Flow characteristics of a Francis turbine under deep part-load and various no-load conditions

IF 2.3 3区 工程技术 Q2 ENGINEERING, MECHANICAL Experiments in Fluids Pub Date : 2024-11-04 DOI:10.1007/s00348-024-03904-y
Araz Rezavand Hesari, Maxime Gauthier, Maxime Coulaud, Yvan Maciel, Sébastien Houde
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Abstract

In the recent years, increased use of hydraulic turbines in off-design operating conditions such as no-load and deep part-load has resulted in increased damage to the turbines. A detailed understanding of the fluctuating flow phenomena can help to identify and mitigate the potentially damaging flow structures. This paper presents a comprehensive experimental and numerical study of the flow phenomena at the inlet of a Francis turbine at four no-load operating conditions, including speed-no-load and a deep part-load operating condition. Measurements are taken using a high-frequency stereoscopic endoscopic particle image velocimetry method on radial–azimuthal planes, covering the vaneless space and a large part of the interblade channels at different spans. For the speed-no-load condition, experimental data are enriched with unsteady RANS simulation data to understand the three-dimensional behavior of the flow. The average flow phenomena, transient structures and velocity fluctuations are discussed and compared among different operating points. At all operating points, the strongest average flow circulation zone (strong enough to form a vortex only at one operating condition) consistently exhibits the highest velocity fluctuation energy. The results show that the highest velocity fluctuations, and thus the most energetic dynamic structures, are in a no-load operating point with a guide vane opening smaller than speed-no-load. Position and intensity of the interblade vortices varies not only with the guide vane opening but also with the amount of torque extracted by the runner.

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混流式水轮机在深度部分负荷和各种空载条件下的流量特性
近年来,水轮机在空载和深度部分负载等非设计运行条件下的使用增加,导致水轮机损坏率上升。详细了解波动流动现象有助于识别和减轻潜在的破坏性流动结构。本文对混流式水轮机在四种空载运行条件下的进水口流动现象进行了全面的实验和数值研究,包括无速度无负荷和深部分负荷运行条件。测量采用高频立体内窥镜粒子图像测速法,在径向-方位角平面上进行,覆盖了不同跨度的无叶空间和大部分叶间通道。在无速度无载荷条件下,实验数据与非稳态 RANS 模拟数据相结合,以了解流动的三维行为。讨论并比较了不同工作点的平均流动现象、瞬态结构和速度波动。在所有运行点上,最强的平均流环流区(仅在一种运行条件下足以形成涡旋)始终表现出最高的速度波动能量。结果表明,在导叶开度小于无速度-无负荷的无负荷运行点,速度波动最大,因此动态结构的能量也最大。叶片间涡流的位置和强度不仅随导叶开度的变化而变化,还随转轮提取的扭矩大小而变化。
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来源期刊
Experiments in Fluids
Experiments in Fluids 工程技术-工程:机械
CiteScore
5.10
自引率
12.50%
发文量
157
审稿时长
3.8 months
期刊介绍: Experiments in Fluids examines the advancement, extension, and improvement of new techniques of flow measurement. The journal also publishes contributions that employ existing experimental techniques to gain an understanding of the underlying flow physics in the areas of turbulence, aerodynamics, hydrodynamics, convective heat transfer, combustion, turbomachinery, multi-phase flows, and chemical, biological and geological flows. In addition, readers will find papers that report on investigations combining experimental and analytical/numerical approaches.
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