Research On Pumping Performance And Test Method Of Different Roots Rotors For Multi-Stage Dry Vacuum Pump

By serially integrating different type of rotors,the multi-stage dry vacuum pump can realize different requirements of ultimate pressure and pumping speed,and multi-stage dry vacuum pumps are widely used in the semiconductor industry,chemical equipment industry,film manufacturing industry et al.At present,in order to improve the pumping performance of multistage dry vacuum pumps,vacuum pump manufacturers and research institutes have carried out extensive and in-depth researches on the pumping principle and upgrade design of multi-stage vacuum pumps.However,the existing research mainly focuses on the structural optimization and performance evaluation of a certain rotor,and the current test methods of dry vacuum pumps are only for pump products,the systematic study of multi-stage dry vacuum pumps and the pumping performance research of different rotors are still in the initial stage.This paper aims to further explore the difference pumping performance of different rotors in multi-stage dry vacuum pumps,and obtain the pumping performance test and evaluation methods of different rotors of multi-stage dry vacuum pumps under real operating conditions.In this paper,different types of rotors in multi-stage dry vacuum pumps are taken as research targets.According to the principle of rotor conjugate meshing,the profile models of two-roots,three-roots,five-roots rotor are established.The MATLAB simulation analysis platform is used to complete the rotor profile programming.In addition,based on the pumping principle of the roots pump,the theoretical pumping speed of different number of roots rotor lobe is discussed.It can be known that with the increase of rotor shape coefficient c=Rm/R,the volume utilization coefficient and the pumping speed of the Roots rotor also increase.Under the same rotor shape factor,the theoretical pumping speed of the Roots rotor increases with the number of roots lobe,but for the two lobes,three lobes and five lobes roots rotor,the maximum values of the rotor shape coefficients are 1.6698,1.4770,and 1.3128,therefore,the more the lobes of roots rotor,the smaller the theoretical pumping speed can be.In addition,Fluent flow field analysis software was used to research the pumping performance of common suction-stage roots rotors(two-lobes and three-lobes roots rotor)and exhaust-stage roots rotors(three-lobes and five-lobes roots rotor)of multi-stage dry vacuum pump.It is known that when the roots rotor is used as suction stage rotor,both the two-lobes and three-lobes roots rotor can achieve a high pumping speed,but the pressure distribution of two-lobes roots rotor is more unevenness,and the local position vortex is more obvious,which resulting in greater noise and vibration during operation.When the roots rotor is used as exhaust stage rotor,the pumping speed of three-lobes roots rotor is higher than that of the five-lobes,but the internal pressure distribution of three-lobes chamber is not as uniform as that of the fivelobes roots pump,which is not conducive to the treatment of large load gas during the exhaust process.The five-lobes roots rotor can achieve better running stability.Finally,a test method is proposed for pumping performance test of the single-stage or multi-stage,and an integrated adjustable test pump is developed for the performance comparison.Through the ANSYS Workbench simulation analysis platform,the thermalstructural coupling analysis of the shaft design and rotor structure is carried out and obtain the deformation and stress distribution of key components.Based on the simulation results,combined with actual engineering experience,the bearing clearance,the gap between the rotor and other fitting tolerances were determined,and the drawing engineering and manufacturing of the overall scheme was carried out.The development of the adjustable test dry vacuum pump provides a verification method for the testing of the pumping performance of different Roots rotors,and provides new ideas and methods for the performance test of the dry vacuum pump in the research and development stage.In summary,the theoretical analysis of the pumping performance of different Roots rotors of multi-stage dry vacuum pumps is carried out.The internal flow field of different Roots rotors is completed by Fluent numerical simulation.Besides,a new test method is proposed for single or combined-stage test of different rotor pumping performances in multi-stage dry vacuum pumps,at the same time,an experimental vacuum pump with adjustable rotors is developed for different rotor designs,which provides a simple and feasible solution for integrated measurement of different rotors.By researching pumping theory and test methods,this paper provides a theoretical basis and reference means for the research and development and design optimization of domestic multi-stage vacuum dry pumps.