders – this ionic current measurement is used to replace the ordinary cam phase sensor, knock sensor and misfire measurement function. Spark plugs may also be used in other applications such as furnaces wherein a combustible fuel/air mixture must be ignited. In this case, they are sometimes referred to as flame igniters.

Figure 1: Spark Plug

1.4 Spark Plug Ignition Conventional spark plug ignition has been used for many years. For ignition of a fuel-air mixture the fuel-air mixture is compressed and at the right moment a high voltage is applied to the electrodes of the spark plug. When the ignition switch is turned on current flows from the battery to the ignition coil. Current flows through the Primary winding of the ignition coil where one end is connected to the contact breaker. A cam which is directly connected to the camshaft opens and closes the contact breaker (CB) points according to the number of the cylinders. When the cam lobe Pushes CB switch, the CB point opens which causes the current from the primary circuit to break. Due to a break in the current, an EMF is induced in the second winding having more number of turns than the primary which increases the battery 12 volts to 22,000 volts. The high voltage produced by the secondary winding is then transferred to the 3

distributor. Higher voltage is then transferred to the spark plug terminal via a high tension cable. A voltage difference is generated between the central electrode and

Figure 2: Four stroke engine cycle

ground electrode of the spark plug. The voltage is continuously transferred through the central electrode (which is sealed using an insulator). When the voltage exceeds the dielectric of strength of the gases between the electrodes, the gases are ionized. Due to the ionization of gases, they become conductors and allow the current to flow through the gap and the spark is finally produced. In this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke (below). The combustion leads to the production of high pressure gases. Due to this tremendous force the piston is driven back to the bottom of the cylinder. As the piston moves downwards, the crankshaft rotates which rotates the wheels of the vehicle.

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1.5 Limitation of Spark Ignition System Location of spark plug is not flexible as it requires shielding of plug from immense heat and fuel spray. Ignition location cannot be chosen optimally. Spark plug electrodes can disturb the gas flow within the combustion chamber. It is not possible to ignite inside the fuel spray. It requires frequent maintenance to remove carbon deposits. Leaner mixtures cannot be burned, ratio between fuel and air has to be within the correct range. Degradation of electrodes at high pressure and temperature. Flame propagation is slow. Multi point fuel ignition is not feasible. Higher turbulence levels are required. Erosion of spark plug electrodes.

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CHAPTER 2 LASER LASER stands for Light Amplification by Stimulated Emission of Radiation. A laser is a device which produces highly directional light. It emits light through a process called stimulated emission of radiation which increases the intensity of light. A laser is different from conventional light sources in four ways: coherence, directionality, monochromatic, and high intensity. The light waves of ordinary light sources have many wavelengths. Hence, the photons emitted by ordinary light sources are out of phase. Thus, ordinary light is incoherent. On the other hand, the light waves of laser light have only one wavelength. Hence, all the photons emitted by laser light are in phase. Thus, laser light is coherent. The light waves from laser contain only one wavelength or color so it is known as monochromatic light. The laser beam is very narrow and can be concentrated on a very small area. This makes laser light highly directional. The laser light spreads in a small region of space. Hence, all the energy is concentrated on a narrow region. Therefore, laser light has greater intensity than the ordinary light. Einstein gave the theoretical basis for the development of laser in 1917, when he predicted the possibility of stimulated emission. In 1954, C.H. Townes and his co-workers put Einstein’s prediction for practical realization. They developed a microwave amplifier based on stimulated emission of radiation. It was called as MASER (Microwave Amplification by Stimulated Emission of Radiation. Maser operates on principles similar to laser but generates microwaves rather than light radiation. In 1958, C.H. Townes and A. Schawlow extended the principle of masers to light. In 1960, T.H. Maiman built the first laser device. Lasers are classified into 4 types based on the type of laser medium used: Solid-state laser Gas laser Liquid laser Semiconductor laser 6

Figure 3: Different color LASER

2.1 (ND: YAG) Solid State Laser Neodymium-doped Yttrium Aluminum Garnet (ND: YAG) laser is a solid state laser in which ND: YAG is used as a laser medium. These lasers have many different applications in the medical and scientific field for processes such as Lasik surgery and laser spectroscopy. ND: YAG laser is a four-level laser system, which means that the four energy levels are involved in laser action. These lasers operate in both pulsed and continuous mode. ND: YAG laser generates laser light commonly in the near-infrared region of the spectrum at 1064 nanometers (nm). It also emits laser light at several different wavelengths including 1440 nm, 1320 nm, 1120 nm, and 940 nm. 2.1.1 Nd: Yag Laser Construction Nd: YAG laser consists of three important elements: an energy source, active medium, and optical resonator. 2.1.1.1 Energy Source The energy source or pump source supplies energy to the active medium to achieve population inversion. In Nd: YAG laser, light energy sources such as flashtube or laser diodes are used as energy source to supply energy to the active medium. In the past, flashtubes are mostly used as pump source because of its low cost. However, nowadays, laser diodes are preferred over flashtubes because of its high efficiency and low cost.

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Figure 4: ND: YAG laser[16]

2.1.1.2 Active Medium The active medium or laser medium of the Nd:YAG laser is made up of a synthetic crystalline material (Yttrium Aluminum Garnet (YAG)) doped with a chemical element (neodymium (Nd)). The lower energy state electrons of the neodymium ions are excited to the higher energy state to provide lasing action in the active medium. 2.1.1.3 Optical Resonator The Nd:YAG crystal is placed between two mirrors. These two mirrors are optically coated or silvered. Each mirror is silvered or coated differently. One mirror is fully silvered whereas, another mirror is partially silvered. The mirror, which is fully silvered, will completely reflect the light and is known as fully reflecting mirror. On the other hand, the mirror which is partially silvered will reflect most part of the light but allows a small portion of light through it to produce the laser beam. This mirror is known as a partially reflecting mirror.

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2.1.2 Working of Nd:Yag Laser Nd: YAG laser is a four-level laser system, which means that the four energy levels are involved in laser action. The light energy sources such as flashtubes or laser diodes are used to supply energy to the active medium. In Nd:YAG laser, the lower energy state electrons in the neodymium ions are excited to the higher energy state to achieve population inversion. Consider a Nd:YAG crystal active medium consisting of four energy levels E1, E2, E3, and E4 with N number of electrons. The number of electrons in the energy states E1, E2, E3, and E4 will be N1, N2, N3, and N4. Let us assume that the energy levels will be E1 < E2 <E3 <E4. The energy level E1 is known as ground state, E2 is the next higher energy state or excited state, E3 is the metastable state or excited state and E4 is the pump state or excited state. Let us assume that initially, the population will be N1 > N2 > N3 > N4. When flashtube or laser diode supplies light energy to the active medium (Nd:YAG crystal), the lower energy state (E1) electrons in the neodymium ions gains enough energy and moves to the pump state or higher energy state E4.

Figure 5: Population Inversion[16]

The lifetime of pump state or higher energy state E4 is very small (230 microseconds (µs)) so the electrons in the energy state E4 do not stay for long period. After a short period, the electrons will fall into the next lower energy state or metastable state E3 by releasing non-radiation energy (releasing energy without emitting photons). The lifetime of metastable state E3 is high as compared to the lifetime of pump state E4. Therefore, the electrons reach E3 much faster than they leave E3. This 9

results in an increase in the number of electrons in the metastable E3 and hence population inversion is achieved. After some period, the electrons in the metastable state E3 will fall into the next lower energy state E2 by releasing photons or light. The emission of photons in this manner is called spontaneous emission.

Figure 6: Spontaneous Emission[16]

The lifetime of energy state E2 is very small just like the energy state E4. Therefore, after a short period, the electrons in the energy state E2 will fall back to the ground state E1 by releasing radiation less energy. When photon emitted due to spontaneous emission is interacted with the other metastable state electron, it stimulates that electron and makes it fall into the lower energy state by releasing the photon. As a result, two photons are released. The emission of photons in this manner is called stimulated emission of radiation.

Figure 7: Stimulated Emission[16]

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When these two photons again interacted with the metastable state electrons, four photons are released. Likewise, millions of photons are emitted. Thus, optical gain is achieved. Spontaneous emission is a natural process but stimulated emission is not a natural process. To achieve stimulated emission, we need to supply external photons or light to the active medium. The Nd:YAG active medium generates photons or light due to spontaneous emission. The light or photons generated in the active medium will bounce back and forth between the two mirrors. This stimulates other electrons to fall into the lower energy state by releasing photons or light. Likewise, millions of electrons are stimulated to emit photons. The light generated within the active medium is reflected many times between the mirrors before it escapes through the partially reflecting mirror. Advantages of Nd:YAG laser Low power consumption Nd:YAG laser offers high gain. Nd:YAG laser has good thermal properties. Nd:YAG laser has good mechanical properties. The efficiency of Nd:YAG laser is very high as compared to the ruby laser.

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CHAPTER 3 LITERATURE REVIEW 3.1 Research Paper by Previous Scientist Mantri, H, and Ramtek, M [1] (2016), examine the various positions of laser igniter and plot the performance graph showing the comparison of laser ignition and spark ignition and he founds that the brake thermal efficiency and indicated power are increases in engine with laser ignition system than the spark ignition system in engine. This system can work even in high compression ratio, compression rates, high temperature and high pressure. Specific fuel consumption decreases in the laser ignition system as laser ignition system can operate on lean mixtures. The significant reduction in combustion time and better time control can be achieved by using multipoint laser ignition system. Kothari, Modasara, A, et.al, [2] (2016), discusses the potential advantages and control opportunities and considers the challenges faced, construction and working of laser ignitor and the system requirements for laser ignitor. In order to generate the laser Nd: YAG is chosen as laser active medium emitting at λem = 1064 nm, and Cr: YAG as passive saturable absorber. There are four different ways in which laser light can interact with a combustible mixture to initiate an ignition event namely, Thermal initiation, Non resonant breakdown, Resonant breakdown, and Photochemical ignition. Out of the above stated different ways non resonant breakdown is more frequently used because of its freedom in selecting the laser wavelength and ease of implementation. At present the laser ignition plug is very expensive and commercially not yet available. They also explain types of laser ignition system and working of laser ignition system. Saxena, A. [3] (2015), described that how a revolutionary change has come after the positive research work on laser igniters which can replace the conventional spark plug in near future very soon. This replacement of conventional spark plugs to laser igniters will be a milestone in automobile industry. Laser igniters will be able to combust the fuel with lean air-fuel mixture as compare to conventional spark plug, which helps to lower down the Nox emission and gives better fuel 12

efficiency and a better clean environment. Harel.S, Sonawane.V et.al, [5] (2014), The thermodynamic requirements of a high compression ratio and a high power density are fulfilled well by laser ignition. Through this paper, the objective is to present the current state of the relevant knowledge on fuel ignition and discuss selected applications, advantages, in the context of combustion engines. Sustainability with regard to internal combustion engines is strongly linked to the fuels burnt and the overall efficiency. Laser ignition can enhance the combustion process and minimize pollutant formation. This paper is on laser ignition of sustainable fuels for future internal combustion engines. Ignition is the process of starting radical reactions until a self-sustaining flame has developed. In technical appliances such as internal combustion engines, reliable ignition is necessary for adequate system performance. Ignition strongly affects the formation of pollutants and the extent of fuel conversion. Laser ignition system can be a reliable way to achieve this. They show how does laser light can interact with a combustible mixture to initiate an ignition event. In the end they have discussed some experimental results regarding measurements of fuel consumption and emissions which prove that laser ignition has important advantages compared to conventional spark ignition systems. Sharma.V, [6] (2014), Assistant professor of mechanical engineering department has proposed the use of CNG in the IC engine, and found the drastic reduction in the emission to the environment by the use of CNG in the engine and as we know that the CNG plays a dominating role the transport and energy production. Unfortunately, the spark plug cannot ignite the leaner mixture of fuel and air for the longer time and also it produces exhaust emission and results in the reduction of the efficiency of the engine and also reduces the NOx concentration in the exhaust gas. Vikas Sharma has also explained the concept of ignition of the combustibles, in CNG engine as the ignition of a combustible requires a high voltage is applied to the electrodes of the spark plug. Mullett, J. D, Dodd, R, et al [7] (2006), in this paper they tell us the four principles of laser ignition system that are, Non resonant Breakdown Ignition, Resonant 13

Breakdown, Thermal initiation, Photochemical ignition. In this paper the investigate the effects of laser parameter on LIS and the performance of LIS against SI. It works on the principle of Non resonant breakdown principle in which begins with the multiphoton ionisation of a few molecules in release of electron takes place and thus is absorbed by laser head. After which an avalanche is created and through which the kinetic energy of other molecule increases and thus breakdown occur. Through this experiment the main focus is to reduce the energy required to ignite the molecules when compared with SI ignitors and thus graph is plotted between energies and found that energy of 4mJ. The experiment was conducted in two modes first is offline and second was online. Result were drawn out through graph mode from energy meter through offline mode in which laser before entering the optical plug and existing through is plotted. In online mode the laser is passed through engine and calculation takes place through optical plug. M. Lackner, F. Winter, et al [8] (2006), In this paper laser-induced ignition of hydrogen/air and biogas/air mixtures was investigated experimentally in a static combustion bomb. The whole experiment was done with two modes in first, plane window was inserted into the cylinder head of the engine. A focusing lens was placed in front of that window in order to focus the laser beam down into the combustion bomb called as “separate optics”. And in second mode, lens like curvature was engraved directly into the window. By using such a special window, no further lens was required called as “combined optics”. Schlieren photography was applied to get information on the shock wave propagation and early flame kernel development. In this paper it was found for the laser ignition tests with hydrogen that with higher initial pressures the minimum pulse energy for ignition (MPE) decreases. And secondly the work on the self-cleansing property of optical window.

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J. D. Dale et.al.[9] (2008), In his study, the use of laser ignition to improve gas engine performance was initially demonstrated by J. D. Dale in 1978. However, with very few exceptions, work in this area has for the last 20 years been limited to laboratory experimentation employing large, expensive and relatively complicated lasers and laser beam delivery systems. Experimental studies have been vital to extending the value of the theoretical examinations and in gaining a further understanding of the combustion process. Experimental studies have been vital to extending the value of the theoretical examinations and in gaining a further understanding of the combustion process. Combustion vessel and open flame jet experimentation with methane (CH4) and other combustible gases have proven invaluable in the search for better fuel economy and emissions and provide a better understanding of the general ignition and combustion processes. A.P. Yalin, M. Miyagi et.al [18] (2008) In his study This performed experiments to determine misfire limit and knock limit of LI system. They reported increased misfire limit, and decreased ignition delay for LI compared to SI engine. In the past, lasers that could meet those requirements were limited to basic research because they were big, inefficient, and unstable. Nor could they be located away from the engine, because their powerful beams would destroy any optical fibers that delivered light to the cylinders. This problem overcame by making composite lasers from ceramic powders. In this the powder is heated and fuse into optically transparent solids and embeds metal ions in them to tune their properties. Ceramics are easier to tune optically than conventional crystals. They are also much stronger, more durable, and thermally conductive, so they can dissipate the heat from an engine without breaking down.

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3.2 GAPS IN LITERATURE REVIEW After reading above mentioned research /review papers we find some areas where we can proceed our study because researches in these fields are still in progress that makes our study feasible and we can complete our domain on some of the points mentioned below, Since the cost of this system is high so we can do some studies on reducing the initial cost of the laser ignition system so that it can be implemented on commercial level. Multi Point ignition technique can be achieved by proposing a single-shot laser and we can test its feasibility. We can get the advantage of rapid combustion We can study the position of laser ignitor in the IC engine. We can do research and study in improving the combustion stability by which we can enable engine to be run under leaner condition with exhaust gas recirculation(EGR) concentration, or at lower idle speed without increasing noise, vibrations and harshness characteristics of the vehicles. We might go under further studies in development of higher average power and higher pulse frequency lasers, it is expected that a multi-strike laser ignition system an associate combustion can reduce the probability of misfires under high levels of dilutions. We can do some studies for the stability and self-cleaning of optical window of laser ignition system.

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CHAPTER 4 LASER IGNITION SYSTEM Laser ignition, or laser-induced ignition, is the process of starting combustion by the stimulus of a laser light source. Laser ignition uses an optical breakdown of gas molecule caused by an intense laser pulse to ignite gas mixtures. The beam of a powerful short pulse laser is focused by a lens into a combustion chamber and near the focal spot and hot and bright plasma is generated

Figure 8: Optical breakdown in air generated by a ND: YAG laser.

The process begins with multi-photon ionization of few gas molecules which releases electrons that readily absorb more photons via the inverse bremsstrahlung process to increase their kinetic energy. Electrons liberated by this means collide with other molecules and ionize them, leading to an electron avalanche, and breakdown of the gas. Multi photon absorption processes are usually essential for the initial stage of breakdown because the available photon energy at visible and near IR wavelengths is much smaller than the ionization energy. For very short pulse duration (few picoseconds) the multi photon processes alone must provide breakdown, since there is insufficient time for electron-molecule collision to occur. Thus this avalanche of electrons and resultant ions collide with each other producing immense heat hence creating plasma which is sufficiently strong to ignite the fuel. The wavelength of laser depends upon the absorption properties of the laser and the minimum energy required depends upon the number of photons required for producing the electron avalanche.

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4.1 Principles of Laser Ignition System 4.1.1 Thermal Initiation In thermal initiation of ignition, there is no electrical breakdown of the gas and a laser beam is used to raise the kinetic energy of target molecules in translational, rotational, or vibrational forms. Consequently, molecular bonds are broken and chemical reaction occur leading to ignition with typically long ignition delay times. This method is suitable for fuel/oxidizer mixtures with strong absorption at the laser wavelength. However, if in a gaseous or liquid mixtures is an objective, thermal ignition is unlikely a preferred choice due to energy absorption along the laser propagation direction. Conversely, this is an ideal method for homogeneous or distributed ignition of combustible gases or liquids. Thermal ignition method has been used successfully for solid fuels due to their absorption ability at infrared wavelengths. 4.1.2 Non-Resonant Breakdown In non-resonant breakdown ignition method, because typically the light photon energy is invisible or UV range of spectrum, multi photon processes are required for molecular ionization. This is due to the lower photon energy in this range of wavelengths in comparison to the molecular ionization energy. The electrons thus freed will absorb more energy to boost their kinetic energy (KE), facilitating further molecular ionization through collision with other molecules. This process shortly leads to an electron avalanche and ends with gas breakdown and ignition. By far, the most commonly used technique is the non-resonant initiation of ignition primarily because of the freedom in selection of the laser wavelength and ease of implementation.

Figure 9: Non Resonant Breakdown

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Resonant breakdown The resonant breakdown laser ignition process involves, first, a non-resonant multi photon dissociation of molecules resulting to freed atoms, followed by a resonant photo ionization of these atoms. This process generates sufficient electrons needed for gas breakdown. Theoretically, less input energy is required due to the resonant nature of this method. 4.1.3 Photochemical Mechanisms In photochemical ignition approach, very little direct heating takes place and the laser beam brings about molecular dissociation leading to formation of radicals (i.e., highly reactive chemical species), if the production rate of the radicals produced by this approach is higher than the recombination rate (i.e., neutralizing the radicals), then the number of these highly active species will reach a threshold value, leading to an ignition event. This (radical) number augmentation scenario is named as chain branching in chemical terms.

4.2 Laser Ignition Along Time Laser ignition encompasses the nanosecond domain of the laser pulse itself to the duration of the entire combustion lasting several hundreds of milliseconds.

Figure 10: Stages of ignition with respect to time[8]

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The laser energy is deposited in a few nanoseconds which lead to a shock wave generation. In the first milliseconds an ignition delay can be observed which has duration between 5 – 100 ms depending on the mixture. Combustion can last between 100 ms up to several seconds again depending on the gas mixture, initial pressure, pulse energy, plasma size, position of the plasma in the combustion bomb and initial temperature.

4.3 Ignition in Combustion Chamber The laser beam is passed through a convex lens, this convex lens diverges the beam and make it immensely strong and sufficient enough to start combustion at that point. Hence the fuel is ignited, at the focal point. The focal point is adjusted where the ignition is required to have. To provide more understanding of laser ignition, also for higher initial temperatures than 200°C provided by the combustion chamber 1, a new combustion chamber which can be heated up to maximum temperatures of 400°C was constructed (combustion chamber 2). Higher initial temperatures are also interesting because they are nearer to engine like conditions.

Figure 11: Ignition inside combustion chamber

4.4 Mechanism of Laser Ignition It is well known that short and intensive laser pulses are able to produce an “optical breakdown” in air. Necessary intensities are in the range between 1010 to 1011W/cm2. At such intensities, gas molecules are dissociated and ionized within the vicinity of the focal spot of a laser beam and hot plasma is generated. This plasma is heated by the incoming laser beam and a strong shock wave occurs. The 20

expanding hot plasma can be used for the ignition of fuel-gas mixtures. By comparing the field strength of the field between the electrodes of a spark plug and the field of a laser pulse it should be possible to estimate the required laser intensity for generation of an optical breakdown.

The field strength reaches

values in the range of approximately 3×104V/cm between the electrodes of a conventional spark plug. Since the intensity of an electromagnetic wave is proportional to the square of the electric field strength, one can estimate that the intensity should be in the order of 2 × 106 W/ cm2 which is several orders of magnitude lower as indicated by experiments on laser ignition. The reason is that usually no free electrons are available within the irradiated volume. At the electrodes of a spark plug electrons can be liberated by field emission processes. In contrary, ionization due to irradiation requires a “multi photon” process where several photons hit the atom at nearly the same time. Such multi photon ionization processes can only happen at very high irradiation levels (in the order of 1010to 1011W/ cm2.) where the number of photons is extremely high. For example, nitrogen has an ionization energy of approximately 14.5 eV, whereas one photon emitted by a Nd: YAG laser has an energy of 1.1 eV, thus more than 13 photons are required for ionization of nitrogen. The pulse energy of a laser system for ignition can be estimated by the following calculation. The diameter d of a focused laser beam is (D = 2 × wf × M2 × 2λf πd) where M2 is the beam quality, F is the focal length of the optical element and D is the diameter of the laser beam with the wavelength λ. Now it is assumed that the laser beam irradiates a spherical volume. From the thermodynamic gas equation, the number of particles N in a volume V is,(V = 4πw3) , (N = pv kt ) With the pressure p, temperature T and Boltzmann’s constant k = 1.38 × 10 23J/K. Inside the irradiated volume, N molecules have to be dissociated where first the dissociation energy Wd is required and finally 2N atoms are ionized (ionization energy Wi). Using known values for Wd= 9.79 eV and Wi= 14.53 eV for nitrogen, the energy for dissociating and ionizing all particles inside the volume can be calculated as W = (πpd3 6kt) × (Wd + 2Wi) For a spot radius of about 100 μm the equation gives a maximum energy of approximately 1 mJ. 21

Since not all particles inside the irradiated volume have to be ionized, even smaller energies should be sufficient for generation of an optical breakdown. It is assumed that the intensity which is necessary for the generation of an optical breakdown processes is related to the pressure of the gas I α 1/Pn with n =1…5 depending on the mechanism of multi photon process. Higher pressures, like in a combustion chamber should ease the ignition process what favors the laser induced ignition.

4.5 Arrangement of Laser Ignition System A laser ignition device for irradiating and condensing laser beams in a combustion chamber of an internal combustion engine so as to ignite fuel particles within the combustion chamber, includes: a laser beam generating unit for emitting the laser beams; and a condensing optical member for guiding the laser beams into the combustion chamber such that the laser beams are condensed in the combustion chamber.

Figure 12: Laser arrangement with respect to engine.[6]

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4.5.1 Power Source The average power requirements for a laser spark plug are relatively modest. A four stroke engine operating at maximum of 1200 rpm requires an ignition spark 10 times per second or 10Hz (1200rpm/2x60). For example, 1-Joule/pulse electrical diode pumping levels we are readily able to generate high mill joule levels of Q-switched energy. This provides us with an average power requirement for the laser spark plug of say approximately 1-Joule times 10Hz equal to approximately 10 Watts. 4.5.2 Combustion Chamber Window Since the laser ignition system is located outside the combustion chamber a window is required to optically couple the laser beam. The window must: a) Withstand the thermal and mechanical stresses from the engine. b) Withstand the high laser power. c) Exhibit low propensity to fouling. 4.5.3 Optic Fiber Wire It is used to transport the laser beam from generating unit to the focusing unit. 4.5.4 Focusing Unit A set of optical lenses are used to focus the laser beam into the combustion chamber. The focal length of the lenses can be varied according to where ignition is required. The lenses used may be either combined or separated.

Figure 13: Focusing unit

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4.5.5 Laser Plug Located at the top of each engine cylinder, spark plugs send a high-voltage electrical power to plasma. That plasma spark ignites the compressed air-fuel mixture in the cylinder, causing a controlled mini-explosion that pushes the piston down. Additionally, engine timing could be improved, as lasers can pulse within nanoseconds, while spark plugs require milli-seconds. In order to cause the desired combustion, a laser would have to be able to focus light to approximately 100 giga-watts per square centimeter with short pulses of more than 10 millijoules each. Previously, that sort of performance could only be achieved by large, inefficient, relatively unstable lasers. The Japanese researchers, however, have created a small, robust and efficient laser that can do the job. They did so by heating ceramic powders, fusing them into optically-transparent solids, then embedding them with metal ions in order to tune their properties.

Figure 14: Laser Plug

4.6 Working of Laser Ignition System The laser ignition system has a laser transmitter with a fibre-optic cable powered by the car’s battery. The average power requirements for a laser spark plug are relatively modest. A four stroke engine operating at maximum of 1200 rpm requires an ignition spark 10 times per second or 10Hz (1200rpm/2x60). For example, 1-Joule/pulse electrical diode pumping levels we are readily able to generate high mill joule levels of Q-switched energy. This provides us with an average power requirement for the laser spark plug of say approximately 1-Joule times 10Hz equal to approximately 10 Watts. It shoots the laser beam to a 24

focusing lens that would consume a much smaller space than current spark plugs. The lenses focus the beams into an intense pinpoint of light by passing through an optical window. The laser beam is passed through a convex lens, this convex lens diverges the beam and make it immensely strong and sufficient enough to start combustion at that point. Hence the fuel is ignited, at the focal point, with the mechanism shown above. The focal point is adjusted where the ignition is required to have. when the fuel is injected into the engine, the laser is fired and produces enough energy (heat) to ignite the fuel.

Hence the fuel is ignited, at the focal point, with the

mechanism shown above. The focal point is adjusted where the ignition is required to have. The plasma generated by the Laser beam results in two of the following actions: 1. Emission of high energy photons 2. Generation of shock waves The high energy photons, heat and ionize the charge present in the path of laser beam which can be seen from the propagation of the flame which propagates longitudinally along the laser beam. 3.The shock waves carry energy out wards from the laser beam and thus help in propagation of flame. If the electrons gain sufficient energy, they can ionize other gas molecules on impact, leading to an electron cascade and breakdown of the gas in the focal region.

Figure 15: Working of LIS

It is important to note that this process requires initial seed electrons. These electrons are produced from impurities in the gas mixture (dust, aerosols and soot particles) which are always present. These impurities absorb the laser radiation and lead to high local temperature and in consequence to free electrons starting the 25

avalanche process. In contrast to multi photon ionization (MPI), no wavelength dependence is expected for this initiation path. The minimum ignition energy required for laser ignition is more than that for electric spark ignition because of following reasons: An initial comparison is useful for establishing the model requirements, and for identifying causes of the higher laser MIE. First, the volume of a typical electrical ignition spark is 103 cm3. The focal volume for a typical laser spark is 10-5 cm3 Since atmospheric air contains 1000 charged particles/cm3, the probability of finding a charged particle in the discharge volume is very low for a laser spark. Second, an electrical discharge is part of an external circuit that controls the power input, which may last milliseconds, although high power input to ignition sparks is usually designed to last < 100 ns. Breakdown and heating of laser sparks depend only on the gas, optical, and laser parameters, while the energy balance of spark discharges depends on the circuit, gas, and electrode characteristics. The efficiency of energy transfer to near-threshold laser sparks is substantially lower than to electrical sparks, so more power is required to heat laser sparks. Another reason is that, energy in the form of photons is wasted before the beam reach the focal point. Hence heating and ionizing the charge present in the path of laser beam.

Figure 16: Arrangement of Laser Plug in cylinder head

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This can also be seen from the propagation of flame which propagates longitudinally along the laser beam. Hence this loss of photons is another reason for higher minimum energy required for laser ignition than that for electric spark.

4.7 Advantages of Laser Ignition The main advantages of laser ignitions are given below: A choice of arbitrary positioning of the ignition plasma in the combustion cylinder. Absence of quenching effects by the spark plug electrodes. Ignition of leaner mixtures than with the spark plug; lower combustion temperatures and less NOx emissions. No erosion effects as in the case of the spark plugs, lifetime of a laser ignition System expected to be significantly longer than that of a spark plug. High load/ignition pressures possible, increasing efficiency. Precise ignition timing possible. Exact regulation of the ignition energy deposited in the ignition plasma. Easier possibility of multipoint ignition. Shorter ignition delay time and shorter combustion time. The thermodynamic requirements of a high compression ratio and a high power density are fulfilled well by laser ignition.

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CHAPTER 5 PREVIOUS EXPERIMENTS AND RESULT 1.

The experiment was done for the development of unconventional natural gas resources. Achieving lean burn with supercharging to attain high thermal efficiencies with the help of laser igniters. The engine specification and setup is shown below in table number 1, Table 1: Specification Of Test Engine[11]

Base Engine

NFD170

Bore*stroke

102*105

Displacement

857(cm3)

Compression Ratio

12,14

Fuel

Methane

Rotational Speed

1200

Ignition Timing

MBT

Maximum Pressure

8

Figure 17: Layout Of Experiment[11]

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The main result of the demonstration is the relation between the Indicated Mean Effective Pressure(IMEP) and the equivalence ratio, is shown in figure 18. The horizontal axis represents the equivalence ratio and the left side of the figure is leaner. The side corresponds to the output from the engine. The spark and the laser ignition results are represented by the square and circle points, respectively. Data in normal aspiration. Without supercharging, are indicated as hollow characters, and the color which are listed in the figure, represents the intake pressure. For normal aspiration experiments, the laser maintained higher IMEP compared to the spark plug ignition. Then for the case of supercharging, spark plugs that are represented as red squares rapidly shifted towards rich side. This indicates that spark plugs cannot ignite for the pre-mixture under high-pressure conditions. On the other hand, it has been demonstrated that laser can maintain stable ignition even in the supercharged condition up to an intake pressure of 1.8 atm, which is the limit of the engine system.

Figure 18: Relation Between The IMEP And Equivalent Ratio[11]

Both LIS and SPI utilizes hot plasma but the physics behind the formation of both sources is different and we take that benefit.

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Figure 19: Flame Kernel Development Of Laser And Spark Ignition[11]

The LIS works in two phases first the laser ionizes the molecules and discharge the electrons and then secondly the electron absorbs the laser energy through inverse BREMESTRAHLUNG process. Fig19 shows the propagation of flame kernel in LIS and SPI. 2. The below experiment was conducted at University of Liverpool and laser used for the LI experiments was a ‘Mini-Q’ Q-switched Nd:YAG, manufactured by GSI Group, operating at the fundamental wavelength of 1064 nm. Five different focal length (FL) lenses (15, 18, 24, 30 and 36 mm) were tested individually in a specifically designed optical plug. These were all uncoated BK7 Plano-convex lenses, apart from the 36 mm FL lens, which had a visible to near infrared coating. An uncoated sapphire window was sealed at the bottom of the optical plug for each of these different lenses.

Figure 20: Experimental setup for offline and online laser ignition testing.[7]

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The minimum beam waist produced by each lens was positioned at 4 mm from the bottom of the plug (which is at the same location as the electrical discharge of the spark plugs), as this was found from previous testing to be the optimum LI position for this engine. Mirror (1) was installed on the optical bench for offline testing to direct the beam into the optical plug, as shown in figure 20.

Figure 21: Transmitted energy through the five optical plugs and subsequent plasmas produced[7]

The offline results for increasing the pulse energy into the five optical plugs are illustrated in fig.21, which shows the transmitted energies through the plugs. The peak of each curve indicates the minimum energy required to cause optical air breakdown at atmospheric pressure for the respective FL lenses. After this point, plasmas were formed which absorbed the incident energy. It can be seen from figure 2 that at the higher plasma producing input energies, the transmitted energy through the optical plugs and plasma becomes fairly constant, which indicates that a percentage of the incident energy is being absorbed by the plasma. The lowest minimum laser energy required for misfire free combustion was found to be 4 mJ per pulse, also using the 15 mm FL lens in the optical plug. This compares to ~30 mJ in a ~1 ms electrical pulse for conventional SI. The minimum laser irradiance required for LI was found to reduce when longer FL lenses were used, and improved combustion performance and stability was achieved by using higher laser energies.

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3. A laser ignition system has been used for ignition of an internal combustion engine. Since results have already been published, only a brief overview is given here. Table 2: Technical data of the research engine and the ND: YAG laser used for the experiments.[6]

Technical data of the research engine and the laser used for the experiments are summarized in table2.

Figure 22: Research Engine With The Q-Switched Nd: Yag Laser System[6]

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The experimental setup is shown in fig. 22. Measurements on the dependence of the pressure on the required pulse energy for ignition are summarized in fig.23.

Figure 23: Pressure Dependence On The Required Pulse Energy For Successful Ignition.[6]

Results indicate that the required pulse energy for successful ignition decreases with increasing pressure.

Figure 24: Comparison Of Fuel Consumption, Smoothness And Emissions Between Spark And Laser Ignition[1][6]

Results on consumption measurements are summarized in fig.24. Compared to conventional spark plug ignition, laser ignition, laser ignition reduces the fuel 33

consumption by several per cents. Exhaust emissions are reduced by nearly 10%. Additionally, a frequency-doubled Nd:YAG laser has been used to examine possible influences of the wavelength on the laser ignition process. No influences on the required pulse energy for successful ignition could be found. Fig.25 shows the images of combustor taken by photography after the testing of almost 20hrs.

Figure 25: Spark plug ignition, heavily polluted on the left and self-cleansing of optical window on right.[6]

It is observed that the optical window of laser plug cleans itself after several cycles and so there is no suet deposition and whereas the spark plug is heavily polluted after several hour running of engine.

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CHAPTER 6 FUTURE RESEARCHES & APPLICATIONS 6.1 Future Researches Delivering the beam through free space and channeling it into the combustion chamber through the optical plug achieved the best results – reducing the Coefficient of Variation, making combustion smoother and more fuel efficient. The team was particularly keen to deliver the beam via optical fiber, since this was likely to be less susceptible to engine vibration and could facilitate improved engine layout. They tried out a range of optical fibers, including silica and sapphire, and experimented with different internal fiber structures, core sizes and beam coupling optics. Delivering the beam via optical fiber proved to be more difficult than the research team had hoped. The fiber didn’t respond well to engine vibration, which increased the divergence of the output beam and reduced the beam mode quality. Bending the fiber was also problematical and up to 20 per cent of the beam energy was lost with small bend diameters, while tight bends caused the fiber to fail altogether after a period. What’s more, the high density of laser energy can cause immediate or long term degradation, leading to loss of beam transmission and therefore loss of ignition. Careful design of laser parameters, fiber coupling and choice of optical media is crucial to avoid this. These problems can be solved with further research. From the perspective of dwindling oil resources laser ignition system is good as it reduces the fuel consumption. From the environmental point of view, it is very significant since it considerably reduces the emission.

Seen as the current best alternative to conventional sparkplug

ignition system. Some of leading institutes and organizations researching and came with adaptive results are, University of Liverpool in collaboration with Ford Motor Company. National Energy Technological laboratory, United States of America. Colorado University& National Institutes of Natural Sciences-Japan.

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6.2 Practical Laser Sparkplug Requirements The simplest and least costly laser ignition design architecture would consist of a compact high peak power laser transmitter head, and a sapphire window/lens delivery system. The sapphire window is a well proven and reliable method of providing a transparent bulkhead seal on high pressure combustion chambers such as gas engine cylinder heads and the breeches of 155mm howitzers. BMLIS (Breech Mount Laser Ignition System) lasers, mounted directly on to the breech of large cannons, have over the last 20 years proven to be more reliable than fiber optic laser beam delivery systems. In these laser applications the laser window “self-cleaning” or “burning free” effect is well known. This is a laser ablation effect where ignition residue that collects on the window surface is blown free and clear of the optical aperture with each laser pulse. Many BMLIS, ARES and ARICE researchers are reaching the same conclusions about the attractiveness and dependability of direct fire laser ignition designs. Table 3: Potential Requirements of LIS

Mechanical Environmental

Laser and mounting must be hardened against shock and vibration Laser should perform over a large temperature range

Peak Power

Laser should provide megawatts raw beam output

Average Power

1-laser per cylinder requires 10Hz for 1200rpm engine operation

Lifetime

100 million shots – good, 500 million shots – better

Cost(ARES)

Laser cost less than $3,000 each (100M pulse life ~ break-even)

Cost (Auto)

Laser cost less than $600 each

The cost values shown for the natural gas engine laser spark plug are based upon the estimated operational costs of an 800 Kilowatt 16-cylinder Waukesha engine operating at 1200rpm with 16 lasers (one for each cylinder). At 1200 rpm the laser operates 24 hours a day, 365 days a year at 10 Hz (1200 rpm/2 strokes/ 60sec/min) for a total of approximately 315M pulses per year. We may also envision smaller and less costly laser spark plugs for use in common automobile 36

and truck engines. These applications may make use of very small low cost single emitter laser diodes to significantly reduce the laser spark plug component cost. Diode laser pumps are the costliest element employed in traditional side and end pumped DPSS Lasers. The diode lifetime is the limiting factor in the laser life time. The other criteria like below, Cost Concept proven but no commercial system yet available Stability of optical window Laser induced optical damage Particle deposit Intelligent control Laser distribution Multiple pulse ignitions Multiple point ignitions

6.3Application Laser ignition may be used in various applications besides high-speed, hypersonic aircraft. Examples include standard internal combustion engines, such as in automobiles and aircraft, as well as industrial combustion facilities which generate large amounts power. Laser ignition is considered as a potential ignition system for non-hypergolic liquid rocket engines and reaction control systems which need an ignition system. Conventional ignition technologies like torch igniters are more complex in sequencing and need additional components like propellant feed lines and valves. Therefore, they are heavy compared to a laser ignition system. Pyrotechnical devices allow only one ignition per unit and imply increased launch pad precautions as they are made of explosives. According to the latest international reports, Mazda’s upcoming rotary sports car could feature laser ignition technology. This would replace the spark plug ignition system which is currently applied to every petrol car on the market. It’s also a setup a revolution in spark plug which has been not change around 37

since 1860. Ford Motor Co. and researchers at the University of Liverpool are developing a car ignition system that swaps spark plugs for a laser beam to start vehicles while generating fewer greenhouse gas emissions.

Figure 26: Mazda RX-9 16X Rotar

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CHAPTER 7 CONCLUSION i.

The applicability of a laser-induced ignition system on direct injected gasoline engine has been proven by many experiments conducted around the world.

ii.

Application of this system would be a great step in reduction of environmental pollution.

iii.

As we are shifting towards hybrid system for better fuel economy then we can use this system also because the system is capable of burning leaner mixture that results in lower fuel consumption.

iv.

The optical window is capable of clean itself after several cycle so the maintenance would be very less and life is also very long that is 150 million shots (good) and 600 million shots (better).

v.

Ignition-delay times are smaller and pressure gradients are much steeper compared to conventional spark plug ignition.

vi.

At present, a laser ignition plug is very expensive compared to a standard electrical spark plug ignition system and it is nowhere near ready for deployment. But the potential and advantages certainly make the laser ignition more attractive in many practical applications.

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REFERENCES [1] Hrushikesh Mantri and Prof. Manoday Ramteke, “Laser Ignition System in IC Engine”, International Journal of Trend in Research and Development, ISSN: 2394-9333, Vol-3,2016. [2] Mr. Utsav Kothari, Mr. Pravin Bharane, Mr. Akashi Modasara, “Laser Ignition System for internal combustion engine”, International Journal of Engineering Sciences & Research Technology, ISSN: 2277-9655, Vol-5, 2016. [3] M. Srinivasnaik. T, Sudhakar, B. Balunaik, A. SomiReddy, “Laser Ignition System for Internal Combustion Engine”, International Journal of Engineering and Computer Science, ISSN:2319-7242, Vol-4, 2015. [4] Abhishek Saxena,”Laser ignition system in IC engines for cleaner environment”, International Advanced Research Journal in Science Engineering and Technology (IARJSET), ISSN: 2394-1588, Vol-2, 2015. [5] Swapnil Harel, Mohnish Khairnar, Vipul Sonawane,” Laser Ignition System for IC Engines”, International Journal of Science and Research (IJSR) ISSN: 23197064, Vol-1, 2015. [6] Vikas Sharma, “Laser Spark Ignition in lean burn CNG Engine”, IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE), ISSN: 2320-334X, Vol-11, 2014 [7] Mullett, J. D., Dodd, R., Triantos, G., Dearden, G., Shenton, A. T., Watkins, K. G., Carroll, S. D., Scarisbrick, A. D. and Keen.S, “Effects of laser parameters on laser ignition in an internal combustion engine”, Department of Engg. University of Liverpool, Vol-1,2006. [8] M. Lackner, F. Winter, “Laser Ignition in Internal Combustion Engines” A Contribution to a Sustainable Environment Institute of Chemical Engineering, Vienna University of Technology, Vol-1, 2006 [9] J. D. Dale by “Advancing lean combustion of hydrogen-air mixtures by laser induced ignition system” Brayford Pool, Lincoln, LN6 7TS, UK, Vol-3, 2007 [10] Ernst Wintner, Heinrich Kofler, Avinash Kumar Agarwal, “Annual Journal Of Electronics”, ISSN 1314-0078, Vol-2, 2014. 40

[11] Eiichi Takahashi, “A demonstration of laser ignition on natural gas engine”, Translation from Synthesiology, p.190-199, Vol-8, 2008. [12] Pankaj Hatwar, Durgesh Verma ”Laser Ignition in Internal Combustion Engines” International Journal of Modern Engineering Research ISSN: 341-345, Vol-2, 2012. [13] Bogdan Done, University POLITEHNICA of Bucharest, Faculty of Mechanical Engineering and Mechatronics, Department of Thermotechnics, Engines, Thermical and Frigorific Equipment, Splaiul Independentei no.313, Bucharest, Romania, Vol-1, 2011. [14] Michael J. Myers, John D. Myers, Baoping Guo, Chengxin Yang, Christopher R. Hardy,” Optical Technologies for Arming, Safing, Fuzing and Firing II”, SPIE Optics & Photonics San Diego, CA, Vol-1, 2007. [15] Michael Börner* and Chiara Manfletti** and Gerhard Kroupa, 7th European Conference For Aeronautics And Space Sciences (Eucass), Vol-2, 2007. [16] Http/physics-and-radio-electronics.com/physics/laser/ndyaglaser.html [17] Priyanka A. Kale, “Laser Assisted Ignition System for IC Engines”, International Journal of Pure and Applied Research in Engineering and Technology. IJPRET. ISSN: 2319-507X, Vol-3, 2015. [18] A.P. Yalin, M.W. Defoort, S. Joshi, D. Olsen, B. Willson, Y. Matsuura, M. Miyagi, " Laser Ignition of Natural Gas Using Fiber Delivery”, ASME Internal Combustion Engine Division 2005 Fall Technical Conference, ICEF2005-1336, pp.1-9, Vol-2, 2008.

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