Investigation on transient flow and energy dissipation during run away process in Francis turbine

被引：0
|
作者：
Li Y. [1 ]
Sun L. [1 ]
Guo P. [1 ,2 ]
Fan W. [1 ]
Xu Z. [1 ]
机构：
[1] School of Water Resources and Hydroelectric Engineering, Xi'an University of Technology, Xi'an
[2] State Key Laboratory of Eco—hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an
来源：
Shuili Xuebao/Journal of Hydraulic Engineering | 2023年 / 54卷 / 07期
关键词：
energy dissipation; Francis turbine; runaway process; transient flow; vortex;
D O I：
10.13243/j.cnki.slxb.20230079
中图分类号：
学科分类号：
摘要：
Transient hydraulic characteristics such as flow separation, vortex structure, and high —amplitude pressure pulsation will appear inside the turbine and undergo the runaway transition process. In order to clarify the hydraulic characteristics of the turbine during the runaway process, a low-head Francis model turbine is used as the research subject in this paper. The transient flow process from rated speed to runaway speed is numerically studied, and the runaway speed and discharge are determined. These results are in good agreement with the findings from the experiments. The study' s findings demonstrate that a large incidence angle causes a strong flow separation phenomenon near the runner inlet, which creates a massive vortex structure in the runner blade passage. With the increase of the rotating speed, the volume of the vortex structure increases gradually, and the vortex structure disturbs the main flow strongly. The low-frequency and high-amplitude pressure fluctuations with broadband characteristics are captured by numerical calculation, and its frequency range is below 0.5 times the blade passing frequency. Besides, the corresponding pressure amplitude of the runner region is the highest. The energy dissipation characteristics of the turbine are further analyzed on the basis of energy balance equation, and it is found that the energy dissipation of each flow passage component mainly occurs in the initial stage of the rise of the speed, and the sum of the energy dissipation in the runner and the draft tube exceeds 90% of the total energy dissipation. Additionally, turbulence dominates energy transport and dissipation in the unstable runaway process, as shown by the fact that the turbulent kinetic energy generation term and the Reynolds stress work term are much larger than the viscous dissipation term and the viscous force work term. Besides, the location of the main energy dissipation in the wheel coincides with the location of the vortex during rotation, suggesting that the intricate vortex structure in the wheel is the source of energy dissipation. It points out the direction for further study on the energy dissipation mechanism of the turbine transient runaway process. © 2023 China Water Power Press. All rights reserved.
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页码：794 / 805
页数：11
相关论文
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