Development of an ultra-low head siphon hydro turbine using computational fluid dynamics

Highlights: • An Ultra-Low Head Siphon Hydro Turbine was developed. • The hydraulic performance of the tail pipe was optimized by orthogonal experiment. • The best blade design can both improve the efficiency of the impeller and reduce hydraulic losses in the outlet passage. • The 4-guide vane of the bell-shaped distributor possesses the best inflow condition for the runner. -- Abstract: Structural simplification and efficient hydraulic performance are key to effectively utilizing ultra-low head water power resources and reducing hydroelectric unit costs. In this study, a computational fluid dynamics (CFD) method was used to predict hydraulic performance of an axial turbine at the Gaoliangjian power station. CFD results agreed well with field test data. Using the same numerical method, a new siphon turbine was then designed based on the original distributor and turbine runner equipment. This study investigated the effect of different siphon outlet passage geometry parameters, runner blade shapes, and distributors on the hydraulic performance of the siphon turbine. The maximum hydraulic efficiency increased to 87.9% under a head of 2.87 m. Finally, the hydraulic performance of the turbine was compared for four different distributor designs after adding an intake sump at the turbine entrance. The bell-shaped distributor with four guide vanes resulted in the highest power output at the lowest head. Therefore, the siphon turbine is a good option for energy conversion in ultra-low water head settings.