Numerical Simulation Of Two-Phase Internal Flow And Silt Erosion In Francis Turbine

As a core part of the hydroelectric system, hydraulic turbine plays a decisive role in the overall performance of the hydroelectric system. China has abundant water resources, but many rivers have high sediment concentrations. This sandy water will damage the turbine parts. Therefore, it is important to study the turbulent flow characteristics of the turbine in sandy water, and to predict the erosion of various flow components.The three-dimensional flow inside the flow passage of a Francis turbine unit was numerically simulated. The calculation model was the prototype turbine. The flow characteristics of this unit under different flow conditions and different particle sizes were calculated, it shows that the flow characteristics are good under the design condition, sand percentage is higher under bigger particle sizes. Based on the experienced formula and the CEL function in CFX, the erosion of turbine runner was visually analyzed. The average wearing capacity of the runner parts was predicated. Main works completed are as follows:1. According to the 2D design drawings of this Francis turbine, the 3D water models of spiral case, guide vane mechanism, runner and draft tube were established by using CATIA.2. Based on unstructured mesh generation method, ANSYS ICEM was used to generate meshes of various components and set the boundary conditions.3. The CFX-Pre was used to set the boundary conditions, select parameters, solve and control of various components. The CFX solver was used to calculate the 3D turbulent flow in the turbine under different inlet flows, different particle sizes and different particle percentage.4. The CFD-Post was used for post-processing of the calculation results to obtain the pressure distribution and sediment volume concentration of various flow components under different conditions. Meanwhile, based on the experienced formula and the CEL self-defining function in CFX, the erosion of turbine runner parts was visually analyzed.5. By comparing and analyzing the calculation results under six operating modes, it shows that the flow characteristics are good under the design condition. In this condition, the sediment concentration is small and the erosion degree of runner parts is less, which can provide certain references for project design.