Study of the backward flow in Roots-type vacuum pump with elliptical rotor profile in the gas flow molecular regime

Abstract

A Roots-type two-rotor vacuum pump with the rotors’ elliptical profile was designed, developed and manufactured. Its channels conductivity was measured experimentally at various angles of the rotors’ rotation and pressures. Experimental conductivity of the channels was determined in the flow molecular regime. Using the angle factor method implemented in the COMSOL Multiphysics package calculated values of the channel conductivity were obtained for a two-rotor vacuum pump. Deviations in calculated data from the experimental data were not exceeding 10%. Verification and validation of analytical expressions for conductivity of the non-contact pump slot channels demonstrated possibility of their application in mathematical models of the working process of the two-rotor vacuum pumps.