Effect of Guide Vane Clearance Gap on Francis Turbine Performance

Koirala, Ravi; Zhu, Baoshan; Neopane, Hari Prasad

doi:10.3390/en9040275

Cited by 28 publications

(14 citation statements)

References 4 publications

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“…Figure 1 shows the main geometrical parameters that are considered for the development of the guide vane cascade [4][5][6][7][8]. Primarily, the goal is to estimate the ranges for these parameters under the design conditions of the turbine.…”

Section: Geometry Descriptionmentioning

confidence: 99%

Constraints of Parametrically Defined Guide Vanes for a High-Head Francis Turbine

et al. 2021

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This paper is focused on the guide vane cascade as one of the most crucial stationary sub-systems of the hydraulic turbine, which needs to provide efficient inflow hydraulic conditions to the runner. The guide vanes direct the flow from the spiral casing and the stay vanes towards the runner, regulating the desired discharge. A parametric design tool with normalized geometrical constraints was created in MATLAB, suitable for generating guide vane cascade geometries for Francis turbines. The goal is to determine the limits of these constraints, which will lead to future faster prediction of initial guide vane configurations in the turbine optimal operating region. Several geometries are developed using preliminary design data of the turbine and are investigated using CFD simulations close to the best efficiency point (BEP) of the turbine. This research is part of the Horizon-2020—HydroFlex project led by the Norwegian University of Science and Technology (NTNU), focusing on the development of a flexible hydropower generation.

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Section: Geometry Descriptionmentioning

confidence: 99%

Constraints of Parametrically Defined Guide Vanes for a High-Head Francis Turbine

et al. 2021

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“…In addition, the loss of water head in the guide vanes was reduced，so as to improve the efficiency of the runner. Koirala et al (2016) numerically calculated the internal flow field of a Francis turbine. It was found that by increasing the end clearance of the guide vanes, the amount of flow that leaked through the clearance increased, and the unit efficiency was reduced.…”

Section: Introductionmentioning

confidence: 99%

Effect of Guide Vane Pitch Circle Diameter on Pressure Fluctuation in Vaneless Zone of Francis Turbine

2020

JAFM

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In a Francis turbine, the guide vanes are arranged in the direction of flow behind the stay vanes. And as it is generally believed that the outlet angle of water after it flows through the spiral case and stay vanes is fixed, the flow and flow circulation are altered by changing the opening of the guide vanes so as to change the output of the turbine. The rotor-stator interaction effect induced by the interaction between the guide vanes and the runner of the Francis turbine was one of the main causes of the pressure fluctuation. The effect of guide vanes placement on pressure fluctuation in vaneless zone of Francis turbine was studied. In this study, the commercial software ANSYS CFX16.0 was used for the three-dimensional numerical simulation of the whole flow passage of a Francis turbine model in a power station. The turbulence model used in the calculation was the shear stress transport (SST) model. The independence between the total number of computational meshes and the timestep was verified to ensure the reliability of the calculation results. Five schemes with different diameters of the guide vanes distribution circle were proposed including D0/D1 (guide vane pitch circle diameter /diameter of runner inlet) equaling to 1.119, 1.128, 1.138, 1.144, and 1.15. The steady calculation results showed that, when the turbine was operating under the design condition, D0/D1 increased from 1.119 to 1.15, and the turbine efficiency and output showed a monotonically increasing trend, with the efficiency increased by 0.17 percentage point and output increased by 3.91kw. Twenty monitoring points were set up in the vaneless zone between the guide vanes and the runner to collect pressure fluctuation signals in the vaneless zone. By analyzing the characteristics of unsteady pressure fluctuations in the vaneless zone under design conditions of the five schemes, the optimal position of the guide vanes was determined. The numerical results showed that the pressure fluctuation amplitude at monitoring points in the same axial direction increased gradually from the top cover to the bottom ring. When the unit operated under the design conditions, by increasing the guide vane pitch circle diameter, the rotor-stator interaction between the guide vanes and the runner domain was weakened, and the pressure fluctuation amplitude in the vaneless zone between the guide vanes and the runner was reduced, thereby the stability of unit operation was improved.

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“…In the aspect of numerical simulations studies, Koirala et al [9] used the Tabakoff erosion model to analyze the erosion in Francis turbines and studied the effect of the guide vane clearance gap on Francis turbine performance. A very thorough numerical investigation detailed by Tallman et al [10] showed the influence of clearance size on the leakage flow, vortex, and secondary flow.…”

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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Effect of Guide Vane Clearance Gap on Francis Turbine Performance

Cited by 28 publications

References 4 publications

Constraints of Parametrically Defined Guide Vanes for a High-Head Francis Turbine

Constraints of Parametrically Defined Guide Vanes for a High-Head Francis Turbine

Effect of Guide Vane Pitch Circle Diameter on Pressure Fluctuation in Vaneless Zone of Francis Turbine

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

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