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Otto four stroke cycle engines – petrol engines

  • Description about operation of otto four stroke cycle engine in diagram and important points in simple way.
  • Air and fuel mixed in proper ratio and enter in to the engine cylinder
  • Spark plug is used to produce spark, which is used to burn the air-fuel mixture
  • Therefore this engine is called spark ignition engine
  • In this cycle operation is completed by four strokes as described bellow

otto-four-stroke-cylcle-engines-petrol-engines

Suction Stroke

  • In this stroke piston move from top dead centre (T.D.C) to bottom dead centre (B.D.C)
  • Intake valve is opened and the proportion of air-fuel mixture enter into the engine cylinder
  • This operation indicated by the line (E-A) in p-v diagram

Compression stroke

  • In this stroke piston move form bottom dead centre (B.D.C) to top dead centre (T.D.C)
  • This operation represented by the line (A-B) in p-v diagram
  • In this operation air-fuel is compressed and pressure is increased nearly 8 bar
  • At the end of this stroke spark is released by spark plug in the air-fuel mixture
  • Then air-fuel mixture is burn in the cylinder and at this time period inlet and exhaust valves are closed





Expansion stroke

  • Due to burning of air-fuel mixture hot gases will produced with high pressure
  • Then piston move from T.D.C to B.D.C and therefore work is produced in this stroke
  • Fly wheel is used to store the energy produced in this stroke and use this energy for reaming three stroke
  • This operation indicated by the line (C-D) in p-v diagram
  • In the starting of this stroke inlet and exhaust valves are closed
  • At the end of this stroke inlet valve is closed and exhaust valve is opened





Exhaust stroke

  • This is last stroke of this cycle, gases produced in the expansion stroke are send out to the atmosphere in the exhaust stroke
  • The piston moves from B.D.C to T.D.C and gases remove from the engine cylinder to out is called scavenging
  • This operation indicated by the line (A-E)

otto-four-stroke-cylcle-engine-theoretical-p-v-diagram

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