Analysis of the Inlet Reverse Flows in a Pump Turbine Using 3-D Viscous Numerical Techniques

The purpose of this paper is to apply advanced technology to predict the phenomenon of reverse flows created at the inlet during pump operation of Francis type pump-turbines. The authors introduce 3-D viscous numerical techniques, which were developed for hydro-turbine runners several years previous, to predict and analyze the recirculation flows at the inlet during pump operation. The motions of the separation flows are predicted by reducing the discharge rate from design to off-design operation conditions. In order to accurately capture the strong vortex, a new boundary condition of turbulent parameters on the wall is introduced in this simulation. The computational results are found to be in reasonable agreement with the experimental results. The limitations of the k- ε two equations turbulent model in the application of vortex flows are discussed in this paper. Finally the authors present a basic scale for use with Navier-Stokes simulation techniques with k- ε two equations model when using the model as design tool in the case of reverse flows.