Otto Cycle: Working of Otto Cycle

what is an Otto Cycle:


Otto Cycle: In this article we will learn about Otto cycle and working of Otto cycle. Otto cycle is an internal combustion system which explains using thermodynamic cycle, Otto cycle has relatively same function to the petrol engine, which contains spark plug.

Otto cycle process includes four steps:

  • Isentropic expansion.- Air and fuel is compressed.
  • Heat addition at constant volume.- Combustion takes place.
  • Isentropic expansion.- Gases in cylinder gets expanded to high temperature and pressure.
  • Heat rejection at constant volume.-Emits the gases out from cylinder.

Otto Cycle is introduced by Nikolaus Otto, in 1891.

This type of engine there is a spark plug to ignite the Air-Fuel mixture in the cylinder but in diesel engines(CI) they do not use any separate igniting device. The thermal efficiency of Otto cycle = Heat supplied – Heat rejected/Heat supplied. Otto cycle is an reversible process but in actual application it is an irreversible. Otto cycle has less efficiency than diesel.

Working of Otto Cycle:


At first, the air from the atmosphere is drawn into the cylinder in suction stroke by moving the piston towards down, after that, air and fuel gets compressed,  the mixture of air-fuel gets heated to high temperature and at this time spark plug used to ignite the compressed Air-fuel. after this, the energy produced by it pushes the piston towards downward and used for external work.Otto cycle generates the power is given by energy developed per unit of time.

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