Traditionally, most compressors are reciprocating compressors; fluid is compressed through piston mechanism, positive displacement. Reciprocating compressors can be used in a wide range of applications from household to gas and oil refineries. Today, centrifugal compressors are common and are used to increase pressure of a certain fluid/gas and reduce fluid volume. They are suited for high volume applications due to its nature of continuous flow and few moving parts. They are widely used in automotive applications such as turbocharges, chemical plants, gas turbines, etc.
A centrifugal compressor is a dynamic compressor, which depends on the work done by a rotating impeller on the fluid. The fluid enters form the center of the system and is directed outwards, away from the centre. The momentum of the fluid is converted to useful pressure by slowing the fluid down in a stationary diffuser.
A centrifugal compressor can be designed as a multi-stage system to achieve higher pressure and efficiency. The diffuser of the centrifugal compressor is connected again to the shaft of another centrifugal compressor. The compressed fluid is therefore compressed further.
Most centrifugal compressors operate at high RPM. Tight tolerances and balancing requirements of the rotor have been a challenge. Balancing is often difficult to perform because the shape of impeller can be very complex. Depending on the fluid, impeller may be be corroded during operation. This requires shut-down and re-balancing. The table shows common fault types found in centrifugal compressors.