Investigation of Channel Vortices in Francis Turbines

Liu, M; Zhou, Lingjiu; Wang, Z W; Liu, D M; Zhao, Yongzhi

doi:10.1088/1755-1315/49/8/082003

Cited by 7 publications

(3 citation statements)

References 15 publications

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“…Liu et al [14] suggested that the larger incidence angle between the inflow angle and the blade angle on the leading edge of the runner was the formation factor of the channel vortex. Liu et al [15] believed that the channel vortex was caused by the reverse flow of water in the draft tube. Zhang et al [16] considered the unsteady vortex flow in the straight cone section as the main cause of the vortex rope in the draft tube.…”

Section: Introductionmentioning

confidence: 99%

Study on Flow Characteristics of Francis Turbine Based on Large-Eddy Simulation

Xu,

Cheng,

Lin

et al. 2023

Water

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The research object was a Francis turbine, and the working conditions at 100%, 75%, 50%, 25%, and 1% opening were determined by the opening size of the guide vane. Large-Eddy Simulation (LES) was adopted as a turbulence model method to conduct three-dimensional unsteady turbulent numerical simulation of the entire flow channel of a Francis turbine, and the flow situation of various parts of the turbine under different working conditions was obtained. The flow characteristics of each component under different working conditions were analyzed, and the hydraulic performance of each part was evaluated. The factors that affected the stability of hydraulic turbines were identified, and their formation mechanisms and evolution laws were explored. The results show that the guide vane placement angle was reasonable in the guide vane area, and the hydraulic performance was fine. The impact on the stability of the hydraulic turbine was small. Further research showed that the hydraulic performance was poor in the runner area, and there were flow separation and detachment phenomena in the flow field. This created a channel vortex in the runner blade channel. The channel vortex promoted the lateral flow of water and had a significant impact on the stability of the hydraulic turbine. The diffusion section of the draft tube can dissipate most of the kinetic energy of the water flow in the draft tube area, and it had a good energy dissipation effect. However, the was a large pressure difference between the upper and lower regions of the diffusion section, and it generated a backflow phenomenon. It created vortex structures in the draft tube, and the stability of the hydraulic turbine was greatly affected.

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Section: Introductionmentioning

confidence: 99%

Study on Flow Characteristics of Francis Turbine Based on Large-Eddy Simulation

Xu,

Cheng,

Lin

et al. 2023

Water

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“…Yamamoto et al [15] inferred, based on the numerical calculation of two-phase flow, that the velocity distribution near the runner crown was extremely uneven and the high-vorticity region caused by the interaction between the high-speed region and the separation region was the cause of the inter-blade vortex. Based on experimental observations and calculations, Zhou et al [16] argued that the backflow of the draft tube at partial loads was the reason for the generation of the inter-blade vortex. Based on high-speed photography technology, Liu et al [3] claimed that the main reason for the generation of the inter-blade vortex was the influence of the large impact angle at the blade's inlet.…”

Section: Introductionmentioning

confidence: 99%

Particle Image Velocimetry Test for the Inter-Blade Vortex in a Francis Turbine

Jin²,

et al. 2021

Processes

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Hydropower units are usually operated in non-design conditions because of power grid requirements. In a partial-load condition, an inter-blade vortex phenomenon occurs between the runner blades of a Francis turbine, causing pressure pulsation and unit vibration, which hinder the safe and stable operation of power stations. However, the mechanism through which the inter-blade vortex generation occurs is not entirely clear. In this study, a specific model of the Francis turbine was used to investigate and visually observe the generation of the blade vortex in Francis turbines in both the initial inter-blade and vortex development zones. Particle image velocimetry was used for this purpose. In addition, we determined the variation law of the inter-blade vortex in the Francis turbine. We found that the size and strength of the inter-blade vortex depend on the unit speed of the turbine. The higher the unit speed is, the stronger the inter-blade vortex becomes. We concluded that the inter-blade vortex of such turbines originates from the pressure surface or secondary flow and stall of the blade at the inlet side of the runner at high unit speeds, and also from the backflow zone of the suction surface of the blade at low unit speeds.

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“…Magnoli et al [22] identify three independent vortical structures in a runner with numerical simulations, and the experimental measurements confirm that the pressure oscillation amplitude is drastically increased due to the set-in and development of inter-blade vortex. Besides, some investigations towards inter-blade cavitation vortex are performed by Kurosawa et al [23], Bouajila et al [24] and Liu et al [25].…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of inter‐blade cavitation vortex for a Francis turbine at part load conditions

Sun

Guo

Luo

2021

IET Renewable Power Gen

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Inter‐blade cavitation vortex at part load has raised significant concerns about operation stability for Francis turbines due to tremendous development and integration of renewable energy resources into power grid. The principal objective of this study is to investigate the flow characteristics of inter‐blade cavitation vortex and its influence on pressure fluctuations for a low‐head Francis model turbine. Unsteady numerical simulations are carried out using shear stress transport turbulence model and Zwart cavitation model. Numerical results yield to a good validation with the experimental data. The findings show that inter‐blade cavitation vortices highlighted by cavitation structure and vortex structure are extremely different at the points adjacent to the incipient line of inter‐blade cavitation vortex. The location of inter‐blade cavitation vortex development in the runner is more sensitive to rotating speed than that to guide vane opening. The formation mechanism of inter‐blade cavitation vortex is attributed to flow separation in the vicinity of the runner hub. Pressure fluctuations induced by inter‐blade cavitation vortex are directly associated with the evolution of vapour volume in the runner and feature wide‐band and low‐frequency characteristic, and the fluctuations on the suction side of the runner blade are significantly magnified because of the presence of inter‐blade cavitation vortex.

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Investigation of Channel Vortices in Francis Turbines

Cited by 7 publications

References 15 publications

Study on Flow Characteristics of Francis Turbine Based on Large-Eddy Simulation

Study on Flow Characteristics of Francis Turbine Based on Large-Eddy Simulation

Particle Image Velocimetry Test for the Inter-Blade Vortex in a Francis Turbine

Numerical investigation of inter‐blade cavitation vortex for a Francis turbine at part load conditions

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