What is mean by ignition limit? Give ignition limit for SI engine.
Ignition Limit corresponds approximately to that mixture ratio, at lean & rich ends of the scale, where the heat released by spark is no longer sufficient to initiate combustion in the neighboring un-burnt mixture. The flame will propagate only if the temperature of the burnt gases exceeds approximately 1500 K in the case of hydrocarbon-air mixture. The lower & upper ignition limits of the mixture depend upon mixture ratio & flame temperature. The ignition limits are wider at increased temperature because of higher rates of reaction.
Theoretical Ignition limits for Hydrocarbon fuels are 7:1 to 30:1
Actual Ignition limits for hydrocarbon fuels are 9:1 to 21:1