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Journal of Hydrodynamics

, Volume 30, Issue 1, pp 131–139 | Cite as

Influence of upstream disturbance on the draft-tube flow of Francis turbine under part-load conditions

  • Ting Chen (陈婷)
  • Xianghao Zheng (郑祥豪)
  • Yu-ning Zhang (张宇宁)
  • Shengcai Li
Article

Abstract

Owing to the part-load operations for the enhancement of grid flexibility, the Francis turbine often suffers from severe low-frequency and large-amplitude hydraulic instability, which is mostly pertinent to the highly unsteady swirling vortex rope in the draft tube. The influence of disturbances in the upstream (e.g., large-scale vortex structures in the spiral casing) on the draft-tube vortex flow is not well understood yet. In the present paper, the influence of the upstream disturbances on the vortical flow in the draft tube is studied based on the vortex identification method and the analysis of several important parameters (e.g., the swirl number and the velocity profile). For a small guide vane opening (representing the part-load condition), the vortices triggered in the spiral casing propagate downstream and significantly affect the swirling vortex-rope precession in the draft tube, leading to the changes of the intensity and the processional frequency of the swirling vortex rope. When the guide vane opening approaches the optimum one (representing the full-load condition), the upstream disturbance becomes weaker and thus its influences on the downstream flow are very limited.

Keywords

Francis turbine vortex identification method instability vortex rope part-load condition swirl number 

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Notes

Acknowledgements

This work was suppored by the Fundamental Research Funds for the Central Universities (Grant No. JB2015RCY04), the Open Research Fund Program of Key Laboratory of Fluid and Power Machinery, Ministry of Education, Xihua University (Grant No. szjj-2017-100-1-003), the Open Foundation of National Research Center of Pumps, Jiangsu University (Grant No. NRCP201601) and the Open Research Fund Program of State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University (Grant No. LAPS16014).

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Copyright information

© China Ship Scientific Research Center 2018

Authors and Affiliations

  • Ting Chen (陈婷)
    • 1
    • 2
    • 3
  • Xianghao Zheng (郑祥豪)
    • 1
  • Yu-ning Zhang (张宇宁)
    • 1
    • 4
    • 5
  • Shengcai Li
    • 3
  1. 1.Key Laboratory of Condition Monitoring and Control for Power Plant Equipment, Ministry of Education, School of Energy, Power and Mechanical EngineeringNorth China Electric Power UniversityBeijingChina
  2. 2.School of ScienceWuhan Institute of TechnologyWuhanChina
  3. 3.School of EngineeringUniversity of WarwickCoventryUK
  4. 4.Key Laboratory of Fluid and Power Machinery, Ministry of EducationXihua UniversitySichuanChina
  5. 5.National Research Center of PumpsJiangsu UniversityZhenjiangChina

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