OPTIMAL POSITION OF THE TONGUE OF SPIRAL CASING OF THE FRANCIS TURBINE

In paper [8] a calculation is given for potential flow in the spiral casing of the Francis turbine for the given geometry of the spiral casing and the orientation of the tongue. We propose a method for the optimization of orientation of the tongue in the spiral casing of the Francis turbine. The optimal orientation of the tongue can be obtained from the condition when the velocities on the outlet of a spiral casing have the minimum distance from the given velocity. The formulation of the problem is mathematically correct and the numerical model is based on the finite element method. The influence of the fluid viscosity is partially included in the potential flow model through the circulation in three-dimensional double-connected domain which defines the spiral casing.