Methodology for generating a general profile of asymmetrical rotors of twin-screw vacuum pumps with point meshing feature by a pre-defined sealing line

Abstract

The sealing line is one of the key influences on twin-screw rotor vacuum pump performance. The design of a rotor profile based on a sealing line for an asymmetrical rotor of a vacuum pump can be studied further to generate varied rotor profiles and improve pump performance. Therefore, this study proposes a mathematical model for a pre-defined sealing line to design and optimize varied rotor profiles of vacuum pumps. The general sealing line, pre-defined by explicit equations of straight lines and elliptic curves, is proposed to generate various rotor profiles with different numbers of lobes. The functions for parameter variables of the pre-defined sealing line are constructed and directly variated along the rotor length to form the screw rotor with a variable pitch and a variable cross-section. The proposed pre-defined sealing line is also applied in the optimal design of a rotor profile to enhance pump performance. Numerical examples are performed to verify the flexibility and practicability of the proposed method.