The Otto cycle is a thermodynamic cycle that models the operation of spark-ignition internal combustion engines, such as those found in most gasoline-powered vehicles.
Key characteristics:
- It consists of four distinct processes: two isentropic (adiabatic and reversible) and two isochoric (constant volume).
- The cycle includes:
- Adiabatic compression of the air-fuel mixture.
- Constant-volume heat addition (spark ignition and combustion).
- Adiabatic expansion (power stroke).
- Constant-volume heat rejection (exhaust).
Why it’s important:
- The Otto cycle explains how chemical energy from fuel is converted into mechanical work.
- Its efficiency depends on the compression ratio of the engine—the higher the ratio, the more efficient the cycle, in theory.
While real engines have losses due to friction, heat dissipation, and incomplete combustion, the Otto cycle provides a simplified, ideal model that helps engineers design and analyze engine performance.