中文摘要：

抽水蓄能电站工况转换频繁,过渡过程中水泵水轮机可历经全特性4个象限,不稳定的复杂流动演变使过渡过程中事故频发。本文针对某低比转速模型水泵水轮机进行四象限全流道数值计算,得到同一开度下水轮机内部流态的演变规律。结果显示,在水泵区部分负荷工况,导叶区产生旋转失速现象,失速区的个数随流量大小变化;失速涡阻塞流道,使局部压力升高,产生周向传播的低频压力波动。在水泵制动区,当转速较高时,离心力作用使得水流不能均匀进入转轮,在转轮内产生旋转失速现象。在水轮机反“S”区,转轮进口产生的回流漩涡结构随流量在某些工况点的突变,导致沿转轮进口展向的流速分布呈现随流量而突变的现象。入流分布在飞逸点附近的突变使水流对转轮的做功特性发生突然变化,可能是导致空载不稳定的原因。

英文摘要：

The pump turbines have to change frequently between pumping and the requirements of the power grids. The path can track through four quadrants in the transient processes during which the unstable flow behavior can lead to generating modes to meet of the characteristics curves vibration of the units. CFD simulations on a pump-turbine model in four quadrants were carried out to reveal the onset and developed mechanisms of these unstable flow phenomena. The results show that the simulated characteristics curves are in good agreement with experiment results. At part load in pump mode, the rotating stall occurs within the guide vanes and the number of the stall cells can change with flow rate. The stall cells block the flow passages with a total pressure raise which resulting non-uniform pressure distributions rotating along the cir- cumference. In pump brake operation zone, when the impeller rotates at a high speed, the rotating stall may form within the impeller. In the turbine S-shaped operation zone, under different flow rate the flow re- circulation and vortex structures at the leading edge are different and change suddenly at some operating points, so the area average net flow rate at different height is different. At the runaway point, a sudden change of the distribution characteristics of the velocity along the height direction makes the characteristics of the water working on the runner changed, which may lead to the instability at no load.