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. Due to recent progress in the area of high power fiber optics allowed convenient shielding and transmission of the laser light from one part of engine to the combustion chamber. Laser is emerging as a strong concept for alternative ignition in spark ignition engine. Laser ignition has potential advantages over conventional spark plug ignition. Laser ignition system is free from spark electrodes hence there is no loss of spark energy to the electrodes, which are also free from erosion effect. In addition 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, And many more. In this paper, advantages and disadvantages of laser and conventional spark ignition systems in the context of combustion engines are discussed, and performances of laser ignition and conventional spark ignition systems are comparatively evaluated in terms of Minimum Ignition Energy, Ignition Probability and Exhaust Emissions at similar operating conditions of the engine and graphs are plotted. And will also explain how laser ignition extends the lean flammability limit, while the spark ignition could be more favorable for rich mixture.

1. A SEMINAR ON :
A comparative study of laser
ignition and spark ignition with
gasoline–air mixtures.
Presented By :
Amiya Kumar Sahoo
Reg. no. : 11012227648
Group : 7ME-1A

2. INTRODUCTION
 An ignition system is a system for igniting a fuel-air mixture
 The process of combustion of fuel is initiated by the ignition
system
 In IC engines there are 2 types of ignition based on the fuel
 Spark Ignition (petrol engine)
 Compression Ignition (diesel engine)
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3. DRAWBACKS OF CONVENTIONAL
SPARK IGNITION
 Location of spark plug is not flexible as it require shielding of plug
from immense heat and fuel spray.
 It requires frequent maintenance to remove carbon deposits.
 Leaner air-fuel mixtures cannot be ignited.
 Degradation of electrodes at high pressure and temp.
 Multi point fuel ignition is not feasible.
 Flame propagation is slow.
 Higher turbulence levels are required.
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4. ADVANCE IGNITION METHODS
Some of the Advance ignition methods are :
 Ion sensing ignition
 Plasma jet ignition
 Rail-plugs ignition
 Laser induced spark ignition
 First demonstrated by J. D. Dale in 1978.
 Laser Ignition is the process of starting combustion by the
stimulus of a laser source.
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5. LASER
 The acronym LASER stands for Light Amplification by
Stimulated Emission of Radiations.
 It is Intense & Unidirectional beam of light.
 It is Monochromatic & Coherent.
 A Q-switched Nd:YAG laser of 532 or 1064nm
wavelength and with 6.6 or 7.9ns pulse width is used
for laser ignition.
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6. LASER GENERATION 6

7. WORKING OF Nd:YAG LASER 7

8. PRINCIPLE OF LASER IGNITION 8
1. Laser ignition begins with the initial seed electrons produced from
impurities in the gas mixture by focused laser beam.
2. Initial electrons readily absorb more photons and increase their kinetic
energy.
3. When the electrons gain sufficient energy ,they collide with other
molecules and ionize them, leading to an electron avalanche, And
optical breakdown the gas occurs .
4. This results in a well localized plasma with temperatures in the order of
106K and pressures in the order of 102 Mpa is formed.
This extreme condition leads to the development of a rapidly expanding
shock wave that is of sufficient strength to ignite flammable mixtures

9. ADVANTAGES OF LASER IGNITION
 Leaner mixtures can be ignited inside combustion
chamber.
 Lower combustion temperatures & less NOx emissions.
 High pressure and temperature does not affect the
performance allowing the use of high compression
ratios.
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10. ADVANTAGES OF LASER IGNITION
 Lifetime is high.
 Precise ignition timing possible.
 It does not require maintenance to remove carbon deposits because
of its Self cleaning property.
(1) (2)
1. After 20 h operation with spark plug ignition, heavily polluted
2. Immediately after 100 laser pulses. Beam area is cleaned by the laser beam.
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11. ADVANTAGES OF LASER IGNITION
 Shorter ignition delay time and shorter combustion time.
 Flame propagation is fast as multi-point fuel ignition is also
possible.
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Fig. Multi-point Ignition

12. 12
Parameters Laser Ignition Spark Ignition
Ignition Location Flexible Fixed
Multi-Point Ignition Possible Not feasible
Ignition of lean Mix. Can be ignited Cannot be ignited
Emission of NOx Very less More
Ignition Timing Precise(No misfire) Not Precise
Maintenance Low(Self-cleaning) Hgh
Lifetime High Low
COMPARISON BETWEEN LASER &
SPARK IGNITION

13. COMBUSTION CHAMBER
EXPERIMENT
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Fig. Experimental Setup
Components :
1.Nd:YAG Laser 5.Convex lens 9.Laser Energy Sensor
2.Beam attenuator 6.Mirror 10.Laser Energy Sensor
3.Beam Splitter 7.Convex lens( Focusing Lens) 11.Laser Energy Power
4.Concave lens 8.CVCC Meter

14. IGNTION PROBABILITY OF
LASER IGNITION
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 The probability of ignition is defined as the ratio of effective trails and
number of shots.
 The absorbed energy is exactly the energy necessary to yield ignition
inside the combustion chamber.

15. IGNTION PROBABILITY OF
LASER AND SPARK IGNITION
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 Spark ignition failed to ignite mixture of equivalence ratio 0.6
regardless of ignition energy
 In laser ignition maximum probability of ignition of equivalence ratio
0.6 was 65% for 532nm and 70% for 1064nm

16. MINIMUM ENERGY REQUIRED
FOR IGNITION
 The minimum ignition energy
required for laser ignition is more
than that for electric spark ignition
because of following reasons:
 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.
 Energy in the form of photons is
wasted before the beam reach the
focal point.
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17. NOx EMISSION POTENTIALS
250
190
70
330
240
0
50
100
150
200
250
300
350
17NOxin[mg/m³]
Direct Pre Chamber
Spark Ignition Laser Ignition
Direct Pre Chamber
Diesel Pilot Ignition

18. RESULT COMPARISON
80
90
100
110
Consumption Smoothness Emissions
(Percent)
Spark ignition between fuel
spray
Laser ignition between fuel
spray
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19. CONCLUSION
 The applicability of a laser-induced ignition system on engine
has been proven.
 Main advantages are the free choice of the ignition location
within the combustion chamber, even leaner mixtures can be
burned and Significant reductions in fuel consumption &
exhaust gases.
 At present, a laser ignition plug is very expensive as compared
to spark plugs.
 But potential advantages will surely bring it in to market for
many practical applications.
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20. THANK YOU