Development of rotating disc apparatus for test of sediment-induced erosion in Francis runner blades

•Rotating disc apparatus is developed for sediment erosion test in Francis blades.•Francis runner blades designed by traditional methodology are used as test specimens.•Erosion pattern observed is similar to that observed in real hydropower plant.•Erosion pattern is similar to that predicted from CFD analysis in earlier studies.•Traditional designs of Francis turbines are highly prone to sediment damages.

Sediment erosion in hydraulic turbines has been a major challenge in development of hydropower projects in Nepal. The hard abrasive material present in the river water of this region cause rapid erosion of turbine components and affect the performance of turbines, which in turn decreases the efficiency, reliability and operating life of such projects. There is a need of a new design methodology to develop turbines to resist erosion in high sediment conditions. The first step towards such development would be to investigate different design options in laboratory, which needs a standard methodology to carry out sediment erosion test in controlled environment. This study is focused on design and development of a laboratory test setup suitable for carrying out sediment erosion test in Francis runner blades. A test rig called rotating disc apparatus has been developed and installed in Turbine Testing Laboratory, Kathmandu University, Nepal, which uses Francis runner blades as test specimens. The test carried out in this setup has shown that the Francis turbines designed with traditional design methodology is highly prone to loss of material due to sediment erosion.