Post on 19-Jul-2016
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04/28/2023 1
“Laser Ignition of IC Engine”
Submitted To,SARDAR VALLABHBHAI NATIONAL INSTIYUTE OF TECHNOLOGY, SURAT(INDIA)
Prepared By,Beladiya Bharatkumar BP12TD020
Guided by,Mr. V. P. RathodAsst. Professor,M.E.D, SVNIT, Surat
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“Laser Ignition of IC Engine”Introduction
Ignition system of any SI engine is responsible to initiate thecombustion of air-fuel mixture inside the combustion chamber
For ensuring good performance and efficiency of the engine as well as lower emissions, spark is triggered at precisely right instant in every cycle
Over the years, spark ignition systems have changed significantly The conventional ignition system contains a battery, a switch, anignition coil, a distributor, a triggering device (contact breaker), anda spark plug
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“Laser Ignition of IC Engine”Ignition System
Ignition systems can be classified based on the methods of
Ignition energy storage Distributing the voltageTriggering the ignition timing
The development of electronic controls to trigger ignition and use ofdistributor-less ignition system has made the ignition system moreeffective and reliable
However ignition systems pose a limitation in the development of future,efficient SI engines.
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“Laser Ignition of IC Engine” Limitations of Spark Ignition System
Spark Plug Erosion High Pressure OperationSpark LocationHeat Losses at the Spark Electrodes
Spark plug erosion is caused by the interaction of electrical dischargeplasma with the electrode surface
There are various mechanisms by which electrode’s material can erode Particle injection, Vaporization of electrode material, and Sputtering
The reasons for spark plug erosion can be summarized as : Removal of material is due to disintegration of the surface material Spark discharge Chemical attacks such as oxidation or corrosion
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“Laser Ignition of IC Engine”Alternative Ignition System
Alternative ignition systems have potential to improve the delivery of ignition energy
However higher spark energies are also associated with the erosion of sparkElectrodes
Electrodes act as a thermal energy sink
A durable, high-energy, electrode-less ignition system with controlled energy deposition in the plasma, having flexibility to change the ignition location is a desirable option for overcoming these limitations in lean mixture fuelled reciprocating IC engines
Laser ignition system, which meets most of these requirements, offerspotential advantages for igniting lean mixtures.
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“Laser Ignition of IC Engine”How does a Laser work?Lasers are monochromatic, meaning they are very orderly forms of light that have only one wavelength and one direction.
It all starts with the electrons. By sending energy to a system we can achieve what is known as population inversion. This means that there are more electrons in the excited states than those in the lower energy states. As one electron releases energy (a photon), the other electrons strangely seem to communicate with each other and also begin releasing photons. This chain reaction of releasing photons is called stimulated emission. The problem now is that these photons are released in random directions. In order to make sure this energy is all forced in the same direction, mirrors are strategically laced within a laser to direct the photons. The photons are directed by bouncing back and forth between the mirrors, hitting each other and causing more stimulated emission.
So, by having:- Population Inversion- Stimulated Emission- Strategic Planting of Mirrors
We get:- Monochromatic , Directional, and Coherent light.
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“Laser Ignition of IC Engine”Types of LasersGas-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 weaponrySemiconductor-Also known as laser diodes, a semiconductor laser is one where the active medium is a semiconductor similar to that found in a light-emitting diode.
Applications include telecommunication and medicine
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“Laser Ignition of IC Engine”Principle of Laser Ignition focused laser beam
plasmaI>Ithreshold
flame kernelE>Eignition
mixture burning
Convex Lens
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“Laser Ignition of IC Engine”
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“Laser Ignition of IC Engine”How Laser Ignition Works
The laser ignition system has a laser transmitter with a fiber-optic cable powered by the car’s battery. It shoots the laser beam to a focusing lens that would consume a much smaller space than current spark plugs. The lenses focus the beams into an intense pinpoint of light, and when the fuel is injected into the engine, the laser is fired and produces enough energy (heat) to ignite the fuel. Below is a diagram of the laser arrangement:
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“Laser Ignition of IC Engine”
Increase of spark plug voltage versus rising break
mean effective pressure BMEP
Increase of spark plug voltage versus rising break mean effective pressure BMEP
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“Laser Ignition of IC Engine”
330
240
70
250
190
0
50
100
150
200
250
300
350NOX [mg/Nm³]
directdirectdirect Pre Chamber Pre ChamberLaserSpark Ignition Diesel Pilot Ignition
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“Laser Ignition of IC Engine”
6 ns
7 ns
8 ns
9 ns
10 ns
11 ns
12 ns
13 ns
14 ns
15 ns
16 ns
18 ns
20 ns
22 ns
25 ns
30 ns
35 ns
40 ns
45 ns
50 ns
60 ns
70 ns
80 ns
Various stages of plasma growth
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“Laser Ignition of IC Engine”
2 4 6 80
2
4
6
8
MP
E (m
J)
A/Frel
( )
pinit
= 5 bar p
init = 10 bar
pinit
= 20 bar
Laser energy, required to ignite mixture, decreases with increasing pressure of chamber
Minimum Laser Pulse Energy
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“Laser Ignition of IC Engine”
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
0 100 200 300 400 500 600 700 800 900 1000
Time (ms)
Exce
ss P
ress
ure
(MPa
)
λ = 2.5, laser
λ = 3.0, laser
λ = 3.5, spark plug
λ = 3.5, laserλ = 3.0, spark plug
λ = 2.5, spark plug
Pressure History in Combustion Chamber
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“Laser Ignition of IC Engine”
ignition reliability of laser ignition
A/F rel ( )1,40 1,50 1,60 1,70 1,80 1,90 2,00 2,10 2,20 2,30
pin
it (b
ar)
10
15
20
25
30
35
40
0,00 0,25 0,50 0,75 1,00
ignition reliability of spark plug ignition
A/F rel ( )1,40 1,50 1,60 1,70 1,80 1,90 2,00 2,10 2,20 2,30
pin
it (b
ar)
10
15
20
25
30
35
40
0,00 0,25 0,50 0,75 1,00
For 100% ignition reliability at 30 barA/Frel = 2.05 (laser ignition)A/Frel = 1.74 (spark ignition)
Direct comparison laser ignition – spark plug ignition
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“Laser Ignition of IC Engine”Graphical comparison of laser and spark ignition with respect to fuel consumption, smoothness of running and emissions from test results
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“Laser Ignition of IC Engine”Knock and misfire limits
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“Laser Ignition of IC Engine”Flame propagation in combustion chamber
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“Laser Ignition of IC Engine”Multiple Ignition Approach
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“Laser Ignition of IC Engine”Advantages of Laser Ignition
A choice of arbitrary positioning of the ignition plasma in thecombustion cylinder.• Absence of quenching effects by the spark plug electrodes.• Ignition of leaner mixtures than with the spark plug• lower combustion temperatures => 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 => increase in 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.• Fuel-lean ignition possible.
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“Laser Ignition of IC Engine”
Challenges
Propagation of laser pulse through fiber optics
Develope of a compact, robust and economic laser source
Durability of windows
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Plasma propagates towards the incoming laser beam
Plasma had the maximum emission peak 30 ns after the laser was fired and laser plasma UV-emission persisted for about 80 ns
Minimum laser pulse energy (MPE) for ignition is decreases with increasing initial pressure
The time of pressure rise in case of laser ignition is shorter than the spark ignition
Conclusions
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