Research On Working Performances Of Smooth Straight And Asymmetric Double-claw Rotors For Claw Vacuum Pumps

The claw rotor is the core component of the claw vacuum pump and determines its working performances.In order to solve problems of the unsmooth cusp and poor performances,the curve meshing theory is studied and three meshing models are established,including the model of arc and the equidistant curve of the epicycloid,line segment and its envelope curve,ellipse and its envelope curve.Based on the model of arc and the equidistant curve of the epicycloid,the smooth straight claw rotor is proposed.Based on the model of ellipse and its envelope curve,the asymmetric elliptic double-claw rotor is proposed.The meshing relationships and geometric parameters of the smooth straight claw rotor and the asymmetric elliptic double-claw rotor are studied.The profile equations are derived and the design program is obtained.The limit meshing point and undercutting discriminant are analyzed.Effects of the independent geometric parameters on the mechanical properties and working performances for the claw rotor are investigated.The working process of the claw vacuum pump is studied theoretically.The performances between the smooth straight claw rotor and the curved claw rotor are compared.A three-dimensional numerical simulation is conducted,and then the internal flow field of the asymmetric elliptic double-claw rotor vacuum pump is studied.The pressure changes and the mass flow of the suction port and discharge port are analyzed.The proposed smooth straight claw rotor realizes the smooth connection of the rotor profile and eliminates the mechanical wear and the stress concentration caused by the cusp.The proposed asymmetric elliptic double-claw rotor imporves its suction volume and working performances,expands the range of the discharge port.The geometric parameters of the proposed two claw rotors have the same influence on the performances.As the ratio of the radius on the claw top increasing,the relative carryover volume and the volume utilization factor increase,but the internal compression ratio decreases.As the arc angle of the claw top increasing,the relative carryover volume,the volume utilization ratio and the internal compression ratio decrease.As the ratio of the radius on the claw cusp increasing,the relative carryover volume increases,but the volume utilization factor,the internal compression ratio and the mechanical wear of the claw cusp arc decrease.Compared with the curve claw rotor,the smooth straight claw rotor has significantly advantages in working performances and mechanical properties.Through the pressure relief channel,the high pressure gas in the carryover mixes with gas in the suction chamber to avoid over-compression.The maximum leakage of the claw vacuum pump occurs in the meshing clearance of two rotors.Therefore,the research enriches the profile type of the claw rotor,reveals the flow field and its law of the double-claw rotor vacuum pump.It is of great significance to the research on the claw rotor and the claw vacuum pump.