Sediment erosion in guide vanes of Francis turbine: A case study of Kaligandaki Hydropower Plant, Nepal

Koirala, Ravi; Thapa, Bhola; Neopane, Hari Prasad; Zhu, Baoshan; Chhetry, Balendra

doi:10.1016/j.wear.2016.05.013

Cited by 51 publications

(24 citation statements)

References 2 publications

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“…The results depict that velocity difference between particle and water is not large in the flow passage of Francis turbine. This agrees well with the previous studies of liquid-solid two-phase flow performed with fine particles [9,26]. Near the runner blade, the velocity of solid phase is slower than that of liquid phase.…”

Section: Flow Prediction For Solid Phasesupporting

confidence: 92%

Sediment Erosion Prediction for a Francis Turbine Based on Liquid-Solid Flow Simulation Using Modified PANS

Cando¹,

Huang²,

Valencia³

et al. 2018

World Congress on Mechanical, Chemical, and Material Engineering

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A challenge in the prediction of the sediment erosion is the proper estimation of the motion and velocity of the solid particles, where Reynolds average Navier-Stokes (RANS) methods show limited resolution to determine the motion of solid phase affected by flow fluctuations. The present study adopts a modified partially averaged-Navier Stokes (PANS) method to analyse the sediment erosion prediction for Francis turbines. Numerical simulations were carried out to obtain liquid-solid two-phase flow information in entire flow passage of a Francis turbine using Eulerian-Lagrangrian approach. The hydraulic performance such as efficiency and discharge of the turbine achieved experimentally, are used to validate the present simulation method. The results show that the modified PANS model can improve the prediction accuracy and the smallest unresolved-to-total ratio of turbulence kinetic energy, fk, decided with the consideration of the difference between local average grid size and smallest grid size shows a slight accuracy improvement. Based on the two-phase flow field, sediment erosion was predicted in stay vane, guide vane and runner using a semi-empirical equation obtained from an erosion experiment of liquid-solid flow. It is noted that higher physical resolution captured by the turbulence model causes a diminution of the sediment erosion predicted. Further, the numerical simulation reveals that sediment erosion in stay vane is lower than guide vane and runner, whereas the highest values of the erosion intensity occurs in the runner. The sediment erosion due to fine solid particles in the turbine is mainly resulted from cutting. However, high sediment erosion due to deformation is also produced at the leading edges of stay vane and guide vane.

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Section: Flow Prediction For Solid Phasesupporting

confidence: 92%

Sediment Erosion Prediction for a Francis Turbine Based on Liquid-Solid Flow Simulation Using Modified PANS

Cando¹,

Huang²,

Valencia³

et al. 2018

World Congress on Mechanical, Chemical, and Material Engineering

View full text Add to dashboard Cite

show abstract

“…This can be severe in the context of hydropower plant operating with very high sediment concentration in Nepal. It was reported that size of clearance gap was around 10 mm at some locations of Kaligandaki 'A' hydropower plant Nepal, due to sediment erosion (Koirala, Thapa, Neopane, Zhu and Chhetry, 2016). In a similar study, erosion depth up to 35 mm at some locations of GV of Bhilangana HPP, India was observed (Acharya et al, 2019.…”

Section: Ctpmentioning

confidence: 70%

“…The increase in the size of clearance gap due to erosive wear reduces the overall efficiency of the turbine Koirala, Thapa, Neopane, Zhu and Chhetry, 2016). Figure 2 shows the efficiency measurement of Francis turbine with different size of clearance gaps.…”

Section: Ctpmentioning

confidence: 99%

Numerical Investigation of the Effects of Leakage Flow From Guide Vanes of Francis Turbines using Alternative Clearance Gap Method

2020

JAFM

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Flow around the Guide vanes (GV) in Francis turbine differs with the shape of hydrofoils. The difference in the pressure of fluid travelling to pressure side and suction side of GV contributes to flow behavior. This study presents the numerical technique using alternative clearance gap method to predict the flow around GV and its consequent effect on turbine performance. GV profile has a significant effect on the performance of the turbine with sediment contained fluid flow. In this paper, symmetrical NACA 0012 and cambered NACA 2412, NACA 4412 hydrofoils are studied introducing 0 mm, 2 mm, and 4 mm clearance gaps. Vortex filament can be seen when fluid leaves the clearance gap due to the leakage flow occurring through the gap. The intensity of vortex leaving clearance gap rises with an increase in the size of the clearance gap. However, in the case of asymmetrical GV profile, the velocity of fluid travelling along the vortex compared to that of symmetrical hydrofoil is lower. In case of low specific speed Francis turbines, this vortex is found to be a major reason to erode the runner surface due to high velocity of a sand particle travelling with them. With the alternative clearance gap approach, this paper compares the pressure pulsation downstream of GVs contributed by leakage flow for three NACA profiles, whose frequency is half of blade passing frequency.

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“…In addition, the influence of end-clearance on turbine efficiency was studied, where the loss in efficiency is greater than the increase of leakage flow. Koirala [16] showed that high quartz content, inefficiency of the flushing system, higher concentration of sediment load, high impingement velocity, and operation at low guide vane angles were the major contributors to sediment erosion in guide vanes. The end-surface clearance flow of the turbine guide vane was simplified as circular-cylinder flow and backward-facing step flow by Han [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Sediment Erosion Characteristics and Mechanism on Guide Vane End-Clearance of Hydro Turbine

Chen

Han

et al. 2019

Applied Sciences

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Sediment erosion caused by the collision of solid particles is a challenge for the safety, reliability, unit efficiency, and vibration noise of the hydroelectric engineering system located at China’s Yellow River and northwest inland basin. The sediment-laden flow of the guide vane end-clearance of the Francis Turbine at Dongshuixia hydroelectric station was used as the research object, and the large eccentric shaft structure of a guide vane was considered. Numerical calculations with the large eddy simulation (LES) and discrete phase models (DPMs) were carried out to study the erosion characteristics and mechanism of the end-surface of the guide vane and head cover, the flow mechanism of adverse erosion behind the shaft, and the influence law of the turbulence integral scale, turbulent kinetic energy, and turbulent flow angle on erosion. The flow field with a 1 mm clearance should set the number of particle trajectory per unit inlet area at about 1/mm2 to ensure the accuracy of calculation. The von Kármán vortex street is the main reason for adverse erosion behind the shaft and the low frequency energy of the turbulence plays a leading role in erosion. The above results provide a reference for the optimization design of an anti-wear guide vane and wear-protection of the clearance with sediment-laden water.

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Sediment erosion in guide vanes of Francis turbine: A case study of Kaligandaki Hydropower Plant, Nepal

Cited by 51 publications

References 2 publications

Sediment Erosion Prediction for a Francis Turbine Based on Liquid-Solid Flow Simulation Using Modified PANS

Sediment Erosion Prediction for a Francis Turbine Based on Liquid-Solid Flow Simulation Using Modified PANS

Numerical Investigation of the Effects of Leakage Flow From Guide Vanes of Francis Turbines using Alternative Clearance Gap Method

Sediment Erosion Characteristics and Mechanism on Guide Vane End-Clearance of Hydro Turbine

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