Study On Cavitation And Wear Of Turbine Runner In High Sediment Content Water

In nature,water flows often carry suspended sediment,solid particles and other impurities.There are many rivers in China,and most of the rivers have relatively high sand content.Turbines run on these muddy rivers all year round,and the unit components are very vulnerable to wear and damage.The runner is the core water-conducting part of the hydraulic turbine,and its structure is relatively complicated,and it is also the part with the most wear and tear.Under the condition of sandy water,the turbine runner will suffer cavitation damage,sediment erosion and abrasion damage under the combined action of cavitation and sediment wear.The damage of components will not only affect the hydraulic performance of the unit,reduce the overall operating efficiency,seriously shorten the service life,and even cause the entire unit to stop running,causing huge electrical and economic losses to the hydropower plant.Therefore,the study and analysis of the wear of the turbine runner under the conditions of sand and water flowing can provide a certain reference for the protection of the turbine and the actual engineering design.In this paper,the Francis turbine of the Muzati Three-stage Power Plant in Aksubay,Xinjiang as the research object.Through the CFX fluid analysis software,under the conditions of clean water and sandy water medium,the steady numerical simulation of steam-liquid two-phase,solid-liquid two-phase and vapor-solid-liquid three-phase were carried out for hydraulic turbine under different guide vane opening,sediment particle size and sediment concentration.The cavitation,sediment erosion and abrasion of the turbine runner are further analyzed.The main research work and results of this article are as follows:(1)According to the basic parameters of the turbine and the design drawings of each flow part,using UG8.0 three-dimensional modeling software to establish a three-dimensional flow channel water model of the turbine volute,fixed guide vanes,movable guide vanes,runner,and draft tube.The unstructured meshing method is adopted.Then use ANSYS ICEM software to perform mesh division and mesh quality inspection on the 3D water model of each component,and set the boundary type.(2)Using CFX fluid analysis software to perform numerical calculations on hydraulic turbines with different guide blade openings under clear water conditions,and analyze the cavitation of the runner according to the pressure cloud diagrams and cavitation volume fraction diagrams of the runner components.The results show that with the increase of guide blade opening,the overall pressure of the runner gradually increases,the negative pressure area and the cavitation area gradually decrease,and the cavitation is serious in most areas near the water inlet of the runner,the bottom of the drainage cone,the inlet water edge of the blade and the outlet water edge of the blade near the lower ring.(3)Under the condition of medium with high sediment content,the numerical simulation of solid-liquid two-phase flow is carried out for the hydraulic turbine,to analyze the sediment wear of the turbine runner under different sediment diameters and different sediment volume concentrations.The numerical results show that the pressure value of each component of the runner increases first,then decreases and finally become stable under different sediment particle diameters.At different sediment concentrations,the pressure value of the runner increases with the sediment concentration.For sediment erosion,the sediment volume fraction of the runner area increases with the increase of the sediment particle size and concentration,and the degree of abrasion gradually increases under different sediment particle size and concentration.,and the degree of wear also gradually increases.The runner is easy to be worn by sediment near the upper crown and the lower ring near the water inlet of the blade face.(4)Under the condition of medium with high sediment content,the numerical simulation of vapor-solid-liquid three-phase flow is carried out for the hydraulic turbine,and studied the interaction between sediment erosion and cavitation under different guide blade openings and different sediment concentration,and get the abrasion of the runner under different working conditions.The calculation results show that the pressure of each component of the runner in sandy water is greater than that in clean water.The existence of sediment promotes the development of cavitation,and the existence of cavitation intensifies the wear of sediment.At the junction of the runner blades with the lower ring and the upper crown,the inlet water side is close to the lower ring and the outlet water side of the blade will cause serious abrasion,which is basically consistent with the wear of the turbine blades of the hydropower station in actual engineering.