Flow Evolution and Energy Loss Mechanism in Accidental Shutdown Process of a Large Submersible Mixed-Flow Pump System

Document Type : Regular Article

Authors

1 School of Energy and Power Engineerning, University of Shanghai for Science and Technology, Shanghai 200093, China

2 Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering, Shanghai 200093, China

3 Yangtze River Survey Planning and Design Research Co., LTD, Shanghai Branch, Shanghai 200439, China

Abstract

To investigate the accidental shutdown process for a large vertical and submersible mixed-flow pump unit in a drainage pumping station, a three-dimensional numerical method for this transition process was proposed according to the angular momentum balance theorem and rigid body rotation technology. We obtained the transient performance curves of the unit and the internal flow characteristics of the full flow channel. In addition, we also analyzed the energy loss distribution of the through-flow components during this progress based on the entropy production theory. The results show that the whole runaway process needs to go through four stages: the pump mode, the pump braking mode, the turbine mode, and the stable runaway mode. The pressure amplitude changes greatly in impeller and guide vanes, and the main fluctuation frequency is the blade frequency. There are higher harmonic frequencies in the dynamic rotor-stator interface. As the rotating speed increases in turbine mode, the negative pressure area near the impeller blade’s trailing edge gradually increases. The entropy production method can be used to determine the location, intensity of energy loss during the transient process. If the rotating speed exceeds the allowed value in the runaway turbine mode, the interaction between blade tip vortex and hub vortex rope may cause loss of stability.

Keywords

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History

  • Received: 22 September 2022
  • Revised: 28 November 2022
  • Accepted: 02 January 2023
  • Available online: 01 May 2023

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