Abstract
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.
Highlights
China is rich in water energy resources
The fluid phase was treated as a continuum by solving the Navier–Stokes equations, while the dispersed phase was solved by tracking a large number of particles through the calculated flow field
The number of particle trajectory per unit inlet area determines the distribution of particles in the horizontal and vertical direction along the inflow, which is very important in the study of the erosion characteristics of the end-clearance surfaces
Summary
China is rich in water energy resources. The country’s outstanding features include precipitous watercourses with a concentrated distribution for climate, its topography and other factors, which are very beneficial to the development of hydropower [1]. Turbines experience several unsteady sediment-laden flows where such flows contribute to erosion in the flow-passage walls of the guide vane clearance. Used the k-omega based Shear-Stress-Transport (SST) model and the Finnie and Tabakoff erosion models in ANSYS CFX to studied flow field and erosion wear on Francis Turbine components due to sediment flow, who found that erosion and efficiency loss both decreases with increase in particle shape factor. A previously validated multiscale model of erosion is presented by Leguizamón et al [13,14] to obtain erosion distribution and the erosion process of Pelton bucket impacted by a sediment-laden water jet. Through a comparison and analysis of the above references, few studies have been conducted on the turbulence characteristics and erosional mechanism at the end-clearance flow of guide vanes with a large eccentric shaft. Using the actual wear pattern of the unit, the turbulence characteristics and the wear mechanism of the guide vane were analyzed and studied
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