A robust calculation method of meshing clearance for screw rotor pairs

Abstract

This study proposes a novel calculation method for meshing clearance between two mating screw rotors in compressors and vacuum pumps. The meshing clearance is obtained by calculating the minimum distance between the helix curves and the rotor surface. The 3D contact points of the screw rotor pair are found by applying the proposed algorithm. In particular, this method is robust enough to precisely calculate the clearance for the rotor type with several singular points where the shortest distance direction misaligns with the normal direction of the rotor surface. As demonstrated in the numerical examples, the proposed method is possible to estimate the clearance between two mating screw rotors with constant or variable pitch, as well as feasible to analyze the meshing clearance between two unconjugated rotors. In addition, differences in the clearance distribution of a variable-pitch screw pair with yaw and pitch misalignments are predictable. These results validate the robustness and flexibility of the proposed method.