高速潜水轴流泵大流量工况的空化特性

Cavitation characteristics of high-speed submersible axial-flow pump in high flow condition

为了研究大流量工况下高速潜水轴流泵的空化特性,基于ANSYS CFX软件,选取Zwart、Kunz以及Schnerr-Sauer 3种空化模型进行大流量工况下高速潜水轴流泵外特性和泵内空化流动特性数值模拟。结果表明:大流量工况下Schnerr-Sauer空化模型预测的外特性变化趋势与试验值最为吻合,相较于另两种空化模型,Schnerr-Sauer空化模型模拟的叶片背面空泡体积分数较高;空化严重区域主要出现在叶片背面进口附近以及叶顶,同一空化数下,流量越大,叶片空化状况越严重;叶片载荷分布由叶片进口边到出口边呈先增大后减小的趋势;各流量下空泡首先出现在叶片背面进口前缘位置,随着空化数的减小,空泡体积分数沿着主流方向朝叶片后缘不断增大直至空泡占据整个叶片背面;叶片背面处的三角形云状空化尾缘空穴极不稳定,随着叶轮旋转,尾缘处空泡微团逐渐脱落,朝着相邻叶片不断移动,对相邻叶片的工作面产生侵蚀破坏,导致叶片载荷发生变化,对轴流泵水力性能产生影响。

To study the cavitation characteristics of a high-speed submersible axial-flow pump in high flow conditions,three cavitation models including Zwart,Kunz and Schnerr-Sauer were selected and the external and the interior characteristics of the pump were simulated in high flow conditions based on ANSYS CFX.The results show that the prediction accuracy of Schnerr-Sauer model is most consistent with the experimental value in high flow conditions.Compared with the other two cavitation models,the volume fraction of bubbles on the suction surface of the blade is higher,and the area with serious cavitation mainly appears near the leading edge and at the top of the blade for Schnerr-Sauer model.The cavitation of the blades becomes more serious with the increase of flow speed at the same cavitation number.The load increases first and then decreases from the leading edge to the trailing edge of the blade.The bubbles generate at the leading edge of the suction of the blade at first and then expend to the trailing edge of the blade along the mainstream flow direction until occupying the whole blade suction with the decreasing of cavitation number.The cavities in the trailing edge of the triangle cloud cavitation at the back of the blade are extremely unstable.As the impeller rotates,the bubbles at the trailing edge gradually shed and move toward the adjacent blades,resulting in erosion damage and load change of adjacent blades,affecting the hydraulic performance of the axial-flow pump.