Internal flow and loss mechanisms of specific speed 160 m-kW shroudless hydro turbine

High efficiency and low-cost hydro turbines are becoming more popular for medium and small-scale hydropower generation in underdeveloped locations. Because of this, a shroudless hydro turbine of medium specific speed 160 [m-kW] was developed based on a low specific speed 80 [m-kW] design concept previously studied in the author's laboratory. We are aiming to develop an optimal design method and further improve performances of the medium- specific speed 160 [m-kW] shroudless hydro turbine. The most important factors are the internal flow and the loss mechanism of each flow path component. In this study, the internal flow and loss mechanisms were investigated and clarified by experimental and computational approaches. The main loss mechanisms in the double circular cascade is the high swirling strength vortices extending from the guide vane inlet to the outlet near the end wall of guide vanes. Furthermore, it has been found that the interference of the secondary flow and leakage flow, and the tip leakage vortex are the predominant loss mechanisms of the shroudless runner.