The Cyclic Process of Birth to Extinction of

The Cyclic Process of Birth to Extinction of Flame in SI Engines P M V Subbarao Professor Mechanical Engineering Department Spark is External Driven Event…. Flame is a Signature left by the Spark….

Reaction Vs Action

Energy Available for Gas : Growth of Spark • At breakdown, the spark length is equal to the spark gap and then, the spark is stretched by convection and by the turbulent motion of the flow. •

Volume of the Sparking Gas Considering the spark as a cylindrical channel of length lspark, the channel radius is: In the spark discharge studies it is found that inside spark Tspark = 35, 000 K for a gas with 300 K & and 0. 1 MPa. Every fuel injection system must ensure these conditions are sustained after breakdown of spark for successful ignition.

Effect of velocity on energy to be supplied by Secondary Coil Remark: when the mixture is moving ignition is more difficult Energy Supplied by Coil, ES, m. J Geometrical Model for Kernel due to spark ignition in flow.

Energy Supplied by Coil, ES, m. J Control of Turbulence Level for Efficient Ignition

The effect of the spark plug gap on the brake specific fuel consumption

The effect of spark energy on BSFC

Other Ignition systems 1. 2. 3. 4. 5. 6. 7. Ignition By An Electrically Heated Wire Ignition By Flame or Hot Jet Plasma Jet Ignition Photochemical Ignition Microwave Ignition Laser Ignition Puff-jet Ignition

Laser Ignition • The importance of the spark time scale on the flame kernel size is well recognized. • A laser ignition source has the potential of improving engine combustion with respect to conventional spark plugs. • A laser based ignition source, i. e. replacing the spark plug by the focused beam of a pulsed laser. • Laser ignition, or laser-induced ignition, is the process of starting combustion by the stimulus of a laser light source. • It was tried to control autoignition by a laser light source. • The time scale of a laser-induced spark is by several orders of magnitude smaller than the time scales of turbulence and chemical kinetics. https: //www. osapublishing. org/oe/fulltext. cfm? ur i=oe-27 -8 -A 385&id=407533

The Concept of Laser Ignition

Arrangement and Control of Ingition Region

Phases in Laser Ignition • The different phases of laser ignition can be defined in chronological order • Electric breakdown and energy transfer from laser to plasma • Shock-wave generation and propagation • Gasdynamic effects • Chemical induction of branching chain reactions of radicals leading to ignition • Turbulent flame initiation

Time Scales in Laser Ignition

Selection of Wave Length

Effectiveness of Laser Ignition

Control of Ignition Region

Impact of Laser Ignition : 1

Impact of Laser Ignition : 2

Thermodynamic Model for Ignition of Compressed Air Mixture in SI Engine Air+Fuel vapour + fuel droplets +Residual gas Compression Process Result of successful Ignition:

Conditions for Survival of Baby Flame • It is considered that a flame kernel can be formed around the spark due to a successful ignition. • Micro volume of burnt gas mass is deposited at the spark, which corresponds to a cylinder of radius 2 L and length lspk. The burnt mass generated by a successful spark is: What is the shape of the burnt gas volume left by the spark after withdrawal of spark? How does this grow after ? ? ?

Test Rig for Listening to the Cylinder

Phenomenological Understanding of Ignition to Combustion Initiation of Ignition Crank Angle,

Add Wisdom to The Listening

Pressure & dp/d Vs Crank Angle

Rate of Combustion (Heat Release rate)

Phenomenological Understanding: Ignition to Combustion End of Combustion Start of Combustion Initiation of Ignition Crank Angle,