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Apistonless rotary engine is aninternal combustion engine that does not use reciprocatingpistons in the way areciprocating engine does, but it still relies on the same distinct induction, compression, ignition, exhaust phases and the same enclosed volumes and gas pressure increase due to combustion to generate power. Designs vary widely but typically involve one or morerotors, sometimes calledrotary pistons, as described in QT-Wankel: Two Concepts 100 Years Apart.[citation needed] Although many different designs have been constructed, only theWankel engine has achieved widespread adoption.
The termrotary combustion engine has been used as a name for these engines[citation needed] to distinguish them from early (generally up to the early 1920s)aircraft engines andmotorcycle engines also known asrotary engines which have radially disposed cylinders which rotate around a stationary crankshaft. However, both continue to be calledrotary engines and only the context determines which type is meant, whereas the "pistonless" prefix is less ambiguous.gas-turbine engines can also be described as rotary combustion engines. their practical applications include helicopter rotor drive. During the 1950s gas turbines were considered to be a viable option for road cars and a number of prototypes were built by various manufacturers, one of the first being theRover JET1 but poor fuel efficiency, high noise levels, poor drivability and other issues prevented their use.
A pistonless rotary engine replaces the linear reciprocating motion of a piston with a generally rotary and sometimes more complex compression/expansion mechanism with the objective of improving some aspect of the engine's operation, such as: higher efficiencythermodynamic cycles, reduced physical size and weight, lowermechanical stress, lower vibration, highercompression, or less mechanical complexity. As of 2006[update] the Wankel engine is the only successful pistonless rotary engine, but many similar concepts have been proposed and are under various stages of development. Examples of rotary engines include:
Production stage
Development stage
Conceptual stage
