Cavitation characteristics of axial-flow pump based on modified partially-averaged Navier-Stokes model
YU Yunyun1*, ZHOU Daqing2, YU An2, LIU Jiajia3
1. Jincheng College, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 211100, China;2. College of Energy & Electrical Engineering, Hohai University, Nanjing, Jiangsu 211100, China; Yangzhou Branch of Jiangsu Water Source Company Ltd. of the Eastern Route of the South-to-North Water Diversion Project, Yangzhou, Jiangsu 225000, China
Abstract：In order to study the cavitation problem of axial flow pumps, the secondary development technology of CFX software was used to modify the turbulence model, and realize the dynamic definition of the parameter fk in the PANS model by writing CCL language, so that it can be defined according to local grid conditions and turbulence lengths. The revised turbulence model was used to numerically calculate the cavitation in the entire flow channel of the axial-flow pump. According to the calculation results, the critical NPSH of the axial flow pump was 5.37 m. The test shows that the actual critical NPSH is 5.68 m, and the error between the two is caused by the test conditions and the test system, and is within a reasonable range. And the reliability of the turbulence model in the cavitation calculation of the axial flow pump was also verified by taking the cavitation diagram in the test. By analyzing the numerical calculation results, the cavitation characteristics of the axial flow pump under different working conditions were obtained. As the decrease of NPSH, the volume fraction of cavitation in the impeller of the axial flow pump increases, the vorticity increases, and the surface pressure and flow velocity of the blade fluctuate correspondingly at the position where the cavitation occurs and collapses. With the increase of flow rate, the critical NPSH of axial flow pump decreases, the overall amount of cavitation distribution becomes larger, the value of turbulent kinetic energy inside the impeller becomes larger, and the turbulent flow dissipation becomes serious, which is directly related to the occurrence and collapse of cavitation.
