Computergestützte Tragflächenoptimierung zur Leistungsverbesserung von Windturbinen mit horizontaler Achse (HAWT) mit einem 3D - Modell

The usage of wind turbines as an alternative source of energy is increasing globally. The improvement of the performance of wind turbines can lower the cost of this type of energy and secure ongoing success. Various aspects can lead to improvements in performance. This study focuses on the computer-aided investigation of aerodynamic performance, which can be improved by optimization of the airfoil shape and its boundary layer. A focus is on the role of the laminar boundary layer on the blade airfoil in improving the aerodynamic performance of the wind turbine. The profile was optimized by means of a Genetic Algorithm (GA). After the optimization, the physical relationship between the laminar boundary layer and three-dimensional rotating augmentation of the wind turbine rotor was found by implementation of the 3D correction code. The Gliding Ratio (GR), transition points, boundary layer thickness, and friction coefficient distributions, which were calculated with the software XFOIL and RFOIL, show that the optimized airfoil has the shape with larger boundary layer and higher GR than the reference profile. The 3D-corrected polar data, calculated by Hansen’s correction law, were used for the calculation of the power production for two different wind turbines. It is to demonstrate that the optimized airfoil shape can influence the wind turbine to produce greatly increased power production. The optimized airfoil gives higher sensitivity on the 3D rotational effect, which makes the optimized one has higher torque and the constant thrust of the blade compared to the reference. The Coriolis force related to the three-dimensional rotation of the rotor generated radial momentum of the blade, which moved the separation bubble towards the tip, while the delayed transition point decreased the separation bubble formation. The optimized airfoil had smaller stall regions and fewer bubble occurrences than the reference airfoil. This is shown in the comparisons of the two-dimensional CFD flow simulation, which was performed with CFD OpenFoam for both airfoils. This study tries to close a knowledge gap in the area of laminar boundary layer considerations of the airfoils of the wind turbine blade. The knowledge gap existed, because the laminar layer in wind turbine and aeronautic applications was considered to be an unimportant and in reality, scarcely-existing region by most researchers and was therefore not emphasized in previous research. Furthermore, the investigations on the physical connection between the airfoil boundary layer and three-dimensional rotating augmentation of wind turbines can serve as a cornerstone for future research on improving the prediction accuracy in the aerodynamic design of wind turbine blades with three-dimensional rotation. The performance improvements of wind turbines given by the slight change of the airfoil curvature can be a great insight for effective aerodynamic improvement in further airfoil research. This airfoil optimization with a laminar boundary layer also demonstrates the connection between the airfoil and the holistic performance improvement of the wind turbine, including aerodynamics and structural stability at the same time