Cross-Flow Turbine Design For Energy Production And Discharge Regulation

Cross-flow turbines are very efficient and cheap turbines that allow a very good cost/benefit ratio for energy production located at the end of conduits carrying water from a water source to a tank. In this paper a new design procedure for a cross-flow turbine working with a variable flow rate is proposed. The regulation of the head immediately upstream the turbine is faced by adopting a shaped semicircular segment moving around the impeller. The maximum efficiency of the turbine is attained by setting the velocity of the particles entering the impeller at about twice the velocity of the rotating system at the impeller inlet. If energy losses along the pipe are negligible, the semicircular segment allows always a constant hydraulic head and a constant velocity at the impeller inlet, even with variable flow rate. The decrease of the turbine efficiency along with the inlet surface reduction is first investigated; a design methodology, using also CFD simulations, is then proposed for both the cases of negligible and not negligible energy losses along the pipe.