Erosion Wear on the Runner Shroud of a Francis Turbine.

Erosion wear is an important issue for a Francis turbine operating on rivers from the Himalayas, which directly hinders the utilization of hydropower. In this research, the severe erosion wear on the runner shroud of a Francis turbine is studied. The characteristics and physical mechanisms of the erosion wear on the runner shroud are investigated through numerical simulation using commercially available software. The results show that the runner shroud experiences heavy erosion wear, especially in the outlet region where the particle impact velocity is the fastest. The cross-flow and interblade vortex in the blade channel are major contributors to aggravating erosion on the shroud. They change the motion of the particle and cause more particles to accumulate on the shroud. Furthermore, this effect is ultimately attributed to the forces on the particle when moving in these flows. In the cross-flow, particles impact the shroud near the inlet at a slow velocity due to the drag force. In the interblade vortex, the slow particles are attracted to move around the vortex due to the fluid stress force and virtual mass force; when the particles are moving around the interblade vortex, they tend to impact the shroud at a high speed. [ABSTRACT FROM AUTHOR]