Combustion is the primary source of noise in most naturally aspirated direct injection diesel engines. In turbocharged diesel engines, combustion noise is less dominant at high-speed and high load steady-state conditions but can become dominant at idle, light-load or under acceleration .
An external combustion engine (EC engine) is a heat engine where a working fluid, contained internally, is heated by combustion in an external source, through the engine wall or a heat exchanger. The fluid then, by expanding and acting on the mechanism of the engine, produces motion and usable work.
The combustion produces a high temperature, high pressure gas stream that enters and expands through the turbine section. The turbine is an intricate array of alternate stationary and rotating aerofoil-section blades. As hot combustion gas expands through the turbine, it spins the rotating blades.
The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. All parts rotate consistently in one direction, as opposed to the common reciprocating piston engine, which has pistons violently changing direction.