Experimental Tests of a SMA Based Blade Twist System: Wind Tunnel and Whirl Tower Outcomes

Abstract

In this work, attention is paid on two specific moments foreseen in the European Project "Shape Adaptive Blades for Rotorcraft Efficiency": the test validation in wind tunnel and whirl tower representative environments of a morphing architecture aiming at altering the twist law of an helicopter blade. The architecture, based on Shape Memory Alloy technology, was tested in the abovementioned environments to get enough information on its functionality under representative loads and on its capability of producing significant variations of the original performance. The wind tunnel tests held at the University of Bristol, captured the effect of the progressive span wise twist activation, highlighting the capability of improving the aerodynamic efficiency. The whirl tower test campaign organized at the DLR plant, demonstrated the capability of the system of altering its original twist, even in presence of centrifuge forces tending to stretch the blade and, thus, to make it stiffener. In addition, twist related effects were measured, as the produced flapping motion. The achieved results proved, in relevant environment, the effectiveness of the architecture both from a functional (additional twist production) and an effectiveness (alteration of the aerodynamics) point of view. The experimental outcomes paved the way to a critical overview aiming at identifying potential issues and relevant approaches for further increase of the technology readiness level of the concept. Copyright © 2022 by ASME.