Flow field analysis and performance prediction of three-dimensional turbulent flow in francis turbine

To study the inner flow by numerical simulation method is an important way for optimum design of francis turbine. Based on the 3D time-average Navier-Stokes equations, k-ε model was used to simulate the 3D turbulent flow field of whole flow passage in the Francis turbine including guide wickets, runner and draft tube. The energy performance and cavitation performance were predicted from the simulation results, and the calculated data were compared with the results of hydraulic turbine model experiment. The calculation of turbine efficiency and the measured efficiency was very closed and the maximal relative error was 0.9%. The ratio between calculated initial cavitation coefficient and measured critical cavitation coefficient was 1.57-1.99, and was in line with reality. The results show that the method of combining the whole passage computing with single passage computing has higher calculation efficiency and accuracy, and is feasible and applicable to solve the engineering problems.