Compressed-air engine

A Compressed-air engine is a Pneumatic actuator that creates useful work by expanding compressed air. They have existed in many forms over the past two centuries, ranging in size from hand held turbines up to several hundred horsepower. Some types rely on pistons and cylinders, others use turbines. Many compressed air engines improve their performance by heating the incoming air, or the engine itself. Some took this a stage further and burned fuel in the cylinder or turbine, forming a type of internal combustion engine.

Tools

Impact wrenches, drills, die grinders, dental drills and other pneumatic tools use a variety of air engines or motors. These include vane type pumps, turbines and pistons.

Torpedoes

Most successful early forms of self propelled torpedoes used high pressure compressed air, although this was superseded by internal or external combustion engines, steam engines, or electric motors.

Railways

Compressed air engines were used in trams and shunters, and eventually found a successful niche in mining locomotives, although eventually they were replaced by electric trains, underground. Over the years designs increased in complexity, resulting in a triple expansion engine with air to air reheaters between each stage.

Aircraft

Transport category airplanes, such as commercial airliners, use compressed air starters to start the main engines. The air is supplied by the load compressor of the aircraft's auxiliary power unit, or by ground equipment.

Automotive

There is currently some interest in developing air cars. Several engines have been proposed for these, although none have demonstrated the performance and long life needed for personal transport.

Energine

The Energine Corporation is a South Korean company that delivers fully-assembled cars running on a hybrid compressed air and electric engine. The compressed-air engine is used to activate an alternator, which extends the autonomous operating capacity of the car.

EngineAir

EngineAir, an Australian company, is making a rotary engine powered by compressed air, called The Di Pietro motor. The Di Pietro motor concept is based on a rotary piston. Different from existing rotary engines, the Di Pietro motor uses a simple cylindrical rotary piston (shaft driver) which rolls, with little friction, inside the cylindrical stator.

It can be used in boat, cars, carriers and other vehicles. Only 1 psi (≈ 6,8 kPa) of pressure is needed to overcome the friction.

K'Airmobiles

K'Airmobiles vehicles use a compressed-air engine known as the K'Air, developed in France by a small group of researchers

These engines have a consumption of compressed air of less than 120 L/min., although developing a dynamic push able to reach 4kN.

The technical concept of the K'Air pneumatic engines returns to direct conversion of what makes the fundamental characteristic of compressed air, namely:

* the pushing force of compressed air is exclusively exploited for conversion into kinetic energy of translation,
* itself is simultaneously converted into induced power of rotation of the axis and
* thus gives to the engine a particularly imposing torque while needing only a very low “fuel” consumption.

To simplify, one can compare the principle to that of the rotary jacks:

* the energy of the fluid (compressed air) is directly transformed into rotational movement;
* the double-acting jacks involve a pinion-toothed rack system;
* the cyclic angle of rotation can vary between 90 and 360°;
* it supports hydraulic supercharging systems.

MDI

In the original Nègre air engine, one piston compresses air from the atmosphere to mix with the stored compressed air (which will cool drastically as it expands). This mixture drives the second piston, providing the actual engine power. MDI's engine works with constant torque, and the only way to change the torque to the wheels is to use a pulley transmission of constant variation, losing some efficiency. When vehicle is stopped, MDI's engine had to be on and working, losing energy. In 2001-2004 MDI switched to a design similar to that described in Regusci's patents (see below), which date back to 1990.

Quasiturbine

The Pneumatic Quasiturbine engine is a compressed air pistonless rotary engine using a rhomboidal-shaped rotor whose sides are hinged at the vertices.

The Quasiturbine has demonstrated as a pneumatic engine using stored compressed air .

It can also take advantage of the energy amplification possible from using available external heat, such as solar energy.

The Quasiturbine rotates from pressure as low as 0.1 atm.

Since the Quasiturbine is a pure expansion engine (which the Wankel is not, nor are most other rotary engines), it is well suitable as compressed fluid engine - Air engine or air motor.

Regusci

Armando Regusci's version of the air engine couples the transmission system directly to the wheel, and has variable torque from zero to the maximum, enhancing efficiency. Regusci's patents date back to 1990,

Team Psycho-Active

Psycho-Active is developing a multi-fuel/air-hybrid chassis which is intended to serve as the foundation for a line of automobiles. Claimed performance is 50 hp/litre

Karts

At least one Kart has been powered by a quasiturbine.

Efficient air engines

One could make the compressed air engines much more efficient than they are now (15%) by for example:

* Using the heat energy from the compressor (ALL energy used to run the compressor is converted to heat due to friction),
* shut down the air after a while ("cutoff"),
* Expand the air in several various stages and heat the air again between the expansions by ordinary air (in a heat exchanger),