A Study on the Transient Flow Characteristics of Pump Turbines Across the Full Operating Range in Turbine Mode

Hongqiang Tang, Qifei Li (), Xiangyu Chen, Zhanyong Li and Shiwei Li ()
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Hongqiang Tang: School of Intelligent Equipment, Lanzhou College of Information Science and Technology, Lanzhou 730300, China
Qifei Li: School of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou 730050, China
Xiangyu Chen: School of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou 730050, China
Zhanyong Li: Tianjin Tianfa Heavy Machinery and Hydro Power Equipment Manufacture Co., Ltd., Tianjin 300400, China
Shiwei Li: School of Intelligent Equipment, Lanzhou College of Information Science and Technology, Lanzhou 730300, China

Energies, 2025, vol. 18, issue 13, 1-28

Abstract: The transient operation of pump turbines generates significant flow-induced instabilities, prompting a comprehensive numerical investigation using the SST k − ω turbulence model to examine these instability effects throughout the complete operating range in turbine mode. This study specifically analyzes the evolutionary mechanisms of unsteady flow dynamics under ten characteristic off-design conditions while simultaneously characterizing the pressure fluctuation behavior within the vaneless space (VS). The results demonstrate that under both low-speed conditions and near-zero-discharge conditions, the VS and its adjacent flow domains exhibit pronounced flow instabilities with highly turbulent flow structures, while the pressure fluctuation amplitudes remain relatively small due to insufficient rotational speed or flow rate. Across the entire turbine operating range, the blade passing frequency (BPF) dominates the VS pressure fluctuation spectrum. Significant variations are observed in both low-frequency components (LFCs) and high-frequency, low-amplitude components (HF-LACs) with changing operating conditions. The HF-LACs exhibit relatively stable amplitudes but demonstrate significant variation in the frequency spectrum distribution across different operating conditions, with notably broader frequency dispersion under runaway conditions and adjacent operating points. The LFCs demonstrate significantly higher spectral density and amplitude magnitudes under high-speed, low-discharge operating conditions while exhibiting markedly reduced occurrence and diminished amplitudes in the low-speed, high-flow regime. This systematic investigation provides fundamental insights into the flow physics governing pump-turbine performance under off-design conditions while offering practical implications for optimizing transient operational control methodologies in hydroelectric energy storage systems.

Keywords: pump turbine; off-design operating conditions; turbine mode; transient flow; pressure pulsation (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: 2025
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