Carnot engines are the most effective because they are reversible and all reversible engines will have the same efficiency.
Leonard Carnot proposed the Carnot engine, a hypothetical thermodynamic cycle.
An ideal closed thermodynamic cycle with reversibility is known as a Carnot cycle.
In this cycle, isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression are the four sequential processes that take place.