Laser ignition system (3) (1)

LASER IGNITION SYSTEM 2014
1
A
BOOK REPORT
ON
LASER IGNITION SYSTEM
BY T.E.MECHANICAL –B3 BATCH
PRANITA POL 37
RAHUL PADWAL 39
SHREEDHARSANGOALKAR 42
ROHAN SAWANT 45
SUJIT SHETTY 51
RADHA SINGH 54
UNDER THE GUIDANCEOF
Assistant prof. Miss. RIDDHI POPAT

2
DATTA MEGHE COLLEGE OF ENGINEERING
A BOOK REPORT ON
SUBMITTED TO
Assistant prof. Miss. RIDDHI POPAT
SUBMITTED BY
TE MECHANICAL-B3 BATCH
PRANITA POL 37
RAHUL PADWAL 39
ROHAN SAWANT 45
SUJIT SHETTY 51
RADHA SINGH 54
INTHE PARTIAL FULLFILLMENTOF REQUIREMENT
OF MUMBAI UNIVERSITY

3
LASER IGNITION SYSYTEM

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We the students of Vth
semester of MECHANICAL
ENGINEERING, have successfully completed the book report as a part
of our curriculum as stated by MUMBAI UNIVERSITY. We have
successfully completed the book report as described in this report by
own skills and study as per instructions and guidance of Miss. Riddhi
Popat.
We clarify that we have not copied the report or its any appreciable
part from any Literature in contravention of any academic ethics.
Team Members-
PRANITA POL 37
RAHUL PADWAL 39
ROHAN SAWANT 45
SUJIT SHETTY 51
RADHA SINGH 54

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TABLE OF CONTENTS
Abstract
Acknowledgement
List of figures
Introduction
Aimand scope
1.1 Introductionof system
1.2 Laser
1.2.1 Types of laser
1.3 Plasma
2.1 Laser ignitionsystem
2.2 Combustions
2.3 Laser igniters
2.4 present scenario
3.1 Comparison betweenspark and laser ignition
3.1.1 spark ignitionsystem
3.1.2 Laser ignitionsystem
3.2 Advantages
4.1 Discussion
4.2 Conclusion
5.0 References

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ABSTRACT
Laser ignition with its many potential advantages in comparison to
conventional spark plug ignition has been investigated in detail. As
ignition source several, to a certain extent exclusive prototype ns, Q-
switched Nd:YAG lasers were used. Experiments were performed in a
constant volume, high pressure/temperature combustion chamber
and with two gasoline research engines. On one engine a mechanical
& thermal robust, passive Q-switched, diode pumped Nd:YAG laser
combined with special optimized optics was mounted directly on the
research engine. Despite the harsh environment on the engine, the
laser ignition system was able to operate the engine more than 10
hours. It turned out that the laser can ignite far leaner mixtures than
with the conventional spark plug which means a significant reduction
of NOx. Further on, the ignition delay and combustion time is shorter
and the coefficient of variation (COV) of the induced mean effective
pressure (IMEP) is significantly smaller. The use of this system should
be initiated on heavy trucks and not on cars considering the high cost
of the system.

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ACKNOWLEDGEMENT
It is indeed a matter of great pleasure and proud privilege to be
able to present this Book report on "LASER IGNITION SYSTEM".
The experience gained in the execution of a given book report is
worth a milestone in a student’s life and the efforts taken to bring out the
best in our capacity speaks volumes about the co-ordinated efforts. We
are highly indebted the report guide Ms. RIDDHI POPAT for her
invaluable guidance and appreciation for giving form and substance to
this report. It is due to her enduring efforts; patience and enthusiasm,
which has given a sense of direction and purposefulness to this book
report and ultimately made it a success.
We would like to tender our sincere thanks to the staff members
for their co-operation.
We would wish to thank the non - teaching staff and our friends
who have helped us all the time in one way or the other. Really it is
highly impossibleto repay the debt of all the people who have directly or
indirectly helped us for preparing the book report.

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LIST OF FIGURES
1.Laser ignition engine
2.Ruby laser
3.Plasma formation by a focused beam
4.Principle of laser ignition
5.Optical breakdown in air generated by Nd-Yag laser
6.Combustion chamber
7.Spray guided combustion using laser beam
8.Single and multipoint ignition
9.Setup of laser system for the first engine tests
10.Spark plug ignition in an internal combustion engine.
11.Laser ignition system for an internal combustion engine.

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INTRODUCTION
With the increasing disadvantage of spark plug ignition
system, it is becoming essential to find an alternative to the
spark plug ignition system.spark plug ignition system is unable
to burn the fuel mixture completely inside the combustion
chamber,whereas the alternative to it-the laser ignition
system burns air fuel mixture completely and runs the engine
for a longer time compared to spark plug ignition system. This
project presents the overall scenario of the working of laser
ignition system which as the name suggests makes use of the
laser.

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AIM AND SCOPE
Our report on “Laser ignition system” seeks to share useful
innovations both in thoughts and in practice with the aim of
encouraging information exchange and the subsequent benefits
that are borne of scrutiny, experimentation and debate . It is
our hope that the work shared in this project will inform
practices that strengthen the knowledge of the mentioned
subject and encourage the access for the topic.

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1.1) INTRODUCTION
For more than 150 years, 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 mini explosion 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. In laser ignition system
laser igniters on the other hand, could ignite leaner mixtures without self
destructing 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.
Figure 1.Laser Ignition Engine

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1.2)LASER
Lasers provide intense and unidirectional beam of light. Laser light is
monochromatic (one specific wavelength). Wavelength of light is determined
by amount of energy released when electron drops to lower orbit. Light is
coherent; all the photons have same wave fronts that launch to unison. Laser
light has tight beam and is strong and concentrated. To make these three
properties occurtakes something called “Stimulated Emission”, in which
photon emission is organized. Main parts of laser are power supply, lasing
medium and a pair of precisely aligned mirrors. One has totally reflective
surface and other is partially reflective (96 %). The most important part of
laser apparatus is laser crystal. Most commonly used laser crystalis manmade
ruby consisting of aluminum oxide and 0.05% chromium. Crystal rods are
round and end surfaces are made reflective.
A laser rod for 3 J is 6 mm in diameter and70 mm in length
approximately. Laser rod is excited by xenon filled lamp, which surrounds it.
Both are enclosed in highly reflective cylinder, which directs light from flash
lamp in to the rod. Chromium atoms are excited to higher energy levels. The
excitations meet photons when they return to normal state. Thus very high
energy is obtained in short pulses. Ruby rod becomes less efficient at higher
temperatures, so it is continuously cooled with water, air or liquid nitrogen. The
Ruby rod is the lasing medium and flashtube pumps it.
Figure 2. Ruby Laser

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1.2.1)TYPES OF LASER
• Gas
– A Helium-Neon (HeNe) used mostly for holograms such as laser
printing.
• Chemical
– Lasers that obtain their energy through chemical reactions. Used
mostly for weaponry.
• Dye
– Uses organic dye as the lasting medium, usually in the form of a
liquid solution. Used in medicine, astronomy, manufacturing, and
more.
• Solid-state
– Uses a gain medium that is a solid (rather than a liquid medium as
in dye or gas lasers). Used for weaponry
1.3)PLASMA
The most dominant plasma producing process is the electron cascade
process: Initial electrons absorb photons out of the laser beam via the inverse
bremsstrahlung process. If the electrons gain sufficient energy, they can ionise
other gas molecules on impact, leading to an electron cascade and breakdown of
the gas in the focal region. 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 avalanche process. In contrast to
multiphoton ionisation (MPI), no wavelength dependence is expected for this
initiation path

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Figure 3.Plasma Formation by a Focused Beam
2.1)LASER IGNITION SYSTEM
Laser ignition or laser-induced ignition, is the process of starting
combustion by the stimulus of a laser light source. 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. Multiphoton absorption processes are usually essential for the initial
stage of break down 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 multiphoton 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 depend upon the absorption
properties of the laser and the minimum energy required depends upon the
number of photons required for producing the electron avalanche.
The minimum ignition energy required for laser ignition is more than
that for electric spark ignition because of following reasons: An initial

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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 10^-3 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 reaches the focal point. Hence
heating and ionizing the charge present in the path of laser beam. 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.
Figure 4. Principle of laser ignition

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Basically, energetic interactions of a laser with a gas may be classified into one
of the following four schemes as listed below:
1) Thermal initiation
 Ignition occurs without the generation of an electrical breakdown.
 A laser beam is used to raise the kinetic energy of target molecules.
 Molecular bonds are broken and chemical reaction occurs leading to
ignition .
 Long ignition delay times.
 Best suited for solid fuels.
2) Non-resonantbreakdown
 Laser light is tightly focused so that the intensity exceeds the
breakdown threshold of the gas.
 Once breakdown is achieved, a plasma spark is formed which absorbs
the laser energy.
 Energy is transferred to the combustion gases from the spark and
starts the reaction
 Commonly used technique because of the freedom in selection of
laser wavelength and implementation.
3) Resonantbreakdown
 Similar to non-resonant breakdown in that the end results is a plasma
spark.
 The wavelength of the laser must be tuned to the particular resonance.
 This lowers the number of photons required for photo ionization, and
hence the amount of energy required to cause breakdown.
4) Photochemicalmechanisms

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 This method starts ignition by creating radicals, and in general does
not heat the gas as do the previous three methods.
 If the productionrate of the radicals is higher than the neutralizing
radicals then the highly active species will reach a threshold value,
leading to an ignition event
Figure 5. Optical breakdown in air generated by a Nd:YAG laser
2.2)COMBUSTIONS
After a successful ignition event the flame propagates through the
combustible. Usually, one can distinguish between different types of
combustion processes.
1. Slow combustion processes (deflagrations): Reaction velocity is mainly
determined by heat conductivity. Propagation velocity is less than the
speed of sound.

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2. Fast combustion processes (detonations): Reaction velocity is
determined by a strong shock front moving at supersonic velocity.
Propagation velocity is greater than the speed of sound.
Figure 6. Combustion chamber
Figure 7. Spray Guided Combustion using Laser Beam

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2.3)LASER IGNITERS
A new laser system invented by researchers could displace the
venerable design of spark plugs, which has stood virtually unchanged for the
past 150 years. Lasers, by contrast, could focus their beams into the middle of
the column, from which point the explosion would expand more symmetrically
– and reportedly up to three times faster than one triggered by a spark plug.
Additionally, engine timing could be improved, as lasers can pulse within
nanoseconds, while spark plugs require milliseconds. 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 milli-joules 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, and then embedding them with metal ions in order to tune
their properties. Made from two bonded yttrium-aluminum-gallium segments,
the laser igniter is just 9 millimeters wide and 11 millimeters long. It has two
beams, which can produce a faster, more uniform explosion than one by igniting
the air-fuel column in two locations at once –the team is even looking at
producing a laser with three beams. While it cannot cause combustion with just
one pulse, it can do so using several 800-picosecond-long pulses.
Figure 8.Single & Multi-point Ignition

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2.4)PRESENTSCENERIO
Lasers promise less pollution and greater fuel efficiency, but making
small, powerful lasers has, until now, proven hard. To ignite combustion, a laser
must focus light to approximately 100 giga-watts per square centimeter with
short pulses of more than 10 millijoules each. 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 powders 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.
The composite generates two laser beams that can ignite fuel in two
separate locations at the same time. This would produce a flame wall that grows
faster and more uniformly than one lit by a single laser. The laser is not strong
enough to light the leanest fuel mixtures with a single pulse. By using several
800- picoseconds-long pulses, however, they can inject enough energy to ignite
the mixture completely. A commercial automotive engine will require 60 Hz (or
pulse trains per second), Researchers have already tested the new dual-beam
laser at 100 Hz. Researchers are also at work on a three-beam laser that will
enable even faster and more uniform combustion. The laser-ignition system,
although highly promising, is not yet being installed into actual automobiles
made in a factory. Scientist team from Japan is, however, working with a large
spark-plug company and with DENSO Corporation, a member of the Toyota
Group.

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Figure 9. Set-up of the laser systemfor the first engine tests
3.1)COMPARISON BETWEENSPARK& LASER IGNITION
3.1.1 Spark ignition System
Conventional spark plug ignition has been used for many years and is a well
established and reliable technology. The fuel-air mixture is compressed and at
the right moment a high voltage is applied to the electrodes of the spark plug.
For ignition of an inflammable gas mixture, the energy balance has to be
positive within a small volume. The supplied energy together with the
exothermal heat of the reaction have to be greater than the necessary activation
energy and losses due to heat conduction or radiation. This technology has been
used very successfully a million times in combustion engines from the very
beginning till now. Nevertheless, problems occur due to the fact that the ignition
location cannot be chosen optimally. Additionally, spark plug electrodes can
disturb the gas flow within the combustion chamber.

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Figure 10.Spark Plug Ignition in an Internal Combustion Engine
 LIMITATIONS OF SPARK PLUG
Spark plugs only ignite the area of the air-fuel mixture closest to them
(the top), with much of the heat of the explosion being absorbed by the metal
cylinder walls before it can reach down to the piston. The fuel inside the
combustion chamber is not burnt completely by the conventional spark plug.
Spark plug burn the air-fuel mixture which is slightly on richer side than air-fuel
mixture, we can use in laser igniters. Spark plugs can ignite leaner fuel
mixtures, but only by increasing spark energy. Unfortunately, these high
voltages erode spark plug electrodes so fast, the solution is not economical.
3.1.2 Laserignition system
Laser ignition uses an optical breakdown of gas molecules 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 a
hot and bright plasma is generated, see fig. 11.

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Figure 11.Laser Ignition System for an Internal Combustion Engine
3.2)ADVANTAGES
The main advantages of laser ignitions are given below:
1) A choice of arbitrary positioning of the ignition plasma in the
combustion cylinder
2) Absence of quenching effects by the spark plug electrodes
3) Ignition of leaner mixtures than with the spark plug; lower combustion
temperatures and less Nox emissions
4) 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
5) High load/ignition pressures possible, increase in efficiency Precise
ignition timing possible
6) Exact regulation of the ignition energy deposited in the ignition plasma
7) Easier possibility of multipoint ignition
8) Shorter ignition delay time and shorter combustion time

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4.1)DISCUSSION
4.2)CONCLUSION
In this paper, it is 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 efficiency.
5) REFERENCES
 H. Kopecek, S. Charareh, M. Lackner, C. Forsich, F. Winter, J. Kausner,
G. Herdin, E. Wintner, "Laser Ignition of Methane-Air Mixtures at High
Pressure and Diagnostics", Journalof Enginesand GasTurbine
Power, 127 pp. 213-219
 J.D. Dale, P.R. Smy, R.M. Clements, "Laser Ignited Internal Combustion
Engine - An Experimental Study", Society of Automotive Engineers,
780329, pp. 1539-1548
 T.X. Phuoc, "Laser Spark Ignition: Experimental Determination of Laser-
Induced Breakdown Thresholds of Combustion Gases", Optical
Communications, 175 pp. 419-423
 D. Bradley, C.G.W. Sheppard, I.M. Suardjaja, R. Woolley,
"Fundamentals of High-Energy Spark Ignition with Lasers", Combustion

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and Flame,138pp. 55-77
 A.P. Yalin, M.W. Defoort, S. Joshi, D. Olsen, B. Willson, Y. Matsuura,
M. Miyagi, " Laser Ignition of Natural Gas Using Fiber
Delivery",Proceedings of ICEF 2005, ASME InternalCombustion Engine
Division 2005 FallTechnicalConference, ICEF-2005-1336, pp. 1-9
 A.P. Yalin, A.R. Reynolds, S. Joshi, M.W. Defoort, B. Willson, Y.
Matsuura, M. Miyagi, " Development of a Fiber Delivered Laser Ignition
System for Natural Gas Engines", Proceedings of ICEF, ASME Internal
Combustion Engine Division 2006 Spring Technical Conference, ICEF-
2006-1370, pp. 1-6

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