Numerical simulation of different blade tip clearances on internal flow characteristics in mixed-flow pump
ZHANG Desheng1*, SHEN Xi1, DONG Yaguang1, WANG Chaochao1, LIU An1, SHI Weidong2
1. National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu 212013, China; 2. School of Mechanical Engineering, Nantong University, Nantong, Jiangsu 226019, China
Abstract：To investigate the effects of tip clearance on the performance and unsteady flow in the mixed-flow pump, four sizes of tip clearances, 0, 0.25, 1.00, 2.00 mm, were selected to conduct simulation calculation based on SST k-ω turbulence model. The pressure difference distribution, lea-kage flow rate, inlet axial velocity distribution and tip leakage vortex rotation intensity were analyzed. The results show that the leakage of the model pump from impeller inlet to impeller outlet shows a ten-dency of increasing first and then decreasing under different operating conditions, which is the same as the variation trend of pressure difference in the clearance. With the increase of the gap size, the lea-kage of the blade tip also increases, which leads to the increase of the energy loss of the pump. It is found by comparison that the clearance size is the main factor affecting the leakage. Under the part-loading conditions, the rotation intensity of the leakage vortex formed by the interaction between tip blade leakage flow and main flow gradually increases with the increase of blade tip clearance.Part of leakage flow enters the passage of adjacent blades, leading to flow instability. As a result, the energy loss and flow instability of the pump show an increasing trend with the increase of gap size. With the increase of flow rate, the rotation intensity of tip leakage vortex gradually decreases at different clearances.
