Study Of The Diversion Separator About The Impact Of The Flow Characteristics Of The Draft Tube In Sandy Water

Hydraulic turbine is one of the key components in the hydroelectric power system, and it plays an important role in the overall efficiency of the system operation. In recent years, the theoretical research and experimental research of turbine gradually mature along with the development of hydropower cause. At the same time, there are still many hydropower stations with abnormal conditions of the unit due to some technical problems which can not be solved at present or to be solved. These conditions lead to the damage of turbine flow components, especially the effect of hydraulic vibration of draft tube on the stable operation of the turbine. So it is particularly important to study the flow conditions in the draft tube, especially for turbines running in sandy river.Based on this, a Francis turbine of a hydropower was taken as the research object. The solid-liquid two-phase flow in the whole flow passage of this turbine was numerically simulated by using CFD. The internal flow fields after installing diversion plate at different locations were analyzed under different conditions. The velocity distribution, pressure distribution, sediment concentration, and others were calculated. The hydraulic performance was discussed, which will provide references for future study and optimization of draft tube vibration in sandy water.Main works of this dissertation are as follows:1. On the basis of two-dimensional design drawings of the Francis turbine, the 3D model of the whole flow passage of the turbine was established by using UG software. The model components include spiral case, stay ring, runner and draft tube. Then the established 3D model was imported into ICEM which is a meshing module in ANSYS. Appropriate mesh parameters were set, and the quality of grids was verified.2. The grid files of various flow components were imported into the pre-processing software CFX in ANSYS. Various calculation domains were set according to corresponding principles of fluid dynamics, including initial boundary conditions, interface boundary conditions, inlet and outlet boundary conditions, wall and other settings.3. The control conditions of solution were set to numerically simulate the internal flow of the calculation model under different conditions.4. According to the calculation results, the flow conditions in the draft tube without the diversion plate were compared with that with the diversion plate. The results show that the installation of diversion plate can improve the flow regime in the draft tube and reduce hydraulic vibration through cutting the vortex strip.