Research Of The Backflow Characteristic And Optimization Design Of Screw Vacuum Pump

The relationship between the geometric parameters of the screw rotor and the backflow characteristic as well as dynamic balance characteristic in the single thread and fixed pitch screw vacuum pump was studied and analyzed, and important components such as the screw rotor, inlet and exhaust port were optimized, a reference for the structure design of the screw vacuum pump was provided.1) The influence of rotor geometrical parameters on the area utilization coefficient was analyzed by the meshing principle and the geometric pumping speed was calculated, the equation of contact line was studied, the graph of contact line was drawn and the length of the contact line was obtained by solving the meshing condition equation, providing basis for studying the backflow;2) Based on fluid mechanics, the theoretical mathematical model of the backflow through gaps was established, the influence of different clearance and rotor parameters to the backflow was analyzed, and the rule between the backflow and rotor parameters such as outer screw radius, inner screw radius, base circle radius and screw pitch was obtained, the optimization design of screw rotor was presented.3) The critical speed of the screw rotor was obtained through modal analysis, the influence of rotor geometric parameters on the original unbalance was studied, and the shape and parameters of balance hole were obtained to balance the rotor;4) The internal and external compression process in screw vacuum pump was analyzed, the effect of different volume ratio on power consumption and temperature of exhaust gases were studied, and then the cross section shape of inlet and outlet port was optimally designed combined with the change rule of the tooth volume.