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“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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“Laser Ignition of IC Engine”

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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“Laser Ignition of IC Engine”

THANK YOU