Influence of Clearance Flow on Dynamic Hydraulic Forces of Pump-Turbine during Runaway Transient Process

Xiaoxia Hou, Yongguang Cheng, Zhiyan Yang, Ke Liu, Xiaoxi Zhang and Demin Liu
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Xiaoxia Hou: State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
Yongguang Cheng: State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
Zhiyan Yang: State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
Ke Liu: State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
Xiaoxi Zhang: School of Environmental Science and Engineering, Xiamen University of Technology, Xiamen 361024, China
Demin Liu: Dongfang Electric Machinery Co., Ltd., Deyang 618000, China

Energies, 2021, vol. 14, issue 10, 1-20

Abstract: The clearance flow around the pump-turbine runner has significant influences on unit vibrations, which may cause accidents in transient processes. The dynamic hydraulic forces and flow patterns in the clearance flow channel (CFC) of a low specific-speed pump-turbine were analyzed based on 3D CFD simulations during the runaway oscillating process. It is shown that the axial force of the runner periodically fluctuates with large amplitudes, and its components in CFC and the main flow channel (MFC) demonstrate a similar significance level. The CFC component was formulated as a function of the clearance inlet pressure and rotational speed, while the MFC component as a function of the momentum changing rate and the runner outlet pressure force. The fluctuation of runner radial force is mainly caused by the flow evolution in MFC, however, the flow in CFC aggravates it. The pressure in CFC shows a few pulsating signals from MFC, and the radial pressure drop in CFC is proportional to the square of both radius and rotational speed. In CFC, strong rotating shear flow containing a velocity core region in the circumferential direction is formed, and rotational speed is the dominant factor.

Keywords: pump-turbine; runaway transient process; runner forces; clearance leakage; clearance flow patterns (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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