Pre-ignition
Pre-ignition is the ignition of the homogeneous mixture of charge as it comes in contact with hot surfaces, in the absence of spark. Auto ignition may overheat the spark plug and exhaust valve and it remains so hot that its temperature is sufficient to ignite the charge in next cycle during the compression stroke before spark occurs and this causes the pre-ignition of the charge. Pre-ignition is initiated by some overheated projecting part such as the sparking plug electrodes, exhaust valve head, metal corners in the combustion chamber, carbon deposits or protruding cylinder head gasket rim etc. pre-ignition is also caused by persistent detonating pressure shockwaves scoring away the stagnant gases which normally protect the combustion chamber walls. The resulting increased heat flow through the walls, raises the surface temperature of any protruding poorly cooled part of the chamber, and this therefore provides a focal point for pre-ignition.
Effects of Pre-ignition
-It increase the tendency of denotation in the engine
-It increases heat transfer to cylinder walls because high temperature gas remains in contact with for a longer time
-Pre-ignition in a single cylinder will reduce the speed and power output
-Pre-ignition may cause seizer in the multi-cylinder engines, only if only cylinders have pre-ignition
Pre-ignition is the ignition of the homogeneous mixture of charge as it comes in contact with hot surfaces, in the absence of spark. Auto ignition may overheat the spark plug and exhaust valve and it remains so hot that its temperature is sufficient to ignite the charge in next cycle during the compression stroke before spark occurs and this causes the pre-ignition of the charge. Pre-ignition is initiated by some overheated projecting part such as the sparking plug electrodes, exhaust valve head, metal corners in the combustion chamber, carbon deposits or protruding cylinder head gasket rim etc. pre-ignition is also caused by persistent detonating pressure shockwaves scoring away the stagnant gases which normally protect the combustion chamber walls. The resulting increased heat flow through the walls, raises the surface temperature of any protruding poorly cooled part of the chamber, and this therefore provides a focal point for pre-ignition.
Effects of Pre-ignition
-It increase the tendency of denotation in the engine
-It increases heat transfer to cylinder walls because high temperature gas remains in contact with for a longer time
-Pre-ignition in a single cylinder will reduce the speed and power output
-Pre-ignition may cause seizer in the multi-cylinder engines, only if only cylinders have pre-ignition
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