Simulation Calculation Of Clearance Inside The Chamber Of Twin Screw Vacuum Pump

The deformation inside the chamber of screw vacuum pump during operation is calculated by means of ANSYS software. The temperature distributions and deformations of the rotors are obtained by coupling heat and force boundary conditions. Both the axial and radial deformations between rotors in several important cross-sections are given, and so are the clearances between rotor and chamber. The Calculation results indicate that due to its complex geometrical construction, the deformations of the rotors are very complicated and change in different cross-section. Therefore, the clearances between the two rotors and the clearances between the rotor and chamber must be changed correspondingly according to the deformation to avoid rotor stuck.In this paper, computational fluid dynamics (CFD) method was used to study leakage through the addendum circle clearance by means of CFX software. The results of the research shows:(1) The temperature of gas has notable influence on the mass flow through addendum circle clearance. This kind of influence will be more remarkable on exhaust end. And the particularly low gas temperature will intensify the leakage.(2) The leakage through the same high clearance decreases with the increase of clearance width. The speed of the decreasing has a tendency to slow down gradually, but overall, the leakage is linear with respect to clearance width. Comprehensive consideration of space between teeth, leakage through addendum circle clearance, dynamic balancing and other factors will be needed in practical design of clearance width.(3) The leakage through the addendum circle clearance is direct ratio to clearance height under the same pressure difference. But the relationship between them become no longer linear with corresponding different pressure difference. And the disparity of two leakage curve decreases with the increase of clearance height. On suction side addendum circle clearance, the leakage decreases significantly with clearance height reducing from0.5mm to0.3mm, but the decreasing is not obvious when height down from0.3mm to0.2mm. On exhaust side, the leakage decreases more and more rapidly with clearance height down to0.2mm. So the addendum circle clearance height during operation should be less than0.3mm.The study of this paper provides simulant calculation method and theoretical basis for design and optimization of clearances inside the twin screw vacuum pump, which has positive significance on improving the pumping performance.