Analysis Of Rotor System Dynamics Of High-speed Small Compound Molecular Pump

Compound molecular pump is a kind of momentum transport vacuum pump applied in high vacuum and ultrahigh vacuum field.It has advantages of big pumping speed,high compression ratio,and can get clean vacuum.As a kind of high speed rotary machinery,the speed of pump’s rotor can come to 20000-90000 rpm,such a high speed is a basic requirement to obtain good pumping performance,also inevitably bring dynamics problems like vibration and rotor system stability.For high-speed small compound molecular pump,the small clearance between turbo blade and static blade,rotor drag and stator drag exacerbate the failure strength and the difficulty to solve these problems,becoming the main factors that restrict the localization,and at present,the high-speed small compound molecular pump products applied in high-end leak detector and mass spectrometer filed still need to import.Therefore,it is important and meaningful to discuss the rotor system dynamic characteristics of compound molecular pump,especially the high-speed small compound molecular pump which is badly needed in China.For this purpose,the rotor system of FF-63/80 type compound molecular pump is studied as the research object,and the dynamic characteristic is studied by using simulation method.Firstly,3D geometry model of the rotor system is established by Solidworks modeling software,and the dynamic characteristic is calculated by the ANSYS Workbench finite element analysis software,which mainly includes:(1)Using Modal analysis module,get the natural frequency of rotor system,and then calculate the critical speed,the results show that,rotor system works beyond the 2th critical speed,therefore,the risk of resonance exist;The contours of rotor system main vibration shape are obtained,then analyze the deformation shape and relative size,and judge the security risks existing in current structure;Discuss and obtain the effect rules of bearing stiffness and inherent characteristics,and then put forward suggestions and methods to improve the inherent characteristic by adjusting bearing stiffness.(2)Using Harmonic Response analysis module,discuss and obtain common axial force and torque effects on rotor system stability and high pressure effects on reliability of rotor blades,the results show that,three kinds of loads and deformation of observation position show changes in index,further analysis find that the axial force has little influence on the stability of the rotor system,while the torque is more obvious,and high pressure effects on the dynamic reliability of blades is significant.(3)Using Transient Structure analysis module,discuss and obtain the effect rules of acceleration on the stability of the rotor system,the results show that,the start of rotor system is a process of oscillation and then gradually tend to stable,the trend of oscillation amplitude and time required for stable shows opposite,and both of them affected by the acceleration,therefore,reasonably choose the acceleration can make accelerating process more quickly and smoothly.Through further analyzing the influence factors of acceleration,put forward several measures to improve the stability of rotor system.Through the analysis above,obtains comprehensive dynamics characteristics of rotor system both in static,steady-state and transient conditions,main results agree with fund cooperation partners,fully illustrates the rationality of model process in this paper,as well as the feasibility and reliability of simulation method in compound molecular pump rotor dynamic research field.At the same time,compared with conventional test method,this method is more efficient and less cost,and it is worth to promote.