Hydraulic Optimization Design And Research Of Francis Turbine

As one of the renewable energy sources,hydropower resources have relatively low development costs,so it is of great significant to carry out the research related to hydraulic machinery.Our country's hydropower resources are abundant,but there are many silt laden rivers,most of the hydropower stations are plagued by silt wear,now running hydraulic turbines are designed under the condition of clear water,and the hydraulic turbines will deviate from the design working condition due to changes in the composition of the water in actual operation,which will cause the surface of the hydraulic turbines' blades to suffer from the combined action of cavitation erosion and sand wear,and cause serious threat to the stability and lifetime of the hydraulic turbine.According to the design conditions and requirements of high head,high speed and high sediment of a hydropower station,the selection of hydropower turbine's model and the design of each flow component are completed.Then according to the theory of fluid dynamics,the computational fluid dynamics(CFD)simulation software CFX was used to optimize the structure of the hydraulic turbine,and study its internal solid-liquid two-phase flow.The main works are as follows:(1)According to the original design parameters such as head H,flow Q,output P and sediment concentration given by the hydropower station and other related requirements,the selection of the hydraulic turbine's model and the determination of the main structural dimensions of each flow-through component(volute,stay ring and guide vanes,runner and draft tube)were completed,and 3D water body calculation model of the volute,stay ring and guide vanes,runner and draft tube were established.(2)Introduced the basic concepts of computational fluid dynamics and related governing equations,and some turbulence model theory and solid-liquid two-phase flow model theory commonly used in engineering practice,according to the actual working conditions of the hydropower station,complet the selection of the turbulence model and the two-phase flow model.Then,by using CFX software,the setting of the calculation method and the calculation domain's boundary conditions was completed.(3)Based on the numerical simulation method,the ANSYS CFX software was used to simulate the full-flow solid-liquid two-phase flow of the hydraulic turbine under design conditions,and the internal hydraulic loss calculation and other various hydraulic performance evaluations of the hydraulic turbine were completed.Then according to the overall hydraulic efficiency of the turbine,the distribution of the pressure on the front and back of the rotor's blades and the flow characteristics of the solid-liquid two-phase flow field in the full flow channel were obtained by calculating,the main structural parameters of the rotor blade(the laying angle of the water inlet,the laying angle of the water outlet and the thickness were modified and optimized,at the same time,the influence of the main structural parameters on the overall hydraulic performance of the hydraulic turbine was studied.(4)According to the actual operation of the hydropower station,three typical nondesign conditions were selected.Then,the numerical simulation method was used to calculate the full-flow solid-liquid two-phase flow of the hydraulic turbine's optimization model under each operating point selected.Finally,through comparative analysis,the twophase pressure distribution,two-phase velocity distribution and sand concentration distribution of each flow component of the hydraulic turbine designed in each operating point were predicted.