Pistonless rotary engine

A pistonless rotary engine is an internal combustion engine that does not use reciprocating pistons in the way a reciprocating 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 more rotors, sometimes called rotary pistons, as described in QT-Wankel: Two Concepts 100 Years Apart. Although many different designs have been constructed, only the Wankel engine has achieved widespread adoption. The term rotary combustion engine has been used as a name for these engines to distinguish them from early (generally up to the early 1920s) aircraft engines and motorcycle engines also known as rotary engines which have radially disposed cylinders which rotate around a stationary crankshaft. However, both continue to be called rotary 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 the Rover JET1 but poor fuel efficiency, high noise levels, poor drivability and other issues prevented their use.