Influence of Hydraulic Design on Stability and on Pressure Pulsations in Francis Turbines at Overload, Part Load and Deep Part Load based on Numerical Simulations and Experimental Model Test Results

Magnoli, M V; Maiwald, Maria Isabelle

doi:10.1088/1755-1315/22/3/032013

Cited by 19 publications

(8 citation statements)

References 1 publication

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“…Experiments have shown that blade channel vortices create large pressure fluctuations near the runner outlet, which affect the stability of units (Dörfler et al , 2012). In recent years, many simulation results have been reported about blade channel vortices (Xiao et al , 2011; Kurosawa et al , 2010; Magnoli and Maiwald, 2014; Zuo et al , 2015; Wack and Riedelbauch, 2015). Most of them showed that the high positive incident angle was the main reason for this phenomenon (Chen and Peng, 1999; Xiao et al , 2011).…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of the blade channel vortices in a Francis turbine runner

Zhou

Liu

Wang

et al. 2017

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Purpose This study analyzes the blade channel vortices inside Francis runner with a particular focus on the identification of different types of vortices and their causes. Design/methodology/approach A single-flow passage of the Francis runner with refined mesh and periodic boundary conditions was used for the numerical simulation to reduce the computational resource. The steady-state Reynolds-averaged Navier–Stokes equations closed with the k-ω shear–stress transport (SST) turbulence model were solved by ANSYS CFX to determine the flow field. The vortices were identified by the second largest eigenvalue of velocity. Findings Four types of vortices were identified inside the runner. Three types were related to the inlet flow. The last one (Type 4) was caused by the reversed flow near the runner crown and had the lowest pressure inside the core near the runner outlet. Thus, in the blade channel vortex inception line, Type 4 vortex would appear earlier than the other three ones. Besides, the Type 4 vortex emerged from the crown and shed toward the blade-trailing edge. And its location moved from near the crown down to near the band when the unit speed increased or unit discharge decreased. Research limitations/implications Although the refined mesh was used and the main vortices in the Francis runner were well predicted, the current mesh is not enough to accurately predict the lowest pressure in the channel vortex core. Practical/implications This knowledge is instructive in the runner blade design and troubleshooting related to the channel vortex. Originality/value This study gives an overview of the main observed blade channel vortices and their causes, and points out the important role the reversed flow plays in the formation of blade channel vortices. This knowledge is instructive in the runner blade design and troubleshooting related to blade channel vortices.

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Section: Introductionmentioning

confidence: 99%

Numerical simulation of the blade channel vortices in a Francis turbine runner

Zhou

Liu

Wang

et al. 2017

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“…As for hydro turbine, the secondary flow involved blade wake often sheds and curls up to the downstream to induce turbulence eddy and swirl to the draft tube. This deteriorates the hydraulic performance in the offdesign conditions at the full load [3,4,5,6] as well as the part load [7,8].…”

Section: Introductionmentioning

confidence: 99%

“…For those turbines fitted to lower head, the introduction of foreign structures [8,10] and water jet [11] was part of the successful solutions. In this paper, medium head Kaplan type turbine is focused.…”

Section: Introductionmentioning

confidence: 99%

Design of a Kaplan turbine for a wide range of operating head -Curved draft tube design and model test verification-

Matsumoto

Ohtake

et al. 2016

IOP Conf. Ser.: Earth Environ. Sci.

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“…In recent years, based on existing research results, scholars in the world have further carried out numerical simulation and experimental research on the pressure pulsation of hydraulic turbines. Based on numerical simulation and model tests, the stability and pressure pulsation of Francis turbines under overload, part load, and deep part load were studied by Maiwald [15]. The results showed that different runner structure designs can affect the pressure pulsation level in the unit.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Flow Field Characteristics and Pressure Pulsation in Horizontal Axis Double-Runner Francis Turbine

Yang

et al. 2021

Water

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Horizontal axis double-runner Francis turbines have great advantages in the development of small hydropower plants, but the arrangement of double runners aggravates the complexity of the water flow between runners, and the mutual influence of the two runners cannot be ignored. In order to explore the relationship between the performance and the internal flow field and investigate the pressure pulsation characteristics of the double-runner Francis turbine, the steady and unsteady numerical analysis of the full flow channel of a prototype turbine was carried out based on the Realizable k-epsilon model and the polyhedral mesh method. The results show that the relationship between the average efficiency of the two runners and the flow difference between the runners is negatively correlated. As the flow rate difference between the runners on both sides increases, the average efficiency of the runners decreases. The draft tube flow of a horizontal-axis turbine has a profound effect on the flow field characteristics in the runner. When the working conditions change, the turning and converging timing of the mainstream at the outlet of the two runners will change. The movement of the mainstream promotes the change in location of the dead water zone. The existence of the vortex zone makes the pressure distribution at the outlet of the runner uneven, which is an important reason for the asymmetry of the flow in the runner. The analysis of pressure pulsation and its frequency spectrum shows that when the working conditions change, the low-frequency, strong pressure pulsation area on the surface of the guide vane will regularly migrate between the two runners, while the high-frequency pressure pulsation that occurs in the bladeless zone will dissipate in the runner. The doubling of the blade frequency on the pressure surface and back surface of the blades gradually attenuates with the increase of frequency. The pressure pulsation attenuation on the surface of the high-position blade conforms to the linear law, and the attenuation of the pressure pulsation on the surface of the low-position blade conforms to the exponential law. The research in this paper provides a certain reference value for revealing the flow field mechanism and pressure pulsation characteristics of the double-runner Francis turbine.

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Influence of Hydraulic Design on Stability and on Pressure Pulsations in Francis Turbines at Overload, Part Load and Deep Part Load based on Numerical Simulations and Experimental Model Test Results

Cited by 19 publications

References 1 publication

Numerical simulation of the blade channel vortices in a Francis turbine runner

Numerical simulation of the blade channel vortices in a Francis turbine runner

Design of a Kaplan turbine for a wide range of operating head -Curved draft tube design and model test verification-

Analysis of Flow Field Characteristics and Pressure Pulsation in Horizontal Axis Double-Runner Francis Turbine

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