Selected Applications of Aeropropulsion Actuation and Shape Control Devices Using HTSMAs
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INTRODUCTION
ENABLING a new generation of aircraft engines with reduced noise and more robust performance will require compact, lightweight systems for exhaust nozzle shape adaptation and flow control device deployment. Rapidly maturing smart materials technology can help to enable adaptive control of inlet and exhaust geometry for in-flight optimization of engine flows while minimizing weight and mechanical complexity. This article describes the results of recent activity that built on established device technology using shape memory alloy (SMA) actuators and initiated development of adaptive exhaust nozzle concepts suitable for application to nextgeneration jet transports. A critical element of this work entailed leveraging new developments in high-temperature SMA (HTSMA) materials to implement test articles that illustrated the feasibility of developing HTSMA actuators for use in flight. This work featured mutually supporting design, analysis, and test activities, including extension of the database on Pt-, Pd-, and Hf-doped NiTi HTSMA materials for propulsion applications; construction and test of a benchtop adaptive nozzle component demonstrator using HTSMAs; and wind tunnel testing of a model scale HTSMA-driven nozzle element in high-speed flow with loads representative of subsonic flight. A full description of these activities is given in Reference 1; this article focuses on the benchtop and wind tunnel testing reported in that document. Additionally, however, assessment of the effectiveness of the HTSMA material developed and supplied for
TODD QUACKENBUSH and ROBERT MCKILLIP, Jr., Senior Associates, are with Continuum Dynamics, Inc., Ewing, NJ 08618. Contact e-mail: [email protected] Manuscript submitted March 31, 2011. Article published online December 1, 2011 2870—VOLUME 43A, AUGUST 2012
support of this work by investigators at NASA/Glenn Research Center is outlined.
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MOTIVATION AND BACKGROUND
Noise mitigation for subsonic transport aircraft is a continuing high priority, given the strong role played by aircraft noise characteristics in community acceptance.[2,3] Recent work[4–7] has identified successful mixing enhancement devices for engine exhaust flows—most notably, chevrons—that have demonstrated a substantial capability for reducing aircraft noise (Figure 1). However, current fixed-geometry chevrons impose a small but significant performance penalty on aircraft engines[5,8] and are necessarily constrained to minimizing engine noise over a limited range of flight conditions. Adaptive chevrons can be developed by exploiting rapidly maturing SMA technology. Such a variable geometry capability would allow for the reconfiguration of chevrons to maximize noise mitigation in crucial takeoff and landing modes while minimizing the drag/performance penalties during cruise. By exploiting new-generation, high-temperature SMA materials technology, it is anticipated that these devices will operate in both low-temperature (fan) and high-temperature (core) exhaust flows. The potential of exhaust mixing strategi
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