Air Engine

As in a steam engine, air engine expansion of externally supplied pressurized gas performs work against one or more pistons or rotors to move wheels or other tools. An air engine or air motor is a device for converting potential energy from compressed air into kinetic energy to drive other machines.

A compressed air vehicle can offer many of the advantages of a battery electric vehicle without the need for heavy and potentially toxic batteries, which take hours to recharge instead of the few minutes required to refill the tanks for an air engine. Like an electric vehicle, a compressed air vehicle will usually be pollution free during operation. However the energy required for compression must be sourced, and will usually be derived from electricity, or an internal combustion engine.

Depending on the method used to generate the electricity, the energy may contribute significant quantities of greenhouse gases and other pollutants, especially if fossil fuels or nuclear power are used. Although some air engines may be highly efficient, the system efficiency, including compression of the air, heat rejection, electricity losses and electricity generation, may be less than 25%.

The air engine and its idea of using air as an energy carrier is not new. Air has been used since the 19th century to power mine locomotives, and has been the basis of naval torpedo propulsion since 1866.

Compressed air is still currently used in racecars to provide the initial energy needed to start the car's main power plant, the internal combustion engine (ICE).

The most recent development uses pressurized air as fuel in an engine invented by Guy Nègre, a Formula One French engineer. In 1991, Guy Nègre started MDI, and invented a dual-energy engine, capable of running on both compressed air and regular fuel. From this moment on, he managed to create a compressed air only-engine, and improved his design to make it more powerful.

In the 15 years he's been working on this engine, considerable progress has been made: the engine is now claimed to be competitive with modern ICEs. It is probably still not as powerful as an ICE (although depending on which model of air engine vs model ICE). Proponents claim that this is of little importance since the car can simply be made lighter, or the tanks be put on a higher pressure, pushing the engine to above a comparable ICE-engine.

It uses the expansion of compressed air to drive the pistons of the engine, to propulse the vehicle or generate electricity. Efficiency of operation is gained through the use of environmental heat at normal temperature to warm the otherwise cold expanded air from the storage tank. This non-adiabatic expansion has the potential to greatly increase the efficiency of the machine.

The only exhaust gas is cold air (−15 °C), which may also be used for air conditioning in a car.

The source for air is a pressurized carbon-fiber tank holding air at around 20 MPa (3,000 psi, 200 bar). Air is delivered to the engine via a rather conventional injection system. Unique crank design within the engine increases the time during which the air charge is warmed from ambient sources and a two stage process allows improved heat transfer rates.

Armando Regusci's version of the air engine has several advantages over the original Nègre design. In the original Nègre air engine, one piston compresses air from the atmosphere, holding it on a small container that feeds the high pressure air tanks with a small amount of air. Then that portion of the air is sent to the second piston where it works. During compression for heating it up, there is a loss of energy due to the fact that it cannot receive energy from the atmosphere as the atmosphere is less warm than it.

Also, it has to expand as it has the crank. Nègre'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. In Regusci's version, the transmission system is direct to the wheel, and has variable torque from zero to the maximum, enhancing efficiency. When vehicle is stopped, Guy Nègre's engine has to be on and working, losing energy, while the Regusci's version need not.

In July 2004, Guy Nègre abandoned his original design, and showed later a new design that he stated to have invented in year 2001, but his new design is identical to the Armando Regusci's air engine which was patented back in 1989 (Uruguay) with the patent number 22976, and back in 1990 (Argentina). In those same patents, it is mentioned the use of electrical motors to compress air in the tanks.

Besides the compressed air engine designs by Regusci, Nègre, and EngineAir, the Quasiturbine is also capable of running on compressed air, and is thus also a compressed air engine.

Engines