A study of sediment erosion of runner seal of a Francis turbine

Suspended sediment particles included in working fluid of hydro turbines often cause erosion and reduce reliability and lifetime of the hydro turbine. It is important for understanding and suppressing erosion problems to understand characteristics of two-phase-flows of liquid and solid particles. In the present study, experimental and numerical studies were carried out to understand mechanisms of erosion in runner seal of a Francis turbine. The experiments were carried out using small-scale seal models. Flow patterns were visualized using coated mica flakes to understand entire flow patterns and a particle image velocimetry were also carried out to measure velocity field in a meridional cross-section. Accelerated erosion tests were also carried out and it was observed similar erosion distributions to that was observed in the actual hydro-turbine. Numerical flow simulations were also carried out to examine mechanisms of the erosion, contributions of each forces acting on the particles and appropriate parameters to capture characteristics of liquid-solid flows and erosion distribution, which were observed in experiments.