水泵水轮机水轮机工况全流道三维非定常数值模拟

Numerical simulation of unsteady three-dimensional flow in turbine mode of a pump-turbine

为了研究水泵水轮机水轮机工况下的内部流场及压力脉动特性,对某蓄能电站的水泵水轮机几何建模,采用RNG k-ε模型和SIMPLE算法,对水泵水轮机水轮机工况时三维全流道的空载工况、25%负荷工况、50%负荷工况、75%负荷工况、额定工况及满负荷工况进行三维非定常模拟;同时,监测蜗壳入口、活动导叶之间、导叶与转轮之间无叶区,以及尾水管直锥段和弯肘段的压力脉动情况.结果表明:空载等低负荷工况下,活动导叶出口出现射流,使导叶与转轮间无叶区流场恶化及转轮叶片进水边附近产生涡结构,随负荷增加而缓解;50%负荷工况下,尾水涡带有多分支相互缠绕,导叶与转轮间无叶区受动静干涉高频脉动的影响,尾水管区域受尾水涡带低频脉动影响,且各自向上、下游传播;额定工况下,P1至P5测点压力脉动的压力呈现阶梯依次降低,转轮前、后部分转轮与导叶间无叶区测点P3、尾水管锥段测点P4的脉动压力值出现很大的落差;各工况下导叶与转轮间无叶区脉动频率不变,各频率幅值随负荷增加而增大.

In order to study the fluid flow and pressure fluctuation characteristics in the turbine mode of a pump - turbine, the geometrical model of a pump - turbine in a pumped storage power station is generated, and unsteady three-dimensional flows in the turbine mode are simulated by employing the RNG k-ε model and SIMPLE algorithm under 25%, 50%, 75% and 100% （full） load conditions, respectively. At the same time, the pressure pulsations at the inlet of volute, in the range of wicket gate, in the vaneless range between the wicket gate and the runner, in the conical diffuser and elbow of the draft tube are monitored. The results show that jet flows are issued at the wicket gate outlet un- der no-load and 25% load conditions, causing a deteriorated flow field in the vaneless range and a vor- tex structure near the runner inlet, fortunately this situation is relieved with increasing load. Under 50% load condition, there are a few vortex rope branches to intertwine each other, the vaneless range affected hy the rotor - stator interaction of high frequency, and the flow in the draft tube is influ- enced by vortex ropes of low frequency, further, the interaction and rope low frequency pulsation pro- pagate upstream and downstream, respectively. Under 75% and lull load conditions, the pressure flu- ctuation amplitude decreases from monitoring points P1 to P5, particularly, the amplitude at point P3 in the vaneless range and point P4 in the conical diffuser declines sharply. The pulsation frequency in the vaneless range remains unchanged when the load changes, and the amplitude of various frequencies ri- ses with increasing load.