On the Effectiveness of Retrofitted Airfoil Leading Edge Devices to Limit Lift

Abstract

Horizontal Axis Wind Turbines are operated with different safety mechanisms which protect the wind turbines from overloading during strong wind situations. However, wind turbines may collapse due to sudden gust events or other overload situations. An additional safety measure may be an aerodynamic load limit of the airfoils themselves by adding passive lift limiting devices to the wing. Ideally, these devices would not add extra drag and the aerodynamic performance will maintain in the normal operation range of the wings. The investigated small radii or ‘noses’ added to the leading edge of a laminar airfoil shows very promising results: the lift limit can be adjusted by the shape, position and spanwise distribution of the added ‘nose’. Additional drag can be kept to a minimum within a certain operation range of the airfoil, depending on the geometrical characteristics of the added nose.