Experimental and Numerical Investigations of Erosion on Runner Seal of a Francis Turbine

To suppress sediment erosion in labyrinth seals is an important problem for hydro turbine design and operation. A numerical simulation was carried out to know the flow with solid particles and its influence on the erosion in the labyrinth seal. The result showed that the vortex took place in the intermediate space between the first and the second seal gaps and the solid particles impinged on the runner wall along the vortex. Experiments were also carried out to understand the characteristics of the flow with vortices in the labyrinth seal by changing the flow rate of the leakage through the seal. It was found that the vortex took place stably in the intermediate space regardless the flow rate of the leakage although the Taylor vortex pattern was significantly disturbed as the leakage flow rate increased.