Testing of SMA-enabled active chevron prototypes under representative flow conditions

Abstract

Control of jet noise continues to be an important research topic. Exhaust-nozzle chevrons have been shown to reduce jet noise, but parametric effects are not well understood. Additionally, thrust loss due to chevrons at cruise suggests significant benefit from active chevrons. The focus of this study is development of an active chevron concept for the primary purpose of parametric studies for jet noise reduction in the laboratory and secondarily for technology development to leverage for full scale systems. The active chevron concept employed in this work consists of a laminated composite structure with embedded shape memory alloy (SMA) actuators, termed a SMA hybrid composite (SMAHC). SMA actuators are embedded on one side of the neutral axis of the structure such that thermal excitation, via joule heating, generates a moment and deflects the structure. The performance of two active chevron concepts is demonstrated in the presence of representative flow conditions. One of the concepts is shown to possess significant advantages for the proposed application and is selected for further development. Fabrication and design changes are described and shown to produce a chevron prototype that meets the performance objectives.

Analysis, optimization and testing of morphing structures employing shape memory alloy actuators

“…The most notable variation refers to the initial chevron position near tip, under the various flow conditions considered in this test series. In a later work of Turner et al (2008) the circumferential radius of curvature was considered as well as the design of two chevrons with different actuators schemes (Turner et al, 2007). Subsequently two representative prototypes were fabricated and tested under adequate flow conditions to down-select the final configuration and refine the design to meet the performance objectives under flow.…”

Thermomechanically coupled analysis and experimental investigation of morphing structures with shape memory alloy actuators operating under partial transformation with a focus on active load control

“…Both prototypes presented repeatable performance as well as permanent deformation that was accumulated with thermal cycles. Further testing of the concepts under the presence of representative flow conditions [99] revealed significant advantages to facilitate the selection between them. Finally, fabrication and design changes were described for the development of a chevron according to predefined performance criteria.…”