A turbine converts hydraulic energy into mechanical energy. A compressor converts mechanical energy into heat or pressure energy. A turbine is a prime mover. A compressor has to be driven by a prime mover.

The diffuser is an important element of a compressor or pump. Its purpose is to reduce the velocity of the flow leaving the impeller resulting in an increase in pressure. The diffuser can be simply depicted as a nonrotating channel whose flow area increases in the direction of flow (Figure 7.7).

A centrifugal compressor imparts kinetic energy into the airstream by increasing the velocity of the air using a rotating element and then converts this kinetic energy into potential energy in the form of pressure.

The first type of compressor is the centrifugal or annular compressor. The other type of compressor is the axial flow compressor. While axial compressors can accomodate more airflow than a centrifugal design of the same size, a rotor/stator stage generally does not provide enough compression for most applications.

Generally centrifugal compressors are limited to two stages due to efficiency concerns. The two main functional elements are the impeller and the diffuser.

There are two basic types of compressors – axial flow and centrifugal flow.

Approximately 55 to 65 percent of the power produced by the turbine is used to drive the compressor. To optimize the transfer of kinetic energy from the combustion gases to shaft rotation, gas turbines can have multiple compressor and turbine stages.

centrifugal compressors

While turbines can be classed as either impulse or reaction according to the way they function, there are four broad types of turbines categorized according to the fluid that supplies the driving force: steam, gas, water, or wind.