Theory And Performance Study Of A New Segmented Elliptical Roots Vacuum Pump Rotor

In order to solve the problem that the traditional circular arc Roots rotor has small average flow rate,large flow pulsation and pressure pulsation at outlet,a novel elliptical rotor composed of elliptical arc and elliptical arc conjugate envelope is proposed in this paper.The analytical equations and the range of angle parameters of each profile are obtained by using meshing principle and kinematics solving method.Based on the differential geometry,the undercutting and carryover of the novel elliptical rotor are analyzed,and the condition of undercutting and carryover of the novel elliptical rotor is obtained.The rotor program without undercutting and carryover is designed by using Matlab,and the program is used to ensure the rotor nonundercutting and non-carryover.The influence of geometric parameters on the rotor area utilization coefficient is analyzed.Three-dimensional numerical simulations of the novel twolobe,three-lobe elliptical rotor and twisted arc rotor are conducted.The pressure field,temperature field,velocity field and its working process of the rotor are obtained.The influence of the geometric parameters on the average flow rate of the novel elliptical rotor is analyzed.The structure of the novel segmented Roots rotor is designed,and the numerical simulation of the two-lobe segmented,three-lobe segmented rotor with different angle combinations are conducted by using Pumplinx.The influence of angle combination on the performance of segmented rotor is researched,and compare the segmented rotor with the traditional circular arc and twisted-arc rotor.The results show that the area utilization coefficient and flow rate of the elliptical rotor is inversely proportional to elliptical axial ratio ?;the average flow and area utilization coefficient of the elliptical rotor is higher than circular arc rotor.Compared with the circular arc rotor,the angle combination of 0o-30o two-lobe and two-segmente rotor,the angle combination of 0o-30o-60o two-lobe and three-segmente rotor,the angle combination of 0o-20o three-lobe and two-segmente rotor,the angle combination of 0o-20o-40o three-lobe and three-segmente rotor can not only greatly reduce the flow rate pulsation and pressure pulsation at the outlet,but also improve the average flow rate,so it has better performance.This paper provides a powerful theoretical basis and reference for the design of Roots rotor and improving the operating efficiency and stability of vacuum pump.