3-D Viscous Flow Through Spiral Case with Stay Vanes

In order to maximize the hydraulic performance of a Francis turbine, the spiral case shall produce circumferentially uniform anguhr momentum adequate to the runner with the minimum stay vane wakes. Angular momentum in the spiral case can be assessed by the circumferential velocity V_(u-si) of the flow and the radius R_(si) at the stay vane inlet. Stay vane wake can be controlled by the incidence angle α_(si) of the spiral case flow to the stay vane inlet. A lumpsum flow analysis with CFD is indispensable to assess the 3-D viscous flow through a spiral case with stay vane.