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Four stroke petrol Engines

         

                 









So in our previous blogs we have discussed about the basic meaning and function of an IC Engine. Please visit the previous blog for a better learning experience .Now let us take a look at the technical working of a 4 Stroke Petrol Engine or Spark ignition engine(SI engine) ....

Before getting into the main topic let us understand the meaning of the word "Stroke" and why is it called by that name.Basically if a process has to happen it has to undergo a set of steps or stages of  the  process a IC engine the stages are known as "stroke".
Now let us see how a 4 stroke IC engine works....
  • Suction Stoke.
  • Compression Stroke.
  • Power Stroke.
  • Exhaust Stroke.




1. Suction Stroke:During this stroke,the inlet valve(the valve through which air-fuel mixture enters). and the exhaust valve is closed and the piston is top dead Centre (TDC).

2.Compression Stroke:During compression stroke,both inlet and exhaust valve remains closed and piston is Bottom dead centre (BDC). During this stroke,the piston moves upward and the due to this action, there is buildup of pressure and temperature. Just before the end of this stroke,the spark plug ignites the mixture.One revolution of the crank is compled at this stage.The fuel is burnt.

3.Power Stroke: Same like previous stroke, the inlet and exhaust valves are closed in this phase due to pressure build up of pressure and temperature,force is exerted by the burnt gases on the piston and due to this process the pressure and temperature decreases till it reaches BDC. This is known as power stroke or working stroke.At this position, the exhaust valve is opened. 


4.Exhaust Stroke:After the valve is opened the pressure falls and the piston moves from BDC to TDC by pushing all the combusted product out by Exhaust Valve. The cycle repeats after it reaches TDC by opening the inlet valve and closing the exhaust valve.

    




 

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