Pneumatic motor

A pneumatic motor (Air motor) or compressed air engine is a type of motor which does mechanical work by expanding compressed air. Pneumatic motors generally convert the compressed air energy to mechanical work through either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor, piston air motor, air turbine or gear type motor.

Pneumatic motors have existed in many forms over the past two centuries, ranging in size from hand-held motors to engines of up to several hundred horsepower. Some types rely on pistons and cylinders; others on slotted rotors with vanes (vane motors) and other uses turbines. Many compressed air engines improve their performance by heating the incoming air or the engine itself. Pneumatic motors have found widespread success in the hand-held tool industry, but are also used stationary in a wide range of industrial applications. Continual attempts are being made to expand their use to the transportation industry. However, pneumatic motors must overcome inefficiencies before being seen as a viable option in the transportation industry.

Hot air engine

A hot air engine (historically called an air engine or caloric engine) is any heat engine that uses the expansion and contraction of air under the influence of a temperature change to convert thermal energy into mechanical work. These engines may be based on a number of thermodynamic cycles encompassing both open cycle devices such as those of Sir George Cayley and John Ericsson and the closed cycle engine of Robert Stirling. Hot air engines are distinct from the better known internal combustion based engine and steam engine.

In a typical implementation, air is repeatedly heated and cooled in a cylinder and the resulting expansion and contraction is used to move a piston and produce useful mechanical work.

Definition

The term "hot air engine" specifically excludes any engine performing a thermodynamic cycle such as the Rankine cycle, in which the working fluid undergoes a phase transition. Also excluded are conventional internal combustion engines in which heat is added to the working fluid by combustion of fuel within the working cylinder. Continuous combustion types such as George Brayton's Ready Motor and the related gas turbine could be seen as borderline cases.