A pistonless rotary engine is an

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal comb ...

that does not use

piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder (engine), cylinder a ...

s in the way a

reciprocating engine A reciprocating engine, more often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common features of al ...

does. Designs vary widely but typically involve one or more

rotor ROTOR was an elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bombers. To get it operational as quickly as possible, it was initially made up primarily of WWII-era syst ...

s, 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 The Wankel engine (, ) is a type of internal combustion engine using an eccentric (mechanism), eccentric Pistonless rotary engine, rotary design to convert pressure into rotating motion. The concept was proven by German engineer Felix Wankel, f ...

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 engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbin ...

s and

motorcycle engine A motorcycle engine is an engine that powers a motorcycle. Motorcycle engines are typically two-stroke or four-stroke internal combustion engines, but other engine types, such as Wankel engine, Wankels and electric motors, have been used. Altho ...

s also known as ''

rotary engine The rotary engine is an early type of internal combustion engine, usually designed with an odd number of cylinders per row in a radial configuration. The engine's crankshaft remained stationary in operation, while the entire crankcase and its ...

s''. However, both continue to be called ''rotary engines'' and only the context determines which type is meant, whereas the "pistonless" prefix is less ambiguous.

Pistonless rotary engines

A pistonless rotary engine replaces the linear reciprocating motion of a piston with more complex compression/expansion motions with the objective of improving some aspect of the engine's operation, such as: higher efficiency

thermodynamic cycles A thermodynamic cycle consists of linked sequences of thermodynamic processes that involve transfer of heat and work into and out of the system, while varying pressure, temperature, and other state variables within the system, and that eventuall ...

, lower mechanical stress, lower vibration, higher compression, or less mechanical complexity. 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 *

LiquidPiston The red line is a three lobe epitrochoid, which is the shape of the LiquidPiston's swept volume The X-engine is a type of pistonless rotary engine manufactured by LiquidPiston of Bloomfield, Connecticut. The X engine is a hybrid cycle rotar ...

engine * Beauchamp Tower's nineteenth centur
spherical steam engine
(in actual use as a steam engine, but theoretically adaptable to use internal combustion) Development stage * Engineair engine * Hamilton Walker engines *Libralato rotary

Atkinson cycle The Atkinson-cycle engine is a type of internal combustion engine invented by James Atkinson (inventor), James Atkinson in 1882. The Atkinson cycle is designed to provide Energy conversion efficiency, efficiency at the expense of power density. ...

engine * Nutating disc engine * RKM engine, *

Sarich orbital engine The Sarich orbital engine is a type of internal combustion engine, invented in 1972 by Ralph Sarich, an engineer from Perth, Australia, which features orbital rather than reciprocating motion of its central piston. It differs from the conceptual ...

Swing-piston engine A swing-piston engine is a type of internal combustion engine in which the pistons move in a circular motion inside a ring-shaped "cylinder", moving closer and further from each other to provide compression and expansion. Generally two sets of pist ...

, Trochilic * Wave disk engine Conceptual stage *

Gerotor A gerotor is a positive displacement pump. The name ''gerotor'' is derived from "generated rotor (turbine), rotor." A gerotor unit consists of an inner and an outer rotor. The inner rotor has ''n'' teeth, while the outer rotor has ''n'' + 1 ...

engine *Internally Radiating Impulse Structure: IRIS engine

Pistonless rotary engines

See also

References

Further reading