Aerodynamic Performance of Morphing Blades and Rotor Systems

This paper introduces the Shape Adaptive Blades for Rotorcraft Efficiency (SABRE) Horizon 2020 research program and presents initial comprehensive analysis results on the efficacy of adapting blade shapes as a means of reducing rotorcraft power requirements and emissions. The aims of the research program are introduced, followed by discussion of the six different morphing concepts that will be explored. The morphing mechanisms are based on active camber, chord extension, twist, and active tendon morphing technologies. SABRE will explore the use of these concepts individually and in combination, for rotor quasi-steady configuration-type morphing and up to 2/rev actuation of some of the mechanisms, with the objective being to find the best balance between emissions reductions versus complexity and added weight. Initial investigations into the potential power reductions compared to the baseline full-scale BO-105 main rotor achievable with the morphing concepts were performed using Blade Element Momentum Theory and a comprehensive analysis model that was developed using CAMRAD II. The analytical model was validated by full-scale rotor wind tunnel measurements. A combination of active twist and active chord extension achieved up to 11% performance gain in hover. Active camber morphing performance was very sensitive to the combination of deflection, morphing section radial length and placement on the blade, as well as the actuation phasing and blade loading coefficient. The active camber morphing showed power reductions of up to 5.5% in hover and 5% at an advance ratio of 0.313 with a 2/rev actuation, while the active tendon concept showed the capability to change the dynamic response of the rotor blade.