Experimental investigation of multielement airfoils for large-scale wind turbines

Abstract

Experimental results for high-lift multielement airfoils for application to megawatt-scale wind turbines are presented in this thesis. Two different airfoil configurations tested were designed for the inboard section of a 10 MW-scale wind turbine. The airfoil systems were designed as an airfoil system to replace a baseline airfoil that is 40.1% thick. A three-element system consisted of a main element and two flaps and a four-element system was tested with an additional strut. Experiments were performed with the ability to move two flaps to any location relative to a main element. Data were collected at a constant Reynolds number of 1.0 million. Tests were performed in the University of Illinois low turbulence subsonic wind tunnel with a chord length of approximately 1.5 feet (0.46 m) and a model span of approximately 2.8 feet (0.85 m). Results for the Reynolds number tested indicate that lift and drag do not always follow the same trends with respect to gap or overhang. In general, gap size should be no smaller than 2.0% system chord to avoid degradation in performance. In addition, a large overhang can adversely affect aerodynamic performance and lead to a loss of lift but also a reduction in drag. Consequently, it is important in the airfoil design process to identify the balance between aerodynamic efficiency and high lift configurations.