Experimental Studies on a Preferable Blade Profile for High Efficiency and the Blade Characteristics of Darrieus-Type Cross-Flow Water Turbines

Abstract

Fluid forces and moment acting on a blade of a Darrieus-type runner were measured in addition to the blade performance. The characteristics for various type of blades were evaluated from the measured data with theoretical considerations in an inviscid flow. Some features of those characteristics, including the dynamic effects caused by an unsteady relative flow around the Darrieus blade, are shown in the present paper. For high efficiency, a noncambered thin blade with relatively long chord length is recommended. Its characteristics are high lift slope, high lift at zero angle of attack and relatively low drag in a wide no-stall region of attack angles. It should also be set tangent to the runner pitch-circle at the 50% chord point of the blade.