Pelton turbine needle eccentricity leading to asymmetric hydro-abrasive erosion

Abstract Hydropower generation of turbines located near geologically young mountain ranges like the Himalayas is challenged by incoming sediment particles. Pelton turbines installed at high heads are significantly affected by hydro-abrasive erosion due to high flow and erosion velocities. The injector of the Pelton turbine is one of the major components of the Pelton turbine affected by hydro-abrasive erosion. Improper installation or manufacturing defect leads to needle eccentricity causing an asymmetric erosion pattern of the injector, thereby reducing jet quality. Here, the effect of needle eccentricity on hydro-abrasive erosion of the injector is numerically investigated by tracking the sediment particles using the Discrete Phase Model (DPM). The intensity and asymmetricity in the erosion of the needle increases with an increase in needle eccentricity. Similar behaviour in the erosion of the needle is observed in reducing the nozzle opening of the eccentrically displaced needle. For a perfectly aligned needle, the average erosion rate in both the upper and lower half region of the needle was identical. However, with 8% of needle eccentricity, the average erosion rate in the upper half region of the needle i.e., towards the displaced side was 89% more compared with the lower half region of the needle. The study emphasises the necessity of inspecting the needle alignment, particularly post-maintenance to mitigate the detrimental effects of hydro-abrasive erosion on Pelton turbine performance.