水泵水轮机在水轮机工况下压力脉动特性

为了研究水泵水轮机在水轮机工况下的压力脉动特性,采用SST k-ω湍流模型对模型水泵水轮机在水轮机工况下的三维非定常湍流进行模拟.在试验验证的基础上,通过调整活动导叶的开度以实现机组不同的运行工况,分析了3种流量工况下导叶、转轮和尾水管内的压力脉动规律.结果表明,尾水涡带形态和旋转方向对机组压力脉动的影响很大:在小流量工况下,尾水涡带为螺旋状,旋转方向与转轮转动方向相同,转轮出口产生强烈的低频压力脉动,转轮叶片上的压力脉动频率约为转轮转频的0.62倍,尾水管压力脉动主频约为转轮转频的0.36倍;在最优工况和大流量工况下,尾水涡带变为管状,转轮出口压力脉动幅值变小,在转轮叶片表面检测到与尾水管压力脉动主频相同的压力脉动;大流量工况下涡带旋转方向与转轮旋转方向相反,尾水管内压力脉动的最大值出现在弯肘段区域.

Characteristics of pressure fluctuation in pump-turbine in turbine mode

In order to investigate the pressure fluctuation characteristics of pump-turbine in turbine mode, a three-dimensional unsteady flow in a pump-turbine is numerically simulated using the shear stress transport(SST)k-ω turbulence model. By comparing computational flow discharge and efficiency with experimental ones, the flow models are validated. The pressure fluctuations in the guide vanes, runner and draft tube under three different operational conditions are analyzed, respectively. The results show that both the shape and the rotating direction of vortex rope have an obvious influence on the pressure fluctuation. At a low discharge, vortex rope is helical and has the same rotating direction with the runner, a severe low-frequency pressure fluctuation appears at the runner outlet. The frequency of pressure fluctuation on the runner blade is about 0.62 times the runner rotational frequency and the dominant frequency in the draft tube is about 0.36 times the runner rotational frequency. At an optimum and large discharge, the vortex rope is tubular, the amplitude of pressure fluctuation at the runner outlet is reduced. The dominant frequency of the pressure fluctuation in the draft tube is the same as the frequency of pressure fluctuation on the runner blade. At a large discharge, the vortex rope is in the inverse rotating direction of the runner, and the maximal amplitude in the pressure fluctuation in the draft tube appears at the tube elbow. 