| The rotors of screw vacuum pump were taken as the main research object in this paper. The screw rotor profile of screw vacuum pump and the rotor’s thermal load was studied. Meanwhile, structural of screw vacuum pump was optimized. The main contents of this dissertation are shown as follows:1) Basis on the conjugate meshing principle of curve, curves were studied which are epicycloid type profile, inner cycloid type profile, exterior cycloid type profile, involute type profile. The influence of profile lines on the coefficient of useful area, the meshing line and the leakage triangle were analyzed. The characteristics of profile lines are summarized. The result can provide theoretical basis for profile line’s design.2) The thermodynamic process of screw vacuum pump and the temperature field boundary conditions of rotors and casing were calculated. The rotors and casing were established in finite element method. Thermal load of system was calculated. The influence of the geometries of the pump parts, on the temperature distributions and variations in gap widths because of thermal deformation was investigated. The change of gap in working process of system was analyzed. The result can provide the foundation for optimization design of assembly clearance of screw vacuum pump.3) Analysis models of different cooling structures were established. The influence of the geometries of the pump parts, on different cooling structures because of thermal deformation was investigated. The gaps of different cooling structures was calculated, and theory calculation formula was concluded. The outcome definite the relationship between assembly clearance and pumping speed.4) Considering the meshing characteristics and thermal deformation of rotors, rotor structure were optimized. A rotor structure were proposed. Using rotors shape compensate thermal deformation of rotor’s discharge end, which make backflow decreased so as to improve the pumping performance of screw vacuum pump. |
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