First, let’s cover some background on screw compressors.
As the screws continue to rotate, the gas becomes trapped between the compressor housings and rotors and is moved axially and radially through the rotor housing. The compression cycle begins when the gas filled thread is closed off from the suction port. Additional intermeshing of the lobes results in the reduction (compression) of the initial suction volume of gas until the gas is released through the outlet port. Compression discharge is determined by the location of the outlet port.