NUMERICAL SIMULATION OF EROSION WEAR OF THE FRANCIS TURBINE RUNNER BLADES

Francis turbines are a common solution for high head hydraulic power plants using mountain rivers energy. Due to a high concentration of sediments in such rivers, a lifetime of hydraulic turbines of this type is determined mainly by erosion wear factor. Considering previous operation experience of power plants of this type is important in new construction or reconstruction, modernization of hydraulic power plants and installation of new equipment. The article presents the numerical simulation analysis of a two-phase flow in a high head Francis turbine operating at a low specific speed to evaluate erosion wear of runner blades using Tabakoff-Grant model at various operating modes and sediment mass flow rates. We show that the value of erosion wear is mainly associated with the values of local flow rates, the most damaged areas are the leading and trailing edges of the blade, as well as the pressure side of the blade. The results confirm the linear dependence of Francis turbine runner blade erosion on the amount of sediments. We determined that the new hydraulic equipment made of stainless steel instead of regular carbon cast steel may not sufficiently increase intervals between overhauls.