Investigation of the vortex evolution and hydraulic excitation in a pump-turbine operating at different conditions

• Published in: Renewable energy 2021-06, Vol.171, p.462-478
• Main Authors: Yu, An, Wang, Yongshuai, Tang, Qinghong, Lv, Ruirui, Yang, Zhongpo
• Format: Article
• Language: English
• Subjects: Draft tube; Pressure fluctuations; Pump-turbine; Vortex evolution
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2021.02.131

When the pump-turbine operates at off-design conditions, vortex rope usually occurs in the draft tube and causes low-frequency pressure fluctuations. In this paper, the evolution of the vortex rope and its association with the low-frequency pressure fluctuations under typical operating conditions are investigated. The results indicate that: 1) The frequency of pressure fluctuation is mainly affected by the vortex’s rotation frequency in the draft tube without cavitation. While when cavitation occurs, the frequency of pressure fluctuations in the draft tube is primarily affected by the cavitation volume evolution; 2) Under the non-cavitation condition, the overall vortex rope behaves as a spiral vortex rope under part-load condition, a slender column under design condition, and pear-shaped vortex rope under full-load condition. The vortex rope directly disappears when cavitation occurs under part-load condition. In contrast, the vortex rope becomes unstable, and changes from a single-phase vortex rope to a multi-phase vortex rope under the design condition. While at the full-load condition, the vortex rope becomes slenderer, and the rotation is more noticeable than under the non-cavitation condition. •A new multiphase flow simulation method is proposed and proved in pump-turbine.•The correlation mechanism between vortex and pressure fluctuations is revealed.•The spatial distribution law of low-frequency pressure fluctuations is studied.