PIV measurement and numerical calculation for impeller inlet flow field in axial flow pump
Zhang Hua1, Shi Weidong1, Chen Bin2, Zhang Desheng1, Shao Peipei1
1.National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu 212013, China; 2.Research Institute of Chemical Machinery, Hefei University of Technology, Hefei, Anhui 230009, China
Abstract：The internal flow field for axial flow pumps is complex, especially the tip leakage in the end-wall region. This phenomenon can not only disturb the flow field at impeller inlet, but also play an important role in the flow within impeller passage. Therefore, the flow field close to impeller inlet was investigated using an approach combining CFD numerical method with the PIV measurement system to reveal the flow mechanism. The results of PIV show that: the distributions of streamlines and velocity contour are relatively uniform at 1.2Qopt and 1.0Qopt conditions, while at 0.8Qopt condition, a region with low velocity appears near the outer wall close to blade leading edge and the streamlines deflect to hub-side. Numerical results reveal that the predicted pump performance curves agree well with the experimental results, and the flow field at impeller inlet is consistent with the PIV results. Moreover, it is found that the flow direction in clearance for 5% blade tip height at 1.2Qopt condition is as the same as that for mainstream. For the case of 1.0Qopt, fluid within tip clearance mainly migrates along the circumference direction. Tip leakage flow arises as the flow rate decreases to 0.8Qopt, with separation phenomenon followed by adhesion in the clearance close to pressure surface side, forming a counterclockwise vortex due to the effect of collision and entrainment of leakage flow and mainstream on suction surface side.
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