Flow Field Investigation On Roots Pump

Roots vacuum pumps have the advantages of large pumping speed and quick starting as the pressure in a wide range, and they are widely used as a booster in metallurgy, chemical industry etc. Now, researches to Roots pump have focused on type line theory and CAD design. The researches, basing on the pumps’ working processes, using CFD (Computational Fluid Dynamics) programs, are less. In this paper, CFD method is used to study and analyze the Roots pump flow characteristics in flow field, and the model simulated the effect of adding counter-current cooling.Firstly, using three-dimensional software to build the geometric model of Roots vacuum pumps. The whole model is divided into suction port, exhaust port, the pump chamber of three parts, establishing the three-dimensional model with the actual size in accordance. Upon completion of the geometric model, establishing grids for the corresponding model using ANSYS_ICEMCAD software, and setting the grid parameters, adjusting the grid quality. Meshes in suction port and exhaust port are tetrahedral, while in the pump chamber part are maked hexahedral mesh using the O-grid Methods Subsequently, putting the grid into CFX software, setting up various domains, establishing boundary conditions and initial conditions. Using interface surface to transfer, For different domains, and using external Fortran program to control the rotating and changing position of the grid in internal of pump, and using RNG κ-ε turbulence model to simulate,and obtaining the parameters of the corresponding.After simulating, we will view the RMS of the data with the software, to determine the convergence of the results. Then, observing periodicity of the data curve to determine the stability of the results, and then, comparing the simulated data with the real values to determine the validity of the model. The specific method is to calculate the pumping velocity value according to the results of simulation under different inlet pressure. Then, pointing at the pumping velocity curve provided by factory, observing the degree of the integration of the points and curves.After determining the reliability of the results, we analyze the work process of during the single-side-rotor rotating from0degree to180degree, including the pressure, temperature, and velocity condition in the flow field, and then,analyze the situation when the exhausting flow achieve the maximum and minimum, and we will obtain the reason of the exhausting flow pulsation.Finally, we set the counter-current cooling near the outlet part of roots pump, and simulating use the same condition of the previous simulation, and then, analyzing the results of the simulation, comparing the pressure and the velocity curves for after and before to determine the influence of roots pump pulse of exhausting flow rate for adding the counter-current cooling.This numerical simulation method could be used as a reliable analytical tool for the flow in the actual operation of roots pumps.