Experimental Investigation on a Mini Hibrid Wind Turbine

The proposed work concerns an experimental investigation of the aerodynamic of a hybrid mini wind turbine which couples the main characteristics of classical mini wind turbine Darrieus and Savonius. The study consisted in the investigation on a prototype of hybrid turbine characterized by a geometry Darrieus with 4 fixed blades and two Savonius blades, positioned internally at the Darrieus, constituted by flexible wings which vary in their extension, reducing the extension at the increase of the angular velocity to wrap completely when the angular speed is such high to allow the wing profiles of Darrieus to generate a positive torque. In order to characterize the hybrid turbine, the flow field was investigated by means of a bidimensional Particle Image Velocimetry (PIV) technique, measuring velocity and vorticity in two aerodynamic configurations (Savonius blades at the maximum extension and at 2/3 of the maximum extension), for two flow conditions, i.e. 5 and 10 m/s, and for two angular velocity of the turbine which correspond at a tangential maximum velocity of 1 and 1.7 m/s. The measurements were performed in a wind tunnel with a measurements test section of approximately 400 x 400 mm and a maximum speed as high as 30 m/s.