User:Crosbiesmith/Otto cycle

The Otto cycle is a thermodynamic cycle which describes the processes at work within a reciprocating, spark-ignition, internal combustion engine. It is named for German inventor Nicolaus Otto who began manufacturing such engines in 1868. It is the cycle used in all gasoline-fueled car engines.

Idealised Otto cyle
An Otto cyle engine is a type of heat engine, in which four thermodynamic processes are carried out in sucession: Compression, Heat addition, Expasion, and Heat Rejection.

In an Otto cycle engine, each of these takes place within a cylinder. The working fluid is typically air. A piston is used to alternately compress and expand the air within the cylinder. Compressed air is heated in the cylinder.

The four steps of the Otto cyle therefore are:
 * 1) the piston uses mechanical energy to compress the gas within the cylinder.  Compression is adiabatic, meaning no heat is transferred.
 * 2) Heating of the air within the cylinder at constant volume
 * 3) adibiatic expansion of the gas within the cylinder against the piston produces mechanical power
 * 4) Heat rejection - the expanded gas is allowed to cool to ambient temperatures

Because the mechanical energy released in 4. is greater than the mechanical energy used in 2. to compress the gas, a net release of mechanical energy occurs.