The Analysis Of Flow Characteristics For The Multi-Stage Roots Dry Vacuum Pump

Multi-stage Roots dry vacuum pump is a high-speed rotary volumetric dry vacuum pump, and it through volume change caused by high-speed rotation of the rotors in the each stage pump chamber to work. The chief features of this kind of vacuum pump are the wider range of working pressure, the higher pumping speed at the higher pressure, the higher maximum fore pressure, the cleaner vacuum environment, the severer design, faster startup and maintenance costs less low. Currently, the types of vacuum pumps have been widely used in a number of industrial areas, such as petrochemical, light industry, papermaking, electronic industry and food processing.This article simulated the flow field in the multi-stage Roots dry vacuum pump with computational fluid dynamics software CFX, and includes the processing and analysis of simulation results.First, this paper used the CAXA and Solidworks modeling software build the three-dimensional solid model of the pump chamber and all levels of the junction flow field according to the structural parameters of the multi-stage roots dry pumps and Roots rotor profile equations.Secondly, according to the requirements of the different regions of the model grid characteristics, the paper meshed this model with hexahedral structured grid and tetrahedral unstructured mesh. For the moving grid of Pump cavity, during the simulation the paper used the CFX-Solver to call the FORTRAN programs with spring smooth approximation method.Later, the paper set pre-processing part and boundary conditions according to the actual working conditions, and used CFX-Solver software to solve it in order to get the stability and convergent simulation results. And the paper analyzed accuracy and pulsating characteristics of the simulation results.Finally, the paper used the CFX-Post as the processing software to analyze the velocity distribution law and the cause of the flow field changing process in the process of rotor rotation. In addition, the paper analyzed the internal pressure and temperature field distribution and changes in the course of vacuum pumps work. The distribution and changes of physical quantities in each stage flow field were compared and researched in this paper.