In order to better understand the flow characteristics of mixed-flow pump with non-uniform tip clearance, a test rig is established and the flow fields of various cross section in impeller are studied based on particle image velocimetry technology. The velocity vector distributions of three cross sections, e.g., impeller blade inlet, middle and outlet, were measured. The influences of flow rate and eccentricity on the flow fields of mixed-flow pump with non-uniform tip clearance were analyzed, and the relative velocity distribution of different positions at the same cross section is quantitatively discussed. The results show that the external characteristics have been greatly affected by the eccentricity of impeller. There is a significant negative correlation between eccentricity and efficiency. The maximum head and efficiency drop of eccentric impeller reach 11% and 20% separately. With the increase in eccentricity, the secondary flow phenomenon increases, such as backflow and vortex flow in impeller flow passage. Vortex structure is easily formed in the end wall region, which will give rise to backflow and even blocks the flow passage near impeller hub. The energy loss increases continuously in this process which is the main reason for the significant drop in efficiency. The research results are instructive for revealing the flow characteristics of flow fields of mixed-flow pump with non-uniform tip clearance.

中文翻译：

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不均匀叶尖间隙混流泵流场的粒子图像测速测量

为了更好地了解叶尖间隙不均匀混流泵的流动特性，建立了试验台，基于粒子图像测速技术研究了叶轮各截面流场。测量了叶轮叶片入口、中间和出口三个横截面的速度矢量分布。分析了流量和偏心距对叶尖间隙不均匀混流泵流场的影响，定量讨论了同一截面不同位置的相对速度分布。结果表明，叶轮的偏心距对叶轮的外特性影响很大。离心率和效率之间存在显着的负相关。偏心叶轮最大扬程和效率下降分别达到11%和20%。随着偏心距的增大，叶轮流道内的回流、涡流等二次流动现象增多。端壁区域容易形成涡流结构，会引起回流，甚至堵塞叶轮轮毂附近的流道。在此过程中能量损失不断增加，这是效率显着下降的主要原因。研究结果对揭示叶尖间隙不均匀混流泵流场的流动特性具有指导意义。这会引起回流，甚至堵塞叶轮轮毂附近的流道。在此过程中能量损失不断增加，这是效率显着下降的主要原因。研究结果对揭示叶尖间隙不均匀混流泵流场的流动特性具有指导意义。这会引起回流，甚至堵塞叶轮轮毂附近的流道。在此过程中能量损失不断增加，这是效率显着下降的主要原因。研究结果对揭示叶尖间隙不均匀混流泵流场的流动特性具有指导意义。