Structure Design And Research On The Key Techniques For Twin-screw Vacuum Pumps

Dry screw vacuum pumps have been widely used in many industrial and scientific fields for its remarkable advantages such as producing of oil-free vacuum, adapting for the mal-condition and discharging directly into atmosphere. Gas compression and transportation of this pump can be achieved by the invasion and reduction of the tooth cavity volume while pump is rotating. The pumping performances of the pump are greatly determined by its rotor profiles. As lack of extensive and systematic research of the rotor profiles in our country, the independent design and fabrication of the pump becomes difficult.In this paper, the equation of the contact line of newly designed twin-screw rotor profiles is derived, and a new method to deal with the problem is also put forward by means of MATLAB. The dynamic balance property of the rigid screw rotor is analyzed with three methods, and the full dynamic balance can be achieved by means of spiral removal of the rotor material. Considering the difficulty of actual processing, two kinds of self-balance rotor are designed. Based on the mathematical model built, the change of gas state and the characteristic of back flow leakage in the chamber are studied. The thermal deformations of the rotors are simulated and suitable gaps are suggested. The minimum lead number of the pump is given according to the axial displacement process of gas in the complete seal chamber. The optimization design of the rotor parameter and the pump structure is given under certain pumping speed. The paper provides a theoretical reference for the overall design of screw pumps and the analysis of the character of the rotor and its work process.