FOUR STROKE ENGINE , WORKING OF PETROL ENGINE

 FOUR STROKE ENGINE

WHAT IS ENGINE ?

       In the simple language engine is a power plant of vehicle which provides power  to all the unit parts of the vehicle those needs power. it is usually mounted at the front end of the car. 



 classification of engine

  •   According to strokes 
  1. four stroke engine
  2. two stroke engine
  • According to combustion 
  1. internal combustion
  2. external combustion
  • According to ignition
  1. spark ignition 
  2. compression ignition
WORKING OF ENGINE ( PETROL)
four stroke engine consist four cycles (stroke)
  1. Suction stroke ( intake)
  2. compression stroke
  3. expansion or power stroke 
  4. exhaust stroke
  • SUCTION STROKE
Suction stroke starts whens piston is at the top dead centre and moves downwards. during suction stroke inlet valves is open . due to piston moving downwards low pressure region is created inside the cylinder and fresh air fuel mixture inters in cylinder at the same time the exhaust valve will closed. at the end of the suction stroke inlet valve closes


  • COMPRESSION STROKE
During the compression stroke piston moves from bottom dead centre to top dead centre and due to this compression of air fuel mixture charge takes place. During this stroke both the inlet valve and outlet valve are closed, and charge which occupied whole cylinder volume compressed upto only clearance volume
just before the completion of the compression stroke spark produced by spark plug and fuel get ignite
thus combustion of fuel takes place due to the spark hence engine called as ' spark ignition engine '


  • EXPANSION OR POWER STROKE
Piston gets downwards due to explosion of charge . due to high pressure of burnt gases, piston moves
from top dead centre to bottom dead centre
during the expansion stroke both the inlet and outlet valve are closed. poer is obtained by expansion of products of  combustion. therefor it is also called as ' power stroke '


  • EXHAUST STROKE
AT the end of expansion stroke the exhaust valve open , the inlet valve remain closed and piston moves from bottom dead centre to top dead centre 
During exhaust stroke the burnt gases are throw out side the cylinder the exhaust valve closes at the and of the exhaust stroke

Each cycle of four stroke engine completes the above four stroke or operation in two crank revolutions
one revolution of crank shaft occurs during the suction and compression and second revolution during the power and exhaust stroke

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