水泵水轮机飞逸工况下尾水管涡带演化研究

A study on the evolution of vortex in the draft tube of pump-turbine under the runaway condition

为研究水泵水轮机在飞逸工况下不同导叶开度时的水力不稳定性,以某抽水蓄能电站水泵水轮机为研究对象,基于Realizable k-ε湍流模型的非定常数值计算方法,对水泵水轮机七种不同导叶开度下的流动进行全流道计算。结合监测蜗壳进口、无叶区、转轮与顶盖之间以及尾水管处的压力脉动,研究了水泵水轮机在不同导叶开度下尾水管涡带的形态,及其对尾水管压力脉动的影响。结果表明:飞逸工况下,尾水管涡带与开导叶度关系密切;小开度下,涡带较明显且涡带形态不断撕裂重构并伴有局部回流;随开度增大,尾水管涡带的形态逐渐由紊乱无规则变为明显锥状,且随着开度的进一步增大涡带形状演变为粗壮螺旋涡带。大开度下,涡带近壁面旋向侧速度较大是导致直锥段壁面湍动能较大等能量损失的主要原因;尾水管涡带不断向下游输运,是造成水泵水轮机尾水管巨大压力脉动的关键因素。

To study the hydraulic instability of pump-turbine under runaway condition with different guide vane openings,the pump-turbine of a certain pumped storage power station was employed.Based on the Realizable k-εturbulent model,the unsteady flow of the whole passage of the pump-turbine with seven different guide vane openings was calculated.The pressure fluctuation of the inlet of the volute,blade free section,the region between the runner and the roof,and draft tube was monitored to study the evolution of vortex shape and pressure fluctuation on the draft tube with the effects on different guide vane opening.Results show that when the guide vane opening is different under runaway condition,there is a distinct difference of the shape of the vortex.In the small guide vane opening,the vortex is obvious and the shape of the vortex changes constantly.With the increase of the guide vane opening,the shape of the vortex tends to the pattern of geometric cone from the disordered status,as well as the screw vortex rope presents the thicker tendency gradually.In the large guide vane opening,the higher velocity distribution near the vortex rope wall leads to the great loss of turbulent kinetic energy and other forms of energy near the straight cone region.Meanwhile,the key reason why great pressure fluctuation is caused in the draft tube is that the vortex is transported continuously towards the downstream.