Investigation On Traction-stage Pumping Characteristics And Structural Optimization Of High-speed Small Compound Molecular Pump

In recent 20 years,with the rapid development of semiconductor,pharmaceutical,aerospace and other industries,the demand for molecular pump which can get clean high vacuum equipment are increasing.Compound molecular pump with high pumping speed,high compression ratio and other advantages,has become a hot vacuum obtaining equipment.At present,the high-speed small compound molecular pump applied in high-end mass spectrometer and leak detector,are still mainly imported.Therefore,it is necessary to develop a domestic high performance small compound molecular pump.Based on the ministry of science major equipment projects,the traction-stage performance and structure optimization of F-63 type compound molecular pump were studied.Firstly,the calculation model of single-stage and multi-stage turbine blade pumping performance,multi-groove cylinder traction stage and disc transition stage were established.Then we programed the design and calculation of compound molecular pump,to improve the computational efficiency.On the basis of a large number of calculations,the relationship between the traction stage compression ratio and traction angle,spiral groove depth,rotor-stator gap,spiral groove width,rotor speed and other factors were found,which provides a solution for the optimization design of traction tube.We proposed some structural optimization programs.Such as reduced return flow structure,traction cylinder for sectional processing,angle tilt tractor,forward and reverse spiral groove.The influences on the performance of structure optimization were studied.The transition structure was put forward to solve the low pumping efficiency problem between turbine stage and the traction stage of the compound molecular pump.The working principles of three kinds of transition structures were studied.The transition structures are disk transition structure,short tooth transition structure and large spiral groove.The effect of transition structures on the pumping performance of the original molecular pump was discussed.By contrast,the disk transition structure is more suitable for F-63 composite molecular pump,and can greatly improve the pumping performance.The modal analysis of the rotor system with transition structure was carried out,to investigate the influence of transition structure on the whole rotor system.We obtained the natural frequencies and the main modes of the first 6 orders.Through the critical speed analyzing,found the working speed of the rotor is between the 3rd and 4th order critical speed,and there is no risk of resonance.This paper presents some improved scheme for F-63 compound molecular pump prototype structure.In accordance with national standards for testing,the pumping speed,compression ratio and other properties of the new pump has improved significantly.