3D Numerical Simulation On Internal Flow Of A Francis Turbine In Sandy Water

Our country is rich of hydropower resources. Theoretically, the total hydropower resourceamount, the technically exploitative amount and the economically exploitative amount are689million kW,493million kW and395million kW, separately. Obviously, it is of considerablepotential and significance to develop hydropower in our country. As the core component of ahydropower station, hydraulic turbine plays a vital role in the overall performance of a station.Researches on the technology of hydraulic turbine are continuously deepening with thedevelopment of hydropower industry. Due to the natural environment of our country, there is alarge amount of sand in rivers. Statistically, the average annual sand content in Sanmenxiasection of Huanghe River has reached to37.6kg/m~3. As for Yangtze River, the average annualsediment runoff has achieved to514million ton one year, while the average annual content ofsand in Three Gorges reservoir area is1.17kg/m~3, and the maximum value reaches to10.5kg/m~3. What’s more, the sand entering the runner is about20kg/m~3at Liujiaxia HydropowerStation on Huanghe River. The sand erosion problem of flowing parts of a hydraulic turbinehas already been a subject that deserved to be studied in-depth. Therefore, the research andanalysis of internal flow field of hydraulic turbine in solid-liquid two-phase flow haveimportant theoretical and practical significance.By taking a Francis turbine as the research object, the3D geometrical model of the entireflow passage of this turbine was established. Its internal flow was numerically simulated byusing the CFD software. The internal flow conditions of this Francis turbine was analyzed bythe obtained computational results. Main achievements of this dissertation are listed asfollows:Firstly, the3D geometric models of the spiral case, guide vane mechanism, runner anddraft tube of the turbine were established according to the2D design drawings and actualhydraulic design parameters of the selected hydraulic unit by using Unigraphics6.0software.Then the file of the3D model of the turbine exported from UG with the format of ’parosolid’was imported into ANSYS ICEM CFD software, and mesh division and meshing qualityinspection of all flowing parts were conducted.Secondly, the mesh file exported from the ANSYS ICEM CFD software with the formatof ’cfx5’ was imported into ANSYS CFX software, then the boundary conditions of thecomputational models of all flowing parts of the turbine were set by applying the basic theory of computational fluid dynamics. The internal flow field distributions of all flowing parts ofthe turbine in clear water and sandy water were calculated.Thirdly, the calculation results were processed by the ANSYS CFX-POST software. Thevelocity vector distribution, pressure contour lines, and sand volume fraction distribution ofinternal flow of the turbine in some conditions were obtained, and the stream lines of variousoperating conditions were obtained. The velocity change, pressure change, flow state anddensity distribution were analyzed.Finally, the internal flowing characteristics in different operating conditions of thehydraulic turbine were compared and analyzed. The flowing information in the internal flowof various flowing parts was obtained. To some degree, the performance of the turbine wasquantitatively and qualitatively evaluated.