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一、前言最近,水轮机和水泵水轮机极力采用高转速,又在大量建设的地下式抽水蓄能电站中,因机组安装高程很低,而且尾水道水位大幅度变动,以致向尾水管补气有困难,因此吸出高度对部分负荷时振动特性的影响成了新问题。大家知道,混流式水轮机偏离最高效率点运行时,在转轮出口就有旋涡流动,而在尾水管上部的中心产生强制涡流中心。由于涡流中心内部压力低,在σ小时,强制涡流中心就引起汽蚀,而在中心区域形成空腔。特别在部分负荷运行时,强制涡流中心大为发展,其中心区的汽蚀空腔在尾水管内部作周期性的偏心摆动,形成涌浪现象。但是关于强制涡流中心和涌浪
I. INTRODUCTION Recently, turbines and pump turbines struggled to adopt high speed, and in a large number of underground pumped storage power stations, due to the low installation elevation of the units and the drastic changes in the water level of the tailrace, it is difficult to supply air to the draft tube , The effect of suction height on the vibration characteristics at part load has become a new problem. As you know, when the Francis turbine runs away from the highest efficiency point, there is a vortex flow at the exit of the runner, and a forced vortex center is generated at the center of the upper part of the draft tube. Due to the low internal pressure in the center of the vortex flow, the center of the forced vortex causes cavitation at σ hours and cavities in the central area. Especially at partial load operation, the center of forced vortex developed greatly. The cavitation cavities in the central area swirled eccentrically periodically in the draft tube to form surge phenomenon. But about forced vortex centers and swells