An air compressor is a machine used to convert power from a diesel engine, gasoline engine or electric motor into kinetic energy. This is done by compressing and pressurizing the air which is in turn released in quick bursts. There are various types of air compression and they can be divided into either negative or positive displacement types. There are four basic types of air compressors and they are; reciprocating compressors, centrifugal compressors, rotary screw compressors and the axial flow compressors. The difference is that they each use different air compressor filters. They can also be further classified by the cooling methods, drive method and number of compression stages.

Reciprocating air compressors

A reciprocating air compressor is an example of a positive displacement machine. They work by reducing volume to increase the air pressure. This also means that a lot of air is being taken in and confined to a closed space and hence the air is elevated to even higher pressure. The reciprocating air pressure functions by using a piston within a cylinder as the displacement and compressing element.

Rotary screw compressors

This is also a positive displacement compressor. The most common of the rotary screw compressors is the spiral lobe oil flooded or the single stage helical screw air compressor. The types of compressors come with two rotors within a casing where the air is compressed internally. They have no valves and are usually oil cooled and the internal clearances are sealed by oil. Since the cooling takes place inside the compressor, the other working parts are rarely affected by the extreme temperatures while the machine is working. The rotary compressor can therefore be said to be a whole package of a continuous duty, air and water cooled compressor. The rotary compressor also uses a special type of filter for it to work effectively. The effectiveness in the operation of these machines will also be dependent on the precisely fitting clearances that are between the rotors and the sealing chamber for the compression cavities.
These compressors tend to be smooth running and compact but with limited vibration and thus do not require spring suspension.

Centrifugal compressors

This is a dynamic kind of a compressor that depends on the transfer of energy from a rotating impeller into the air. Centrifugal compressors produce discharge that is high pressured by converting the angular momentum that is imparted by the rotating impeller/dynamic displacement. In order for this to work effectively, the centrifugal compressors have to rotate at a higher speed that that of other compressors. These kinds of compressors are also designed for higher capacity functions since the flow through the compressor is continuous.

Axial flow compressors

These are air foiled base, rotating compressors which work by flowing fluids parallel to the axis or rotation. This is in contrast with the other compressors like centrifugal, mixed flow and axial- centrifugal compressors where the air enters through the axial but has a significant radial component at the exit.