Experimental investigation of a flexible trailing edge for wind energy blades

Abstract

In the last decades the dimensions of wind energy turbines have increased to allow higher power output. This results in a higher loading of the blades due to their own weight. Especially cyclic bending moments at the blade root caused by the weight of the blade, wind shear and gust loads are limiting the blades lifetime at larger scales. Lowering these loads could allow larger blades, a longer lifetime or a lighter construction. Load reduction can be achieved by using a trailing edge flap at the outer region of the blade, comparable to an aircraft rudder, which is capable of moving several times per blade revolution. In contrast to aircraft, sealing against environmental media, such as rain, dust, insects and so on is much more important to allow a high lifetime. Therefore, a flexible and gapless trailing edge has been designed within the SmartBlades project for the mentioned purpose. In the presentation, an overview will be given about the concept and the design process including finite-element-modelling and a basic aerodynamic model. As a result of this, a prototype has been built, which is suited to be tested at a rotating test rig. It comprises a variety of measurement sensors, such as pressure taps, accelerometers and strain gauges in the trailing edge. The rotation tests were performed in collaboration with the Danish Technical University in 2018 on a 10 m radius boom. This boom was rotated at 20/min at several pitch angles. The presentation will close with a set of measurement results obtained from the rotating test. There, an influence on the flow conditions can be shown.