A Development of Operating System with Darrieus-type Cross-flow Water Turbine for Ultra-low Head Hydro-power

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The Darrieus-type cross flow water turbine has been developed for ultra low head hydro power from the reason that its simple shape and structure could reduce the capital and maintenance costs. Model tests of the Darrieus-type runner with straight blades in a rectangular ducted casing have been conducted with theoretical consideration to clarify the guiding principles for designing high efficiency runner and operating under optimum control. Results of those systematic works are as follows. 1)Runner blade parameters as the preferable blade sectional profile of NACA0015-0018, the ratio of blade chord length to the radius of pitch circle of the runner of l/R=about0.3, the blade setting angle tangent to the pitch circle are recommended. 2)The compromise between high efficiency and small time variation of torque yeilded three bladed runner. 3)The method to support the blades to the rotating shaft was proposed t o reduce a friction loss of the runner without dete-riorating the blade performance due to a blade tip effect. 4)The characteristics of the self-starting and moving processes of this type of water turbine with a generator and a speed in creasing device to any operating point were evaluated by experiments and a numerical simulation. 5)A simple method to control the system of this type of water turbune effectively was proposed. 6)The curves of hydro performance and cavitation limit of a runner with the optimum configuration were shown as useful data for designing the recommended best efficiency runner. 7)The guiding principles of the optimum wall shapes of the intake, the runner casing and the draft tube were proposed to make the runner performance maximum and all hydraulic losses minimum. And finally 8)the usable range of the Darrieus-type water turbines was illustrated for head and flow capacity with the available output power in comparison with those of other conventional type of water turbines.