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A ducted Darrieus-type turbine has been proposed for hydropower utilization of extra-low head less than 2 m.Though the hydro turbine system,in general,might consist of an intake,runner casing section and a draft tube for higher efficiency operation,it was clarified in previous experiment that there was no need of the side-walls of runner casing section and a draft-tube for keeping the efficiency high in the case of duct with an inlet nozzle.This would yield a simplification of the structure of the turbine system.In order to reconfirm this result for large-sized turbine with 560 mm×300 mm duct,instead of small-sized one with 400 mm×200 mm duct,the side-wall effect on turbine performance was experimentally investigated for three-or four-bladed runner.In the present paper,the experimental results are shown with considering flow behaviors in the runner section.
A ducted Darrieus-type turbine has been proposed for hydropower utilization of extra-low head less than 2 m. Hough the hydro turbine system, in general, might consist of an intake, runner casing section and a draft tube for higher efficiency operation, it was clarified in previous experiment that there was no need of the side-walls of runner casing section and a draft-tube for keeping the efficiency high in the case of duct with an inlet nozzle. This would yield a simplification of the structure of the turbine system.In order to reconfirm this result for large-sized turbine with 560 mm × 300 mm duct, instead of small-sized one with 400 mm × 200 mm duct, the side-wall effect on turbine performance was experimentally investigated for three-or four-bladed runner. In the present paper, the experimental results are shown with considering flow behaviors in the runner section.