By PatriciaS

An air engine is another term for a pneumatic motor.  It uses compressed air to do the mechanical work of providing a continuous source of power.  This type of engine does not require electrical power and generate much less heat engines that do.  The three common types of air engines are vane, turbine and piston.

Vane Engines

Vane motors are also referred to as rotary engines.  They use axial vanes fitted into slots running throughout the length of the motor.   The vanes seal the interior chambers through springs, cam action or air pressure. The compressed air results in pressure in the chambers which allows the vanes to rotate, turning the motor so the air moves from one chamber to another.

Portable power tools are the main use for these types of air motors since they require low- to medium-power outputs. Increasing the number of vanes reduces the chances of internal leakage and blow-by. The result is that the motor torque output is more reliable at lower speeds,  and is uniform throughout the motor. Additional vanes can increase the friction and cost of the motor.

Turbine Motors

Turbine motors function by having a nozzle that guides the air into a turbine wheel.  This wheel is made from a rotor with curved blades and is set in motion when the air comes through the nuzzle and hits the blades.  Limiting the air flow through the motor will modify the amount of horsepower.  Dental drills are an example of a  general use for this low-pressure, high-velocity motor.

Their efficiency is higher than other air motors as the sliding contact of parts does not cause internal friction, thus there is no need for constant use of lubricating oil. The absence of lubrication improves the performance of the turbine motors in cold weather. They also require little maintenance, are compact and light for the power-delivery capability.

Piston Motors

High-power machines requiring a high-starting torque are the best use of piston motors.  This type of engine is composed of two to six cylinders housing pistons arranged in either a radial or axial fashion.  This design allows the air to move into the cylinders.  The cylinders rotate because the air pressure causes the pistons to slide outward. The torque turning the motor is the end result.

Since the power pulses overlap for motors with four or more cylinders, they have a smooth torque at a given operating speed.  Providing a better torque is detracted from by the increased chance that motors with two or more pistons will undergo a power stroke at any time during a revolution. Although piston motors have many advantages, they also have one significant limitation concerning their maintenance.  Oil supplies must be constantly checked and kept replenished.  This is due to their being internally oil lubricated.

Tags: air engine, turbine engine, vane engine, piston engine