Numerical analysis and experimental investigation of wind turbine blades with innovative features: Structural response and characteristics

Innovative features of wind turbine blades with flatback at inboard region, thick airfoils at inboard as well as mid-span region and transversely stepped thickness in spar caps have been proposed by Institute of Engineering Thermophysics, Chinese Academy of Sciences (IET-Wind) in order to improve both aerodynamic and structural efficiency of rotor blades. To verify the proposed design concepts, this study first presented numerical analysis using finite element method to clarify the effect of flatback on local buckling strength of the inboard region. Blade models with various loading cases, inboard configurations, and core materials were comparatively studied. Furthermore, a prototype blade incorporated with innovative features was manufactured and tested under static bending loads to investigate its structural response and characteristics. It was found that rotor blades with flatback exhibited favorable local buckling strength at the inboard region compared with those with conventional sharp trailing edge when low-density PVC foam was used. The prototype blade showed linear behavior under extreme loads in spar caps, aft panels, shear web and flatback near the maximum chord which is usually susceptible to buckling in the blades according to traditional designs. The inboard region of the blade showed exceptional load-carrying capacity as it survived 420% extreme loads in the experiment. Through this study, potential structural advantages by applying proposed structural features to large composite blades of multi-megawatt wind turbines were addressed.