Simulation Of Two-phase Flow And Optimization Based On CFD

Hydropower generation is an important part of China's energy and pumped-storage power stations have been an important target for development in recent years.Therefore,the safe and stable operation of pumped-storage units is a key subject of our research.CAD and CFD technology were used to firstly design the pump-turbine in three dimensions,The internal flow of pump turbine under the sand flow is investigated.The erosion of pump turbine under the action of sediment is deeply analyzed.This is of great significance to the improvement of the performance of the pump and turbine and the safe and stable operation of the generator set.The main research contents are as follows:(1)In order to explore the internal fluid behavior of pump turbine,In this thesis,four groups(Standard k-? ? RNG k-? ? Standard k-? and SST k-?)of turbulence models will be used for simulation calculation,0.5Q,0.75 Q,1.0Q,1.25 Q and 1.5Q were selected for the pump condition,under the opening of 16 mm,the external characteristics of pump turbine under pump condition are analyzed emphatically.The head,efficiency and shaft power of pump turbine are calculated,The results are compared with the measured data,the difference of simulation results of each turbulence model is compared.The results show that the model RNG k-? is suitable for the simulation calculation and performance evaluation.(2)The internal solid-liquid two-phase flow under standard turbine and pump conditions was explored.In the turbine and pump conditions,the eddy current calculation model with the model RNG k-? is used for simulation.Since the mesh is an assembly,interface setting is needed,in the interface processing part of Fluent,matching option is adopted,In the pump condition,the interface setting is the same as the water turbine condition.The experimental results show that the introduction of solid particles in the two working conditions will lead to negative pressure of the unit,and the unit is easy to produce serious wear.(3)Three-dimensional design software(Solid Works)is used to build solid models of pump turbine components,ICEM was used to divide the scroll casing into tetrahedral grid and the draft tube into structural grid,Turbo Grid is used for meshing symmetric rotating structures.The scroll casing and guide vane were modified and optimized by streamlining principle and reverse flow thinking,And compared with the model before optimization.The numerical simulation results show that: After optimization,the section area of scroll casing is increased,and the nose area is more streamlined;The modified fixed guide vane has better symmetry,And the velocity can be flow out axisymmetricly;The optimized flow components can improve the efficiency of pump turbine,and reduce the vibration of the unit.