Design of an adaptive slat on wind energy rotor blades for wind tunnel investigations

Abstract

To maximize the power output of wind energy plants, their size has been increased to rotor diameters over 120m and nacelle heights of 120m and more. Even with these dimensions, the plants encounter turbulence and vertical wind gradients from the ground boundary layer, which cause fatigue loads on the rotor blades. Minimizing these loads will help to scale up the blades and to enhance their durability. Morphing slats are proposed to minimize these loads. These slats are equipped with an actively controlled morphing trailing edge. To prove the working principle, a wind tunnel model is developed consisting of an aerodynamic profile with rectangular planform (measuring 30 cm chord and 80 cm span) and a morphing slat. In span wise direction 4 actuation stations are used to support and deform the slats trailing edge. The slats trailing edge is connected to a kinematics on each station, consisting of a connecting rod and a shaft. The slat leading edge is fixed at the same span wise position. The intermediate regions of these four positions have gaps between the slat and the main profile, which allow an air flow. Once the shaft starts to turn the compliant middle section of the slat deforms and the gap will be closed and opened while the leading edge stays fixed. This paper deals with the development process of the morphing slat. To ensure the fatigue strength under dynamic deformation the inner contour of the slats middle section will be optimized to reduce the slats strain in deformed state. Also six test slats are manufactured to investigate the strain distribution of the slats skin using an optical image correlation system. Finally the fatigue strength for 1 million oscillations is verified experimentally.