Numerical Simulation And Analysis Of Internal Flow Of Francis Turbine In Sandy Water

Compared with other types of energies, hydroelectric power has lots of advantages like advanced technology, small impact on the environment, and large comprehensive benefits. The priority has been given to the development of hydroelectric power in the world. However, the rivers in China have large sediment concentrations. When working in those rivers, turbines would be destroyed by sand particles and the shape of the flow components will be changed. This will lead to reduced efficiency, intensified vibration, frequent maintenance, and extended overhaul, and a series of indirect consequences.The study of sandy water flow in turbines is the basis in the study of sand erosion. Therefore, it is of great significance to study the flow characteristics in turbines in solid-liquid two-phase flow. Practices have proved that, the installation of short blades in the runner can reduce the sand erosion problem when Francis turbines are working under the high head conditions. However, the function of short blades shall be further studied.By taking a low specific speed Francis turbine as the example, the numerical simulation software CFX was used to study the pressure and sediment distributions in the flow components of conventional runner and the runner with long and short blades under different conditions. The simulation results show that the installation of short blades in the runner can reduce the sand erosion.The main works are as follows:1. According to the parameters of the Francis turbine, the flow components of the turbine were modeled by UG, and then the established models were saved as the format of Parasolid. The meshes were generated in ICEM.2. The generated mesh files were imported into ANSYS CFX-Pre software for physical definition and condition setting. The software CFX-Solver was used for numerical simulation. The internal flow fields of various flow components with or without short blades were obtained when the particle and volume concentration are constant while the flow rate is changing.3. The calculation results were processed by the CFX-Post software. By comparing and analyzing the obtained pressure distributions and sediment concentrations, the flow patterns were analyzed.4. By combining the simulation results and the theoretic knowledge, the effect of the short blades on the turbine performance in sandy water was qualitatively analyzed.