抽水蓄能电站输水系统水力振荡可能性分析

抽水蓄能电站输水系统布置复杂，机组工况多且转换频繁，因水泵水轮机不稳定流动导致输水系统振荡甚至产生共振的可能性较大。本研究旨在分析水泵水轮机各种不稳定因素与输水系统发生共振的可能性。首先总结了水泵水轮机尾水管涡、旋转失速等不稳定流动的发生工况和频率范围；其次以某抽水蓄能电站为例，采用传递矩阵法计算输水系统自振频率特性，发现尾水管涡和旋转失速频率与系统频率重叠，有引起共振可能性；进一步以尾水管涡扰动作为振源对输水系统进行强迫振荡分析，得出系统沿线的压力振荡幅值分布。研究表明，尾水涡带和旋转失速最可能导致系统水力共振，某些电站出力波动可能与此有关；S区振荡也可能引起强烈的水力振荡，造成机组过渡过程事故；动静干涉、卡门涡是高频振动，主要影响水轮机压力脉动，可导致转轮结构共振和破坏，与输水系统共振的可能性小。

Discussion on hydraulic oscillations of water transfer systems in pumped-storage power stations

In a pumped-storage power station, complex layout of its water transfer system and frequent change in its working condition often cause hydraulic oscillations or even hydraulic resonances. This paper summarizes unstable characteristics of the flows in pump-turbines and clarifies their relationship with the hydraulic oscillations of the transfer system. First, we examine the pump-turbine working conditions for the occurrence of unsteady flows and their typical frequency ranges related to draft tube vortices, rotating stalls, unstable oscillations in the S region, rotor stator interaction, vane tip Karman vortices, etc. Then, natural frequencies of a typical water transfer system are calculated using the transfer matrix method and compared with the frequencies of unstable flows in the pump-turbine. We found out that the frequencies of draft tube vortices and rotating stalls overlap with those of the hydraulic system, indicating the possibility to cause hydraulic resonances. Finally, the forced oscillations of the transfer system are simulated with given head disturbances to draft tube flows. The results show that draft tube vortices and rotating stalls are more likely to cause hydraulic resonances, which could lead to fluctuations in the power output. Also, oscillations in the S region could induce hydraulic oscillations during transient process. On the other hand, the high frequency characteristics of rotor-stator interactions and Karman vortices could originate the structural resonances of runners but not the hydraulic resonances in water transfer systems, for they mainly affect high-frequency pressure pulsations.