Transient Flow Simulation On Roots Dry Pump

Dry vacuum pump is widely used in aerospace, semiconductor, chemical and pharmaceutical industries. With the continuous expanding vacuum application in the production, the performance requirements of vacuum pump have gradually increased. At present, the research of dry vacuum pump mainly focuses on improving the accuracy of production and processing, optimizing rotor profile and calculating clearance leakage. Investigation on gas flow inside vacuum chamber using CFD simulation will clearly reflect the flow characteristics, reveal the flow essence, and effectively predict the performance, to solve practical problems; this research is rare so far. Based on one Roots dry vacuum pump chamber as target this paper simulates and investigates internal transient flow field.First, this article establishes three-dimensional model of Roots pump chamber by designed size, and generates structured and unstructured mesh separately according to the different gird movement. It introduces RNG k-ε turbulence model on combined model, sets solve parameters followed actual situation. Tow dynamic grid strategies are introduced on chamber flow zone, the external FORTRAN programming language controls the update of grid deformation, achieving the deformation simulation of pump chamber.Second, it studies the pressure and velocity cyclical fluctuations of flow simulation result after comparing with actual pumping speed curve to verify the accuracy, describes gas flow inside pump chamber and basic reason of vortex generation and disappearance, and analysis the distribution and variation of chamber pressure, temperature field.Finally, it simulates dynamic heat transfer process of Roots rotor in ANSYS multi-physics by indirect coupling method based on the chamber flow transient simulation result, and studies rotor thermal deformation and its effect on clearance size of pump chamber.