Flow calculation in the spiral grooves of a vacuum pump in the high pressure regime

• Main Authors: Shiauh-Pirng Jung, 鍾孝平
• Other Authors: Yeng-Yung Tsui
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/07116201403034295017

碩士 === 國立交通大學 === 機械工程系 === 90 === In this thesis, CFD is used to analyze viscous flow of dynamic meshes in spiral grooved vacuum pumps with ALE method. Unstructured and nonstaggered meshes are adopted in computations. The SIMPLE algorithm is taken to couple velocity-pressure relations and the governing equations are discretized by finite volume method. For avoiding checkerboard from nonstaggered meshes, we correct mass flow with a Rhie & Chow method. Besides, a throughput of the pump is obtained by fixing the inlet and outlet pressure, and a special treatment of velocity-pressure couple is necessary for the pressure boundary in the inlet. In this thesis, a spiral grooved vacuum pump [9] is analyzed and we explore the pumping performance in the laminar flow mainly. Different design parameters are tested how to influence the pump throughput. Testing on spiral angle and channel height indicates that these parameters need to be optimized to achieve better performance. The appearance of clearance leads the gap leakage and the pumping performance is becoming worse with increase of the clearance. When number of channel is fewer, influence of the gap leakage is lowered and the throughput increases with reduction of number of channel. Results also reveal that increase of rotating speed transfers more momentum into fluid and the larger throughput is obtained. As regards turbulent flow computations, the linear κ—ε model and wall-functon are incorporated to solve. The difference of computation and experiment is possibly due to the use of high Reynolds turbulent model. To overcome this problem, a low Reynolds one is adopted to solve but the complexity of numerical model is also increased. This problem is still needed to solve.