Design and Simulation of Active External Trailing-Edge Flaps for Wind Turbine Blades on Load Reduction

Abstract

A smart material–based active external trailing-edge flap was designed for wind turbine blades in this study. Its vibration-fatigue load reduction potential was evaluated during normal operation. The blade–external flap configuration was chosen based on a wind tunnel–testing report of the National Advisory Committee for Aeronautics. The internal structure of the flap was determined based on an aeroelastic sectional analysis code, with the input of aerodynamic forces obtained from a computational fluid dynamics simulation in order to meet strength and serviceability requirements. The work done by the aerodynamic forces and centrifugal forces acting on the flap was calculated to determine the required actuator capacity. Piezoelectric stack actuators combined with a double-lever mechanical linkage were designed to achieve the required force and displacement in order to activate the flap. By combining the flap control scheme and the aerodynamic-aeroelastic simulation, the time responses of the wind turbine blades were obtained. The fatigue analysis showed that the external flap can reduce the fluctuation of the blade root flapwise bending moment and the magnitude of the damage equivalent loads.