Analytical modelling and mechanism of hydro-abrasive erosion in pelton buckets

摘要

Hydro-abrasive erosion, a severe issue in hydraulic turbines, is caused by sediment laden flow leading to shutdowns and losses. In this study, a simplified analytical model is developed which describes the relationship of hydro-abrasive erosion in Pelton buckets with sediment properties, erosion velocity, turbine material property and duration of erosion. This model has been validated by comparison with both experimental measurements and literature, and shows strong agreement for most of the parameters. Further, mechanism of erosion in various parts of the buckets made of 6 types of material (3 types of steel, 2 coatings and bronze) were analysed from scanning electron microscope (SEM) images. The mechanism of erosion in different parts of Pelton buckets was found to be strongly related with the flow pattern in that part. The metallic turbine buckets showed plastic deformation whereas coatings showed crack formation initiating material removal. The study shall be useful for design and material experts working in the field of hydraulic machinery.