Calculation of Rotor Interference in Screw Compressors

Small rotor clearances are today a vital prerequisite for an efficient screw compressor. The clearances are responsible for compressor leakages, small clearance will minimise them and thereby increase both, the volumetric and adiabatic efficiency. A continuous improvement in the rotor manufacturing equipment has been achieved during the recent years and tight production tolerances may now be applied to compressor rotors. This imposes a new approach upon the design of compressor elements, such as the rotor and bearing housings and bearings to respond properly to this challenge. A mathematical apparatus to quantify a change in rotor position in screw compressors due to the bearing clearance and the imperfections in compressor housing manufacturing is presented in this paper an applied for identification of their significance and influence upon the screw compressor behaviour. The analysis based on this approach has shown that the change in rotor position may have negative, either static or dynamic effects on the compressor efficiency, safety, endurance and reliability and enhancing compressor noise.