An analysis of manufacturing factors’ influences on the actual screw compressor rotors’ profile clearances

One of the most important parameters, which have high influence on screw compressor characteristics, are rotors' profile clearances. They determine in general the smooth of the rotors' gearing and influence on the screw compressor vibration level. Analyse of actual rotor profile clearances depending on the actual rotor temperature fields and on the manufacturing imperfection was done. Specially profiled milling tools were chosen as rotor profile manufacturing tools. Following four types of the manufacturing error, which have the highest influence on the accuracy and quality of rotors' profile surface, were chosen to analyses: the centre distance deviation between the rotor and the milling tool axises (dAi), the departure of the milling tool position from their basic plate (dZf), the milling tool mounting position angle departure (dβ) and the milling tool radii departure (dRf).The actual screw compressor profile coordinates can be obtained by taken into account all factors presented above. They determine the actual rotor profile clearances on "cold" state when screw compressor is on shutdown conditions and can be measured during a compressor assembling or a compressor stripping. However, it should be noted that they are changed depending on the screw compressor working conditions. To correctly determining actual profile clearances depending on working condition also needs to take into account rotors' thermal deformation. The presented multifaceted approach of the screw compressor actual rotor profile clearances calculation improves an accuracy compressor characteristic obtained by their mathematical model. A deep analysis of the obtained results can pointed to the rotors' manufacturing factors, which should be improved firstly during the compressors' mass production.