Effect of Blade Number on a Straight-Bladed Vertical-Axis Darreius Wind Turbine

TLDR: In this paper, a mean for reducing the torque variation during the revolution of a vertical-axis wind turbine (VAWT) by increasing the blade number is presented, where flow field characteri stics are investigated at several values of tip speed ratio, allowing a quantification of the influence of blade number on flow geometric features and dynamic quantities.

Abstract: This paper presents a mean for reducing the torque variation during the revolution of a vertical-axis wind turbine (VAWT) by increasing the blade number. For this purpose, two- dimensional CDF analysis have been performed on a straight-bladed Darreius-type rotor. After describing the computati onal model, a complete campaign of simulations based on full RANS unsteady calculations is proposed for a three, four and five -bladed rotor architecture characterized by a NACA 0025 airfoil. For each proposed rotor configuration, flow field characteri stics are investigated at several values of tip speed ratio, allowing a quantification of the influence of blade number on flow geometric features and dynamic quantities, such as rotor torq ue and power. Finally, torque and power curves are compared for t he analyzed architectures, achieving a quantification of the ef fect of blade number on overall rotor performance.