Water Resources and Power

To solve the problem of large relative deviation and low prediction accuracy of discharge,torque and efficiency of the Francis turbine with splitter blades,which influenced by turbulence models and meshing schemes,ICEM CFD software was used in each operating condition(low flow,designed flow,high flow)and all components(spiral and guide vanes,runner,draft tube)to put forward four kinds of grid schemes.The S-A model with a faster convergence was adopted to preliminarily predict the hydraulic efficiency of water turbine for proving the independence of grid partition.Then,the third scheme was selected for further analysis.Five kinds of turbulence models(S-A model,standardκ-εmodel,RNGκ-εmodel,standardκ-ωmodel,SSTκ-ωmodel)were selected to calculate the predicted value of the flow rate,torque and hydraulic efficiency,which finds hydraulic efficiency with high prediction precision in all models but the flow rate and torque with a relative lower prediction accuracy.So,five other grid schemes were meshed again and S-A turbulence model was also used for preliminary analysis.It finds that this method can improve the prediction accuracy of the flow and torque,but the amplitude of enhancement is limited.Furthermore,RNGκ-ε,SSTκ-ω model,Realizableκ-εmodel and RSM model were used to predict flow rate and torque,the further improvement of flow prediction accuracy and torque appears,but still lower than the prediction accuracy of efficiency.The proposed prediction method can provide an important reference for the design and performance optimization of hydraulic machinery.