Abstract:
In the current work, pumping speed measurement of three-vane rotary vacuum pump is discussed in detail using both experimental and numerical approaches. Performance parameters of an air cooled, dual stage and rotary three-vane vacuum pump with high compression ratio are discussed here. Performance tests of the pump are performed for its different parameters, such as pumping speed, working temperature, ultimate pressure etc. In vacuum pumps, pumping speed, defined as volume flow rate / capacity of the pump, is the main performance parameter. The vane pump is tested using three assessment systems: flow meter method, intermittent pump down method, and continuous evacuation method, which are constructed according to DIN and ISO standards. Since continuous evacuation method is not recommended for measuring pumping speed due to thermal issues, improvements in the technique are suggested in this work. The suitable numerical methodology is also described for measuring the pumping speed of the vane pump. Pumping speed is predicted here only for the continuum flow (Knudsen number < 0.1) for which Navier-Stokes equations are applicable. Commercial computational fluid dynamics software package is used to numerically solve the governing equations. Moving/dynamic mesh technique is used for the internal flow volumes of the pump to reproduce the change-in-time shape. Complete process starting from CAD modeling to CFD simulations is discussed in detail. The adopted approaches are generic and can be used to find the pumping speed of any other rotary vane vacuum pump. Comparison of experimentally measured and numerically calculated volume flow rate in the continuum flow regime reveals the accuracy of the calculations.
