Experimental investigation of blade number and design effects for a ducted wind turbine

In this paper, effects of design, number and attack angles of blades on rotational speed are experimentally studied in a duct which increases wind velocity up to 2.46 times numerically and 2.32 times experimentally as great as far-field flow. In order to realize this, 3 different types of aerodynamic blades were designed and then, 2-bladed, 3-bladed and 4-bladed impellers were created by these blades; finally, 9 impellers were built on aggregate. The rotational speed of each impeller was recorded at 7 attack angles in two operating states with and without the duct at the same conditions in a wind tunnel. Results demonstrate that firstly, the rotational speed is reduced by adding more blades; secondly, the impellers with wide top blades have lower rotational speeds; thirdly, the rotational speed is augmented by increasing attack angle from 0 to 75°; therefore, the rotational speed increase ratio is dependent on these 3 parameters and the wind velocity increase ratio at the throat as well.