Numerical simulation of internal flows through the spiral casing and stay vanes

This paper analyzes the inflow and optimizes the design of the spiral casing and stay vanes in a Francis turbine. The three-dimensional numerical simulation of the hydraulic spiral casing for the Three-Gorges Francis turbine was based on the solution of Navier-Stokes equations with the standard κ-Ε turbulence model and the Euler equations. The simulation used body-fitted coordinates, a staggered grid and the SIMPLEC algorithm. Calculated results for the design operating condition were compared to experimental results. The improvement and optimization concept for the design of the spiral casing and stay vanes was put forward through the analysis of the non-uniform flow.