Design of Model Francis Turbine Runner for Performance Test against Sand Erosion

The turbine operating in the runoff river, especially in the Asian and an Andes mountain of South America are facing sand erosion problem. The rate of erosion increases during the monsoon periods due to an increase in concentration of sand particles. Sand erosion rate is depended on particle velocity, concentration, operating condition, impingement angle and hardness of substrate as well as erodent itself. The components of Francis turbine namelyguide vanes, faceplates, runner blades and seal rings are vulnerable parts to sand erosion. Several techniques have been practiced to overcome this problem. Sand erosion can be reduced by application of coating, optimizing turbine blade profile and increasing the size of settling basin. The application of the coating has been practiced in few hydropower plants in Nepal, but the results were not found favorable to economically acceptable level. It is always not possible to reduce sand erosion problem by increasing the size of the settling basin since geographical condition is not favorable to construct large settling basin and suspended particles with size less than 0.2 mm causes significant damage in hydraulic turbine. Turbine design with a new design philosophy is another alternative to reduce sand erosion in Francis turbine. The new design philosophy is based upon the past sediment data and operational condition of Jhimruk Hydropower in Nepal. This paper describes design of model Francis turbine runner for performance test against sand erosion. The methodology for selection of hydraulic similar model and its mechanical design is explained in this paper. The selection of procedure for suitable model runner is done in reference to laboratory test facility and International Electro-technical Commission (IEC). Then model Francis turbine runner is drafted in 3D design software. The initial mechanical design of turbine is based on the assumptions, which could provide adequate strength for model to test in lab using 3D drafting tool. The model runner is then exported to ANSYS software for further simulation under laboratory test conditions to study deflection and strength due to pressure. To observe the deformation due to pressure on designed model runner, FSI simulation has been performed.