Analysis of Internal Clearance of Oil-Free Screw Compressor and Its Application to Performance Simulation

Clearance between male and female rotors and that between the rotors and casing of an oil-free screw compressor in operation are calculated. Surface displacement vectors of both rotors due to, for example, thermal deformation, profile errors, and deviation of the center distance, are converted to such that the clearance between the rotors changes assuming that the rotor surface is approximated by a plane in the vicinity of the calculating point and that the normal line of the plane does not change direction before or after the displacements. The calculation is applied to a computer simulation for predicting air compressor performance. Change in volumetric efficiency related to suction air temperature was calculated and the results agreed well with experimental ones.