Hidden hydraulic instability: Clearance flow dynamics during pump-turbine pump mode startup

Ming Xia, Zhengwei Wang, Wei Wang, Jing Yang, Weiqiang Zhao and Mu Qiao

Renewable Energy, 2025, vol. 252, issue C

Abstract: As renewable energy integration increases, pumped storage hydropower stations face growing stability challenges due to frequent starting and stopping operations. This study focuses on hydraulic instability during pump-turbine startup in pump mode, with particular emphasis on the role of clearance flow during the critical guide vane opening process. Through field tests on a 150 MW pump-turbine, two distinct vibration peaks were identified during guide vane opening, and the evolution of pressure fluctuations was successfully reproduced using full-passage CFD simulations. Further flow field analysis revealed that guide vane end clearance flow induces the Coanda effect and interacts with the main flow, forming complex leakage vortex structures that particularly impact axial hydraulic thrust and guide vane hydraulic moments during the early and intermediate stages. The findings reveal that clearance flow can significantly amplify flow instabilities during pump-turbine transient processes at special moment, even though the clearance gaps are only submillimeter-scale. This comprehensive understanding of clearance flow dynamics provides new insights into flow instability during transient processes and theoretical support for improving design level and optimizing startup strategies.

Keywords: Pump-turbine; Transient process; Clearance flow; Hydraulic stability; Vortex evolution (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:252:y:2025:i:c:s0960148125009747

DOI: 10.1016/j.renene.2025.123312

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