What are the processes in an ideal Otto combustion cycle?

In an ideal Otto combustion cycle, the processes consist of two constant volume processes and two isentropic processes.

To understand why this is the case, let's break down the cycle into its four distinct processes. The Otto cycle typically involves:

1. Isentropic compression: The air-fuel mixture is compressed adiabatically (without heat transfer) from a lower volume to a higher volume, which increases the temperature and pressure of the mixture. This process is isentropic, meaning it ideally occurs without any entropy change.

2. Constant volume heat addition: Once the compression is complete, the heat is added to the compressed mixture at constant volume. This heat addition occurs when the fuel is ignited, causing a rapid rise in pressure and temperature while the volume remains constant.

3. Isentropic expansion: After combustion, the high-pressure gases expand adiabatically, doing work on the piston. During this process, the temperature and pressure decrease, but, like the first process in the cycle, there is no heat transfer, and it is also isentropic.

4. Constant volume heat rejection: Finally, the cycle ends with a heat rejection process at constant volume, where the remaining exhaust gases release heat