水泵水轮机泵工况压力脉动和转轮受力特性

为研究水泵水轮机在泵工况下的内部流态变化对压力脉动和转轮叶片受力的影响，采用 SAS－SST 湍流模型对某一模型水泵水轮机的多个非设计工况进行非定常数值模拟，分析了水轮机 内部流态对导叶与转轮之间无叶区、尾水管内的压力脉动和转轮叶片径向受力的影响。结果表明: 在流量为 40% ～80%设计流量时，导叶区内产生旋转失速，转失速涡团初生于固定导叶进口，并随着流量的降低向活动导叶进口发展，且覆盖区域逐渐增大。旋转失速使压力和过流沿周向不均匀分布， 导致压力脉动和转轮径向受力波动大幅上升。在40%设计流量时，失速涡团发展最为充分，无叶区 压力脉动和转轮受力波动的低频分量幅值最高。旋转失速产生的低频脉动可向尾水管传播，形成的低 频压力脉动幅值约为无叶区低频脉动幅值的10%。当流量低于 40%设计流量时，导叶区旋转失速消失，复杂的涡结构形成的压力脉动低频成分没有周期性。此外，转轮进口的流动分离使尾水管内产生复杂的回流涡结构，导致尾水管内形成频谱丰富的压力脉动; 流量降低使转轮进口回流涡结构的湍动 能增加，导致尾水管内压力脉动幅值大幅上升。小流量工况下，转轮进口的涡结构演变是转轮径向力波动的主要影响因素。

Pressure pulsation and runner mechanical property during pumping mode of pump-turbine

In order to study the influence of the internal flow pattern change of pump-turbine on the pressure pulsation and mechanical property of runner blade under the condition of pumping mode，the unsteady numerical simulations on several off-design operation conditions of a model pump-turbine are made with SAS-SST turbulence model，and then the influences from the internal flow pattern on the vaneless space between guide vane and runner，the pressure pulsation inside the draft tube and the radial stress of the runner blade are analyzed. The results show that when the pump-turbine operates at the flow rate of 40% ～ 80% of the designed one，the rotating stall occurs inside the guide vane region，of which the rotating stall vortex initially creates at the stay vane inlet and develops toward the movable guide vane inlet，and then the covering area is gradually enlarged. The rotating stall makes pressure and passing-flow unevenly distribute along the circumferential direction and leads the pressure pulsation and the fluctuation of the radial stress of runner to be largely increased. Under the operation condition of the design flow rate of 40%，the development of the rotating stall vortex is most sufficient with the highest amplitudes of low frequency components of both the pressure pulsation in the vaneless space and the fluctuation of runner stress. The low frequency pulsation created by the rotating stall can propagate toward the draft tube，of which the amplitude of the created low frequency pressure pulsation is about 10% of that in the vaneless space. When the flow rate is lower than the design flow rate by10%，the rotating stall in the vaneless space is to disappear without the periodicities of the low-frequency components of the pressure pulsation created by the complicated vortex structure. Additionally，the flow separation at the runner inlet makes a complicated backflow vortex occur in the draft tube and then leads a pressure pulsation with rich frequency spectra to be created inside the draft tube，while the decrease of the flow rate makes the turbulence kinetic energy of the backflow vortex structure at the runner inlet increase and then leads the amplitude of the pressure pulsation in the draft tube to be largely increased. Under the condition of small flow rate，the evolution of the vortex structure at the runner inlet is the main factor affecting the fluctuation of the runner radial force.