Centrifugal compressors work by increasing the velocity of gas molecules, converting their kinetic energy into pressure energy, thus increasing the pressure of compressed air. Reciprocating compressors (also called piston compressors) work by directly compressing gas, discharging it once a certain pressure is reached.
Commonly used air compressors on the market include piston air compressors, screw air compressors (screw air compressors are further divided into twin-screw and single-screw air compressors), centrifugal compressors, vane air compressors, and scroll air compressors. Below are the definitions of various compressor types. Cam-type, diaphragm-type, and diffusion pump compressors are not included because they have specific applications and are relatively small in size.
Positive displacement compressors – compressors that directly increase gas pressure by changing the gas volume. Reciprocating compressors – positive displacement compressors whose compression element is a piston that reciprocates within a cylinder. Rotary compressors – positive displacement compressors where compression is achieved by the forced movement of a rotating element. Sliding vane compressor – a rotary variable displacement compressor in which axial vanes slide radially on a rotor eccentric to the cylindrical body. Air trapped between the vanes is compressed and discharged.
Liquid-reciprocating compressor – a rotary positive displacement compressor in which water or other liquid acts as a piston to compress the gas and then discharge it.
Roots twin-rotor compressor – a rotary positive displacement compressor in which two Roots rotors mesh to trap the gas and direct it from the inlet to the outlet. There is no internal compression.
Screw compressor – a rotary positive displacement compressor in which two rotors with helical gears mesh to compress and discharge the gas.
Dynamic compressor – a rotary continuous flow compressor in which high-speed rotating blades accelerate the gas passing through them, converting velocity energy into pressure. This conversion occurs partly on the rotating blades and partly on the fixed diffuser or return baffle.
Centrifugal compressor – a dynamic compressor in which one or more rotating impellers (blades usually on the side) accelerate the gas. The main airflow is radial. Axial-flow compressors – a type of velocity compressor, in which gas is accelerated by a bladed rotor. The main airflow is axial. Mixed-flow compressors – also a type of velocity compressor, whose rotor shape combines some characteristics of both centrifugal and axial-flow compressors. Jet compressors – utilize high-speed gas or steam jets to carry away the intake gas, and then convert the velocity of the mixture into pressure in a diffuser.
