Comparative numerical analysis between two designs of Francis runner blades in sediment affected conditions

Abstract

Sediment erosion of hydraulic turbine is the major problem from the perspective of operation and maintenance in power plants of Himalayan and Andes region. The effects of sediment erosion on turbine components need to be predicted in advance during the design phase so that the best design with better sediment handling can be installed in real power plants. In this paper, comparison of performance and erosion of two different designs of Francis turbine i.e. design I and design II are carried out. Full turbine steady state numerical simulations are carried out for 8 different guide vane openings using shear stress transport (SST) k-ω turbulence model. Sediment erosion analysis is carried out using Tabakoff erosion model for both the designs, numerical hill charts are constructed using Ned and Qed values for all the operating conditions. Comparison of pressure distribution along pressure and suction side of GV surface between design I and a similar measurement in a previous experiment is carried out, which shows a good agreement between numerical and experimental results. Hydraulic efficiency and the sediment erosion rate density on the runner blades of design I for all operating conditions is higher than that of design II. The difference in efficiency is less than 1.85%for all operating conditions while sediment erosion rate density is much less in design II, which shows that design II is a better option for this turbine.