Swirl number based transposition of flow-induced mechanical stresses from reduced scale to full-size Francis turbine runners

Favrel, Arthur; Pereira, João Gomes; Müller, Andres; Landry, Christian R.; Yamamoto, Ken; Avellan, François

doi:10.1016/j.jfluidstructs.2020.102956

Cited by 27 publications

(19 citation statements)

References 43 publications

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“…At very low discharge, cavitation occurs inside the runner blade channels, exacerbating the pressure pulsations inside the runners [17]. In both high and low load conditions, cavitation in the draft-tube can lead to severe pressure pulsations [18,19], unstable or even resonant axial forces on the unit [20,21] and large torque fluctuations, which in turn can lead to power output oscillations [22,23]. For the runaway transients, the discharge will undergo a dramatic shift from high to low or even reverse direction, and the speed will also oscillate significantly [6], which means that the pump-turbine will alternate repeatedly in the unstable S-shaped region of the pump-turbine, and the above cavitation cavities are likely to appear and threaten the safety of the unit during the runaway process.…”

Section: Introductionmentioning

confidence: 99%

Evolution and influence of high-head pump-turbine cavitation during runaway transients

Wu¹,

Liu²,

Li³

et al. 2022

IOP Conf. Ser.: Earth Environ. Sci.

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Pumped-storage hydropower stations (PSHSs) play irreplaceable roles in promoting the stability and flexibility of power grids. Runaway process is one of the most dangerous transients for PSHSs, and the cavitation in the pump-turbine seriously affects the stability and safety of the unit. However, the evolution and influence of pump-turbine cavitation during runaway transients are still unclear. In this study, the runaway transients of a high-head pump-turbine considering the cavitation effects were simulated by using the three-dimensional (3D) computational fluid dynamics (CFD) method. The results show that the cavitation cavities in the runner appear and disappear periodically, influenced by the backflows around the leading and trailing edges of the runner blades. The wedge-shaped cavities near the leading edges occur around the peak rotational speed moment when the pressure pulsations in the vaneless space show the peak magnitude. And the tongue-shaped shaped cavities near trailing edges appear around zero discharge moment when the hydraulic radial forces reach the peak. The two types of cavitation occur at dangerous moments, to which attention should be paid in the preliminary design stage of PSHSs.

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Section: Introductionmentioning

confidence: 99%

Evolution and influence of high-head pump-turbine cavitation during runaway transients

Wu¹,

Liu²,

Li³

et al. 2022

IOP Conf. Ser.: Earth Environ. Sci.

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“…Jafarzadeh [10] used the water injection method to study the effect of the rotating vortex caused by the flow instability in the draft tube on the efficiency and wear of the turbine, and the optimization of the efficiency loss during the water injection process was analyzed. Favrel [11] proposed a method for evaluating the vortex behavior and associated pressure pulsations over the entire partial load operating range and analyzed the dynamic strain on the runner.…”

Section: Introductionmentioning

confidence: 99%

The Effect of J-Groove on Vortex Suppression and Energy Dissipation in a Draft Tube of Francis Turbine

Luo

Cong

et al. 2022

Energies

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The vortex rope in the draft tube is considered as the major contributor to pressure pulsation at partial load (PL) conditions, which causes the hydro unit to operate unstably. Based on the prototype Francis turbine HLA551-LJ-43 in the laboratory, J-grooves are designed on its conical section in this paper. We used numerical simulation to study the effect of the J-grooves on vortex suppression and energy dissipation in the draft tube. Four typical operating conditions were chosen to analyze the vortex suppression; the corresponding flow ratios Q* are 100%, 82%, 69%, and 53%, respectively. Entropy production theory is used to calculate the energy losses and assess the effect of the J-groove on energy dissipation under part-load conditions. By comparing entropy production, circumferential and axial velocity components, swirl intensity, pressure pulsation, and vortex distribution in a draft tube with and without J-grooves at different operating conditions, it can be concluded that the entropy production on the wall containing a conical section with J-grooves is obviously smaller than that without J-grooves, the effects of J-grooves on reducing circumferential velocity component Vu, pressure pulsation, and weakening vortex intensity and vortex rope in the conical section are obvious, especially at part load and deep part-load operating conditions. Using J-grooves shows better performance on vortex control and energy dissipation in the draft tube of a Francis turbine at partial load conditions.

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“…Guo Tao et al [12] studied the evolution of the channel vortex under part-load conditions using the large eddy simulation (LES) method based on the Vreman Processes 2021, 9, 1385 2 of 16 subgrid-scale stress model, and the results they gained showed that the instability and rupture of the channel vortex increases the pressure fluctuation of the blades. K. Yamamoto et al [13][14][15][16] used visualization PIV technology to conduct experimental observations on a channel vortex, analyze its development mechanism, and estimated its generation area. Guo Pengcheng et al [17][18][19] carried out experiments with numerical models on Francis turbines to analyze the development mechanism of channel vortices and made a comparative analysis of the shapes of cavitation vortices inside the channel by using said models in experiments.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Channel Vortex and Cavitation Performance of the Francis Turbine under Partial Flow Conditions

2021

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To realize a multienergy complementary system involving hydropower and other energy sources, hydraulic turbines frequently run under partial flow conditions in which a unique flow phenomenon, the channel vortex, occurs in the runner, causing fatigue failure and even cavitation to the turbine blade. Cavitation severely shortens the service life of the unit and terribly limits the output of the turbine under partial flow conditions. In this paper, a numerical model of a Francis turbine was created with tetrahedral grids; the large eddy simulation (LES) method based on the WALE subgrid scale model and the Schnerr–Sauer cavitation model was adopted to carry out numerical simulation of the Francis turbine; and a vortex identification method based on the Q criterion was used to capture and analyze the channel vortex. The calculation results showed that a negative impact angle at the inlet of the runner occurred when the turbine ran under partial flow conditions, leading to three different types of channel vortexes in the blade channel. Also, different channel vortexes caused cavitation on different positions on the runner, and the volume change of cavitation showed periodic properties.

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Swirl number based transposition of flow-induced mechanical stresses from reduced scale to full-size Francis turbine runners

Cited by 27 publications

References 43 publications

Evolution and influence of high-head pump-turbine cavitation during runaway transients

Evolution and influence of high-head pump-turbine cavitation during runaway transients

The Effect of J-Groove on Vortex Suppression and Energy Dissipation in a Draft Tube of Francis Turbine

Analysis of Channel Vortex and Cavitation Performance of the Francis Turbine under Partial Flow Conditions

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