Study of the vortex-induced pressure excitation source in a Francis turbine draft tube by particle image velocimetry

A. Favrel*, A. Müller, C. Landry, K. Yamamoto, F. Avellan

*この研究の対応する著者

研究成果: Article査読

108 被引用数 (Scopus)

抄録

Francis turbines operating at part-load experience the development of a precessing cavitation vortex rope at the runner outlet, which acts as an excitation source for the hydraulic system. In case of resonance, the resulting pressure pulsations seriously compromise the stability of the machine and of the electrical grid to which it is connected. As such off-design conditions are increasingly required for the integration of unsteady renewable energy sources into the existing power system, an accurate assessment of the hydropower plant stability is crucial. However, the physical mechanisms driving this excitation source remain largely unclear. It is for instance essential to establish the link between the draft tube flow characteristics and the intensity of the excitation source. In this study, a two-component particle image velocimetry system is used to investigate the flow field at the runner outlet of a reduced-scale physical model of a Francis turbine. The discharge value is varied from 55 to 81 % of the value at the best efficiency point. A particular set-up is designed to guarantee a proper optical access across the complex geometry of the draft tube elbow. Based on phase-averaged velocity fields, the evolution of the vortex parameters with the discharge, such as the trajectory and the circulation, is determined for the first time. It is shown that the rise in the excitation source intensity is induced by an enlargement of the vortex trajectory and a simultaneous increase in the precession frequency, as well as the vortex circulation. Below a certain value of discharge, the structure of the vortex abruptly changes and loses its coherence, leading to a drastic reduction in the intensity of the induced excitation source.

本文言語English
論文番号215
ページ(範囲)1-15
ページ数15
ジャーナルExperiments in Fluids
56
12
DOI
出版ステータスPublished - 2015 12月 1
外部発表はい

ASJC Scopus subject areas

  • 計算力学
  • 材料力学
  • 物理学および天文学(全般)
  • 流体および伝熱

フィンガープリント

「Study of the vortex-induced pressure excitation source in a Francis turbine draft tube by particle image velocimetry」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。

引用スタイル