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Energy Balance and Local Unsteady Loss Analysis of Flows in a Low Specific Speed Model Pump-Turbine in the Positive Slope Region on the Pump Performance Curve

Author

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  • Guocheng Lu

    (State Key Laboratory of Hydro Science and Engineering, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China)

  • Zhigang Zuo

    (State Key Laboratory of Hydro Science and Engineering, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China)

  • Demin Liu

    (Research & Test Center, Dongfang Electric Machinery Co. Ltd, Deyang 618000, China)

  • Shuhong Liu

    (State Key Laboratory of Hydro Science and Engineering, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China)

Abstract

The positive slope on the pump performance curve of pump-turbines suggests potential operational instabilities in pump mode. Previous research has indicated that the increase of the hydraulic loss caused by sudden changes of flow patterns in pump-turbines is responsible for the positive slope, however its detailed flow mechanism is still unclear. A low specific speed model pump-turbine was numerically investigated against experiments in the present study, by applying unsteady RANS (Reynolds-Averaged Navier–Stokes equations) simulations with a v 2 - f turbulence model. The mechanism of occurrence of the positive slope on the pump performance curve was discussed regarding the energy balance, as this region appears when the value of ∂ P u ∂ Q is larger than the critical value P u Q . An unsteady local loss analysis, derived from the energy equation, was conducted to illustrate the contribution of local flow patterns to the loss in corresponding hydraulic components. The variation of the kinetic energy of the mean flow was taken into account for the first time so that this method can be applied to highly time dependent flow patterns, e.g., a rotating stall in the present study. The investigations on the flow patterns revealed that some guide vane channels stalled with a larger discharge coefficient than the positive slope region. Several guide vane channels near the stalled channels were stalling with minor decrease of the discharge coefficient, leading to sudden increases of the input power and the loss. When the discharge coefficient slightly decreased in further, the pump-turbine operated into the positive slope region, and the rotating stall with 3 stall cells appeared, proven by the FFT (Fast Fourier Transform) and cross-phase analysis on the pressure fluctuations.

Suggested Citation

  • Guocheng Lu & Zhigang Zuo & Demin Liu & Shuhong Liu, 2019. "Energy Balance and Local Unsteady Loss Analysis of Flows in a Low Specific Speed Model Pump-Turbine in the Positive Slope Region on the Pump Performance Curve," Energies, MDPI, vol. 12(10), pages 1-22, May.
    • Handle: RePEc:gam:jeners:v:12:y:2019:i:10:p:1829-:d:231065
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    References listed on IDEAS

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    1. Zuo, Zhigang & Liu, Shuhong & Sun, Yuekun & Wu, Yulin, 2015. "Pressure fluctuations in the vaneless space of High-head pump-turbines—A review," Renewable and Sustainable Energy Reviews, Elsevier, vol. 41(C), pages 965-974.
    2. Lu, Guocheng & Zuo, Zhigang & Sun, Yuekun & Liu, Demin & Tsujimoto, Yoshinobu & Liu, Shuhong, 2017. "Experimental evidence of cavitation influences on the positive slope on the pump performance curve of a low specific speed model pump-turbine," Renewable Energy, Elsevier, vol. 113(C), pages 1539-1550.
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    Cited by:

    1. Li, Wei & Li, Enda & Ji, Leilei & Zhou, Ling & Shi, Weidong & Zhu, Yong, 2020. "Mechanism and propagation characteristics of rotating stall in a mixed-flow pump," Renewable Energy, Elsevier, vol. 153(C), pages 74-92.
    2. Yong Liu & Dezhong Wang & Hongjuan Ran & Rui Xu & Yu Song & Bo Gong, 2021. "RANS CFD Analysis of Hump Formation Mechanism in Double-Suction Centrifugal Pump under Part Load Condition," Energies, MDPI, vol. 14(20), pages 1-17, October.
    3. Sun, Longyue & Pan, Qiang & Zhang, Desheng & Zhao, Ruijie & Esch, B.P.M.(Bart) van, 2022. "Numerical study of the energy loss in the bulb tubular pump system focusing on the off-design conditions based on combined energy analysis methods," Energy, Elsevier, vol. 258(C).
    4. Luo, Xianwu & Ye, Weixiang & Huang, Renfang & Wang, Yiwei & Du, Tezhuan & Huang, Chenguang, 2020. "Numerical investigations of the energy performance and pressure fluctuations for a waterjet pump in a non-uniform inflow," Renewable Energy, Elsevier, vol. 153(C), pages 1042-1052.
    5. Ye, Weixiang & Ikuta, Akihiro & Chen, Yining & Miyagawa, Kazuyoshi & Luo, Xianwu, 2020. "Numerical simulation on role of the rotating stall on the hump characteristic in a mixed flow pump using modified partially averaged Navier-Stokes model," Renewable Energy, Elsevier, vol. 166(C), pages 91-107.

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