Flow Configuration (Centrifugal Compressor)
The casing, impeller, and flow arrangement chosen by the designer to attain compressor design requirements. Some of the most common flow designs are:
Straight Through: A common arrangement for a centrifugal compressor in which the casing consists of two nozzles, one is the suction or intake nozzle and the other the discharge nozzle. Gas enters the suction nozzle, passes through all the successive stages of compression, and leaves through the discharge nozzle into the piping system.
Back-To-Back: A compressor design in which impellers are not facing the same direction. This reduces the net thrust load developed by the rotor. A back-to-back arrangement is used in centrifugal compressors to minimize the need for a balance piston and to keep the thrust bearing size to a minimum.
Double Flow: A compressor arrangement where the gas flow is split into equal, smaller flows, which are fed into inlet connections at opposite ends of the casing. Both gas flows are compressed as they travel toward the center of the casing, where the flows combine and then exit the casing through a common discharge connection. Most double flow rotors are constructed so the rotor is located between two radial bearings.
Side Stream: Used in processes requiring several pressure levels from the compressor, such as refrigeration. This can be accomplished by using a side load. In this arrangement the main gas stream enters through an intermediate inlet nozzle. The two streams mix inside the casing and enter the next compression stage.