Abstract
Two new type turbines which alternately combined flat blade with pitched blade were invented. They were a DOWN-impeller with down-flow-type pitched blades and an UP-impeller with up-flow-type pitched blades. The behavior of cavities and the mechanism of power transfer for the new type turbines were investigated by measuring the pressure distribution on the blade surface, and the effect on adjacent blades was clarified by comparing them for a paddle, a down-flow pitched blade turbine and an up-flow pitched blades turbine. Power per blade due to form drag was calculated from the pressure difference between the front and back side of a blade. Power transferred from blade to liquid for both flat and pitched blade of the new type turbines was greater than that for conventional turbines operating under the same conditions. It was found that the cavity behavior of new type turbines was very different from that of conventional turbines, and the reduction of power consumption due to aeration for the new type turbines was less than that for conventional turbines. The reduction of power consumption in a gassed condition was controlled with the form drag.
