Hydro-abrasive erosion in Pelton turbines: Comprehensive review and future outlook

Hydropower is an important step towards a low-carbon society; however, its global potential is challenged by high sediment content in streams. In Pelton turbines, which are installed in high-head hydropower plants (HPPs), even fine particles cause substantial damage leading to reduced turbine efficiency and increased maintenance cost. This study reviews the complex problem of hydro-abrasive erosion in Pelton turbines, particularly advances in prediction of erosion and associated efficiency reduction, abrasive potential at a potential site, and mechanism of progressive erosion. For this purpose, the hydro-abrasive erosion in buckets and injectors of the Pelton turbines covering a wide range of design heads, capacities, sediment and operating conditions obtained from reported works were analysed. In the bucket, the cut-out, splitter and brim region are found severely affected due to erosion; while, nozzle outlet and needle tip region are majorly affected. The erosion in cut-out, widening of splitter, and distortion of jet from injector erosion are major reasons for Pelton turbine efficiency reduction. The synergic effects of erosion and cavitation is also presented. A modification in the erosion model for initial assessment of erosion potential at a site is proposed and its use for mitigation of erosion at untapped hydropower projects is also discussed. Finally, the optimization steps related to erosion at a site for both upcoming projects and operational HPPs are addressed in detail. In view of the projected increase in sediment yield from catchments due to climate change, this study provides insights into mitigating erosion in HPPs located in erosion-prone regions.