Otto Cycle

An Otto cycle, named after Nicolaus Otto, is an idealized thermodynamic cycle describing the functioning of a typical spark-ignition piston engine, the cycle most commonly found in automobile engines. It describes what happens to a gas as it is subjected to changes of pressure, temperature and volume together with the addition and removal of heat, treating the fluid inside the cylinder as the system under study. The cycle is built from two isentropic, frictionless and adiabatic processes at the top and bottom of its loop and two constant-volume, or isochoric, processes on its two sides; because the isentropic compression and expansion involve no heat transfer into or out of the system, work is performed on the system during the lower compression process while heat flows in through one pressurizing process and partly back out through a depressurizing process, and the balance of work and heat added minus heat removed yields the net mechanical work the system generates.