Abstract:Tip cavitation in a scaled axial-flow pump is simulated by using a partially-averaged Navier-Stokes(PANS)model and Zwart cavitation model at a rated flow rate and under a specific NPSH. The numerical results are compared with the experimental data made by making use of high-speed photography. Different types of tip vortex cavitation and leakage vortices are exploited, and the locations where cavitation in tip leakage vortex core is mostly prone to occur are identified; the cavitating flow fields at various dimensionless chord lengths are analyzed as well. The simulated pump cavitation performance curve agrees so well with the experimental data that the largest error is 5.8% only. The tip leakage vortex core has the maximum vortex intensity coefficient and minimum pressure coefficient at a dimensionless chord length of λ=0.30~0.35, indicating a location where cavitation is mostly pronounced to emerge based on vorticity method. Based on the method, the vortex center is defined as a point with the maximum vortex intensity. Due to the lowest pressure in the vortex core, the formation and development of cavitation in the tip region usually couples with the evolution of vortex structure. When migrating towards the pressure side of the neighboring blade, the tip leakage vortex will interact with the casing wall, resulting in counter-rotating vortex near the end-wall. At the trailing edge of blade tip, separated and induced vortices are generated, enhancing the instability of flow field between the impeller passages. As moving towards the neighboring blade pressure surface, the separation vortex can cause a change in blade loading distribution. As a consequence of increased leakage flux, the cavitation in the blade tip becomes more extensive, resulting in a severe degradation in the pump performance.
石磊, 张德胜, 陈健, 耿琳琳, 刘俊龙. 基于PANS模型的轴流泵叶顶空化特性[J]. 排灌机械工程学报, 2016, 34(7): 590-596.
SHI Lei, ZHANG Desheng, CHEN Jian, GENG Linlin, LIU Junlong. Analysis on characteristics of tip cavitation in an axial-flow pump based on PANS model. Journal of Drainage and Irrigation Machinery Engin, 2016, 34(7): 590-596.
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