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SPARK PLUG WORKING AND TYPES

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Four stroke Petrol engine (spark ignition)

Introduction: The modern petrol engines operate on Otto cycle this cycle was introduced by German scientist Otto in 1876.


Although it was described by french scientist Beande Roches in 1862.


 Mainly Four strokes in the Petrol engines.


1. Suction stroke.


2. Compression stroke.


3. Power (working, expansion) stroke


4. Exhaust stroke.


     Suction stroke : 


   During this stroke the the piston moves downword by the crankshaft which is revolved by the momentum of the flywheel & the power generated by the electric motor the inlet valve remains open & exhaust valve is closed during stroke.


The downword movement of the piston sucks the air- fuel mixture in the cylinder from the carburettor through the open inlet valve. And the petrol mixed with air, this stroke complete here now the process move the next stroke.


     Compression stroke :


    During the compression stroke the piston moves upward direction and compressing the charge, the heat produced by the compression makes more homogeneous mixture of air and fuel inside the cylinder. The heat makes the petrol easier to burn while the compression forces it's closer to combination with the air 


The mixture in under compression is ignited by the spark produced by a spark plug & combustion is about half- completed when the piston is at TDC.


Both value remains closed during this stroke


TDC ; Top dead centre 


BDC ; Bottom dead centre.


    Power stroke :


In this stroke the expansion of the gasesdue to the heat of combustion exerts a pressure on the cylinder & piston. Under this impulse the moves downword direction thus doing useful work.


Both the valves remain closed during this stroke.


    Exhaust stroke : 


During this stroke the inlet valve is closed and exhaust valve open. The maximum part of the burnt gases escapes because of their own expansion. The piston moves upward and pushes the remaining gases out of the open exhaust valve.


Only a small amount of exhaust gases remains in the clearance space which will dilute the fresh incoming charge. 


In this type of engine, four stroke of the piston are required to complete the cycle and four stroke make two revolution of the crankshaft .The operation are repeated over & over again in running the engine. Each revolution of the crankshaft has one power stroke.





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