不同开度下水泵水轮机叶道内流畸变对转轮的受力影响研究

Impact of Blade Passage Flow Distortions on Runner Forces in Pump-turbine under Different Guide Vane Openings

摘要:

水泵水轮机导叶开度的变化会引起转轮内部的内流畸变，为了研究这种内流畸变对转轮受力的影响，以国内某抽水蓄能电站的模型机为研究对象，在试验研究的基础上采用SST k-ω湍流模型对不同开度下的水泵水轮机全流道进行三维非定常数值模拟计算，研究不同导叶开度下引起的叶道内流畸变对转轮叶片和转轮径向力的影响。结果表明：随着导叶开度的增大，叶道内部流速也随之变大，流道内最大速度分布于叶片工作面附近，且每个流道均有漩涡存在，其涡核位置位于叶片相对位置的2/3处；转轮叶片受力受到叶道内部流动畸变产生的涡流影响，叶片工作面最小压力发生的位置和叶片背面最大压力发生的位置均在涡核附近；叶道内部流动畸变产生的不稳定流动对转轮的径向力造成规律性影响，使得转轮所受径向力合力的峰谷个数与叶道数相同，与叶道内部流动畸变引起的内部涡流变化一致。

Abstract:

The variation of guide vane opening in pump-turbines induces internal flow distortions within the runner, significantly influencing hydraulic performance and structural integrity. To investigate the impact of such flow distortions on runner dynamics, a combined experimental and numerical approach was employed, focusing on a model pump-turbine from a domestic pumped-storage power station. Utilizing the SST k-ω turbulence model, three-dimensional unsteady numerical simulations were conducted across the full flow passage under different guide vane openings. Aiming to elucidate the relationship between guide vane-induced flow distortions and the resultant hydrodynamic forces on the runner blades and radial loads.The findings revealed that as the guide vane opening increased, the internal flow velocity within the runner passage was escalated, with the maximum velocity localized near the pressure side of the blades. Notably, each blade passage exhibited a distinct vortex structure, with the vortex core positioned at approximately two-thirds of the blade’s relative length. These vortices, arising from flow separation and secondary flows, critically influenced the pressure distribution on the runner blades. Specifically, the minimum pressure on the PS and the maximum pressure on the suction side consistently occurred near the vortex core, highlighting the role of flow distortions in dictating blade loading patterns. Furthermore, the unsteady flow distortions exerted a systematic impact on the radial forces acting on the runner. The resultant radial force exhibited periodic fluctuations, with the number of peaks and troughs corresponding to the number of runner blades. This periodicity aligned with the spatial distribution and temporal evolution of the vortices within the blade passages, underscoring the coherence between flow instabilities and mechanical excitations. The study demonstrated that the runner’s radial force characteristics were intrinsically linked to the dynamic behavior of the vortical structures, which were modulated by the guide vane opening. These insights contributed to a deeper understanding of the fluid-structure interaction mechanisms in pump-turbines under off-design conditions. The results emphasized the necessity of optimizing guide vane control strategies to mitigate adverse flow distortions, thereby enhancing operational stability and fatigue resistance. The methodology and conclusions presented herein can provide a foundation for further investigations into transient hydraulic phenomena in reversible pump-turbines, with implications for design and condition monitoring in pumped-storage systems.