Discuss in brief process of combustion in SI engines with a sketch.

Discuss in brief process of combustion in SI engines with a sketch.
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1 Answer

Answer :

Combustion In S I Engine

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According to Ricardo, There are three stages of combustion in SI Engine as shown in figure above 1. Ignition lag stage 2. Flame propagation stage 3. After burning stage


1. Ignition lag stage:

There is a certain time interval between instant of spark and instant where there is a noticeable rise in pressure due to combustion. This time lag is called IGNITION LAG.


2. Flame propagation stage:

Once the flame is formed at “b”, it should be self sustained and must be able to propagate through the mixture. This is possible when the rate of heat generation by burning is greater than heat lost by flame to surrounding. After the point “b”, the flame propagation is abnormally low at the beginning as heat lost is more than heat generated.


3.After burning:

Combustion will not stop at point “c” but continue after attaining peak pressure and this combustion is known as after burning. This generally happens when the rich mixture is supplied to engine. 

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