Numerical Investigation of Influence of Splitter Blades on Hydraulic Performance and Sediment Wear Characteristics of Francis Turbines
The challenge of wear induced by sediment stands as a focal concern during the operation of hydraulic turbines subjected to sediment-laden water flows.Wear of the flow passage components can lead to material losses,induce unstable flow,and even trigger mechanical vibrations,significantly impacting the safety,stability,and economic performance of the power stations.This study,based on particle transport model coupled with the modified Oka wall erosion model,employing numerical simulation techniques for two-phase water-sand flow,investigates the erosion characteristics of a high-head Francis prototype turbine equipped with an original runner and a runner enhanced with added splitter blades,the Oka wall erosion model is improved by modifying velocity index and the impact angle constant to obtain more accurate wall wear characteristics.The investigation reveals that under load conditions of 90％,65％,and 40％of the rated capacity,the hydraulic efficiency of the turbine with added splitter blades improves by 0.3％,0.5％,and 0.2％,respectively.In addition,the relative velocity near the head of the suction surface of the runner blade and the water outlet of the blade is reduced,and the vortex structure close to the pressure surface in the runner blade is significantly suppressed under the condition of 40％rated load.The maximum sediment erosion rate of the original runner blade occurs near the water outlet of the blade near the lower ring,and the wear intensity of the pressure surface of the blade gradually decreases with the decrease of load,while the erosion intensity between different working conditions of the suction surface is relatively close.The wear rate of the blade surface is significantly reduced by the new runner scheme of the split blade,which is related to the improvement of the flow structure in the runner and the reduction of the impact velocity of sediment particles on the runner blade.The study elucidates the mechanism by which splitter blades enhance the internal flow and wear characteristics of the turbine,providing valuable insights for optimizing turbines against sediment wear.
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