The Analysis Of Multiphase Flow In Adjacent Flow Region Of Multi-Stage Roots Dry Vacuum Pump

The chief features of Multi-stage Roots dry vacuum pump are the wider range of working pressure, discharged directly to the atmosphere, the low maintenance costs, the high pumping speed, etc. Therefore, it is widely used in semiconductor, pharmaceutical, metallurgy, petrochemical and aerospace industries. In PECVD or etching process, a Multi-stage Roots dry vacuum pump are often faced with complex and harsh work condition. For example, the corrosive gases, solid particles and the presence of temperature and pressure pulsation, even in the pump chamber, there are complex physical changes and chemical reactions. Therefore, it is significant to maintain the comprehensive performance of a multi-stage Roots pump while working in harsh conditions. This article took several groups of numerical simulation in adjacent stages’flow field into a Multi-stage Roots pump by the method of computational fluid dynamics. In addition, the results of calculation are analyzed and compared.Firstly, this article finished creating the geometric model of adjacent stages’flow field into the Multi-stage Roots dry vacuum pump by Solidworks and meshing each part according to the geometric and motion characteristics. Using external Fortran program, two different method were used for the grid update of the rotor-rotor and rotor-pump chamber included in the flow region to control the movement of the grid nodes and thus realize the dynamic grid simulation.Secondly, according to the basic theory of multiphase flow, with Euler-Lagrangian method, this article simulated gas-solid two phase flow at atmospheric pressure in the adjacent stages’flow field of the Multi-stage Roots pump by ANSYS CFX and got some convergent simulation results. According to these results, this article analyzed the movement law, trace features, passing-depositional feature of the particles injected into the flow field, compared the effects of two calculation methods (one-way coupling and fully coupling) to the simulation results and verified the conformance of numerical simulation results and dilute phase flow theory.Finally, based on different pumping conditions that Multi-stage Roots dry vacuum pump faced in practical work, multiple groups of comparative numerical simulation were taken in order to contrast such four impact factors:particle diameter, interaction between particles and wall, pressure-compression ratio and wall roughness. Deposition characteristics of the solid particles in the pump was analyzed in order to provide references for Multi-stage Roots dry vacuum pump improvement and optimization in engineering practice.