高水头混流式水轮机的动静干涉与振动问题研究

Analysis of rotor-stator interaction and vibration in high-head Francis turbines

针对小天都1号混流式水轮机运行中高频振动的问题,本文采用真机试验和数值计算的方法,研究了水轮机无叶区的动静干涉及蜗壳水力激振频率。在真机试验中,主要分析了机组的振动、水压力脉动的幅值和频率特性,同时利用数值计算进行全流道非定常计算,模拟了活动导叶与转轮之间的动静干涉,详细分析了蜗壳与无叶区的压力脉动特性,两者共同证实机组的异常振动是由于动静干涉引起的。其次,针对现场试验中机组出现的振动问题,从产生共振的条件出发,提出了最佳叶栅组合、降低了无叶区的压力脉动,为水电站减振降噪提供了可实施方案。

This paper describes a study on rotor-stator interaction （RSI） and frequencies of flow-induced vibrations in the spiral casing of a high-head Francis turbine unit #1 at the Xiaotiandu hydropower station, using prototype tests and numerical simulations. The tests were aimed at the amplitude and frequency of pressure fluctuations and vibrations, and whole passage simulations of unsteady turbulent flows were focused on an analysis of the RSI between the guide vanes and runner and a detailed examination on pressure fluctuations in the spiral casing and vaneless space. Both the tests and simulations verified that RSI had induced abnormal vibrations in this turbine unit. We analyzed the RSI effects produced by different combinations of runner blade number and guide vane number to solve the problem of vibrations observed during the field tests. Through an analysis on resonance conditions and by applying the principle of optimally matching these two cascade systems to the results obtained from the combinations, we developed an effective method for reducing pressure fluctuations in vaneless space. The results would provide a practically feasible scheme for vibration and noise reduction at hydropower stations.