What is the primary engine component that converts thermal energy into mechanical energy?

The internal combustion engine is the primary component that converts thermal energy into mechanical energy. This process occurs within the engine's cylinders, where fuel is mixed with air and ignited to create a high-pressure environment. The combustion of fuel generates thermal energy, which causes the gases to expand rapidly. This expansion pushes the pistons within the cylinders, thereby transforming thermal energy into mechanical energy that powers the engine's output shaft.

While electric motors, steam turbines, and gas turbines also convert energy, they do so through different mechanisms. Electric motors convert electrical energy into mechanical energy, steam turbines use the thermal energy of steam generated from boiling water to turn blades, and gas turbines operate on a principle similar to internal combustion but use gas as the working fluid instead of liquid fuel. However, when focusing specifically on the conversion of thermal energy from fuel into mechanical power, the internal combustion engine stands out as the primary component used in many marine and land applications.