Abstract:Concerning the safety and stability in operation of Roots pumps which are featured with large flow rate and high speed, the topology of lobe in a two-lobe Roots pump was optimized by means of e-volutionary structural optimization(ESO)method. Since a structural mutation phenomenon occurs du-ring the optimization process, the screening and deletion algorithms are proposed based on the connection traits between singular elements to improve the ESO method, eventually the stability and continuity of the optimization process are ensured. The improved ESO method was realized by using Ansys mechanical parametric design language(APDL). At first, the allowable interval of initial rejection rate was ascertained by using interval approximation and combining with the visual process of program. Then, the topology of lobe in a two-lobe Roots pump was optimized with five kinds of initial rejection rates when it was subject to the 1 500 r/min inertial load. Finally, a reasonably topological structure for the lobe was decided by analyzing maximum stress, strain and displacements in different design cases and sifting among them. Comparing the results of finite element analysis shows that the optimized structure not only experiences more even stress distribution under the inertial load but the material utilization ratio is also improved considerably. The maximum stress, strain and displacement are reduced by 17.7%, 17.5% and 18.7%, respectively, the mass of rotor is decreased by 55%; as a result, the safety and stability can be improved greatly for this Roots pump operating at a high speed and large flow rate.
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