What is used in petrol engine to ignite the fuel?

What is used in petrol engine to ignite the fuel?


a. fuel injector
b. fuel igniter
c. combustion chamber
d. spark

Correct Answer: d. spark


In four-stroke petrol engine, one thermodynamic cycle is completed by the four complete strokes by the piston. A single travel of the piston in cylinder in either direction is nothing but a one stroke of the piston.

four stroke petrol engine

The four strokes are given below:

In the intake stroke the piston moves from top dead centre of the cylinder by allowing the air-fuel mixture inside the cylinder through inlet port. The exhaust port is closed in this stroke.

In the compression stroke both the inlet and exhaust port are closed and the piston moves from bottom dead centre to top dead centre of the cylinder with compressing the air-fuel mixture in the cylinder head.

In the power stroke the compressed air-fuel mixture in spark ignition engine is ignited by providing spark through spark plug. Due to instant ignition of the compressed fuel high pressure is produced and this pressure forces the piston to downside at high thrust. Therefore this is a power stroke.

In the exhaust stroke the piston again returns to the top dead centre while exhaust valve is open and this stroke allows the spent fuel-air mixture through the exhaust port.
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