Unsteady Flow Simulation And Vortex Flow Diagnosis Of A Francis Turbine

There are many kinds of complex vortex flow inside fluid machinery. Research on the above phenomenons is very important for analyzing the essence of the complex flow, and explaining its evolution mechanism. Furthermore, the results can be used for engineering application. Complex and turbulent flow emerge inside a Francis turbine due to its special geometry structure. The studies on the interaction between flow vorticity field and solid surface, as well as the unsteady vortex flow have great significance for the improving of Francis turbine performance.The paper mainly focuses on the numerical simulation and flow diagnosis methods development for the inner flow inside Francis turbine. Firstly, an improved turbulent model for rotating machinery is derived, which is verified with experiment data through a computational example. Then, runner blade diagnosis method based on vorticity parameters is presented. The simulation results for different turbine models with two runners have been compared and analyzed, to study the flow pattern and energy loss performance for the turbine models.In this paper, two Francis turbine models with different runners for simulation are established, with three kinds of guide vane openings. The simulation results have been compared with experiment for verification According to the flow energy equations and turbulent viscous model, three dynamics parameters are defined used for the diagnosis on pressure fluctuation induced by vortex rope. Finally, the correlated dynamics parameters, which can affect the amplitude and main frequency of pressure fluctuation induced by vortex rope, are obtained by analyzing the simulation results.