Pumped storage units are the main parts in China’s power construction, as a hot issue concerned by the industry. The pump turbine involves the two-way flows and a multiple condition operation, and its operation flow pattern is very complex. The particle image velocimetry (PIV) is a very effective test technique to determine the internal flow field of pump turbines. This paper discusses the key problems of the pump turbine, based on the PIV experiments under typical conditions of the pump turbine, especially for problems such as the S-shape problem, the hump problem, the pressure fluctuation problem and the cavitation problem. In the internal flow fields under typical conditions are determined. The vortices induced and their development are observed in the PIV test. The flow phenomenon is shown at each operating point. The typical problems of the pump turbine are closely related to the vortex distribution in the internal flow field. From the PIV test results under several working conditions and from the comparisons between the optimal condition and the part load condition, it is seen that the vortex distributions are very different. Vortices at the vane-less area between the guide vane and the runner are closely related to the strong pressure pulsation, the first hump and the S-shape curve. From the PIV results of the cavitation working points, it is seen that the flow angle is changed in the vane-less region and the runner leading edge because of the cavitation bubbles and that the flow angle deviates from the optimal setting angle. From the computational fluid dynamics (CFD) result of the second hump working points, it is concluded that the vortex shedding on the runner leading edge is the main cause of the second hump.

抽水蓄能机组是我国电力建设的主要部件，是业界关注的热点问题。水泵透平涉及双向流动和多工况运行，其运行流型非常复杂。粒子图像测速法（PIV）是一种非常有效的确定水泵涡轮内部流场的测试技术。本文基于水泵水轮机典型工况下的PIV实验，讨论水泵水轮机的关键问题，特别是S形问题、驼峰问题、压力波动问题和汽蚀问题。在典型条件下的内部流场是确定的。在 PIV 测试中观察到产生的涡流及其发展。流动现象显示在每个操作点。水泵涡轮的典型问题与内部流场中的涡流分布密切相关。从几种工况下的PIV测试结果以及最优工况和部分负载工况的对比可以看出，涡流分布有很大的不同。导叶与转轮之间无叶片区的涡流与强压力脉动、第一驼峰和S形曲线密切相关。从空化工作点的PIV结果可以看出，由于空化气泡，无叶片区域和转轮前缘的流动角发生了变化，并且流动角偏离了最佳设定角。从第二个驼峰工作点的计算流体动力学（CFD）结果，