Variable Geometry Chevrons for Jet Noise Reduction

Calkins, Frederick T.; Butler, G. W.; Mabe, James H.

doi:10.2514/6.2006-2546

Cited by 52 publications

(31 citation statements)

References 8 publications

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“…The experimental image was constructed from photogrammetry data. 5 While the system modeled is not strictly identical to that flown, encouraging qualitative agreement is observed.…”

Section: Numerical Analysis Resultsmentioning

confidence: 77%

“…5 The chosen comparison data consists of a contour plot showing the topology of the chevron in the fully heated, fully actuated state, with the reference point (0.0 point) being the location at which the centerline of the chevron is mounted to the fan cowl. These results are shown in Figure 10.…”

Section: Numerical Analysis Resultsmentioning

confidence: 99%

“…Boeing has flight tested one Variable Geometry Chevron (VGC) system which includes active SMA beams encased in a composite structure with a complex 3-D configuration. 4,5 The beams, when activated, induce the necessary bending forces on the chevron structure to deflect it into the flow. Figure 1 illustrates the configuration of these active chevrons prior to flight testing.…”

Section: Introductionmentioning

confidence: 99%

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Characterization and 3-D modeling of Ni60Ti SMA for actuation of a variable geometry jet engine chevron

Hartl

Lagoudas

2007

SPIE Proceedings

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This work describes the thermomechanical characterization and FEA modeling of commercial jet engine chevrons incorporating active Shape Memory Alloy (SMA) beam components. The reduction of community noise at airports generated during aircraft take-off has become a major research goal. Serrated aerodynamic devices along the trailing edge of a jet engine primary and secondary exhaust nozzle, known as chevrons, have been shown to greatly reduce jet noise by encouraging advantageous mixing of the streams. To achieve the noise reduction, the secondary exhaust nozzle chevrons are typically immersed into the fan flow which results in drag, or thrust losses during cruise. SMA materials have been applied to this problem of jet engine noise. Active chevrons, utilizing SMA components, have been developed and tested to create maximum deflection during takeoff and landing while minimizing deflection into the flow during the remainder of flight, increasing efficiency. Boeing has flight tested one Variable Geometry Chevron (VGC) system which includes active SMA beams encased in a composite structure with a complex 3-D configuration. The SMA beams, when activated, induce the necessary bending forces on the chevron structure to deflect it into the fan flow and reduce noise. The SMA composition chosen for the fabrication of these beams is a Ni60Ti40 (wt%) alloy. In order to calibrate the material parameters of the constitutive SMA model, various thermomechanical experiments are performed on trained (stabilized) standard SMA tensile specimens. Primary among these tests are thermal cycles at various constant stress levels. Material properties for the shape memory alloy components are derived from this tensile experimentation. Using this data, a 3-D FEA implementation of a phenomenological SMA model is calibrated and used to analyze the response of the chevron. The primary focus of this work is the full 3-D modeling of the active chevron system behavior by considering the SMA beams as fastened to the elastic chevron structure. Experimental and numerical results are compared. Discussion is focused on actuation properties such as tip deflection and chevron bending profile. The model proves to be an accurate tool for predicting the mechanical response of such a system subject to defined thermal inputs.

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“…The experimental image was constructed from photogrammetry data. 5 While the system modeled is not strictly identical to that flown, encouraging qualitative agreement is observed.…”

Section: Numerical Analysis Resultsmentioning

confidence: 77%

Section: Numerical Analysis Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Characterization and 3-D modeling of Ni60Ti SMA for actuation of a variable geometry jet engine chevron

Hartl

Lagoudas

2007

SPIE Proceedings

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“…Many studies have focused on active flow control by considering the employment of SMAs elements for actuation purposes. Examples of morphing applications regard the improvement of the global efficiency of aircraft wings [3][4][5], noise reduction during aircraft take-off [6], the development of a rotor blade control system [7], the fabrication of actuators for tracking helicopter blades while in-flight [8], and the application of aerodynamic control devices for wind turbine blades [9,10]. The notion of smart advanced blades, which can control themselves and reduce (or eliminate) the need for an active control system, is an appealing solution in blade technology to increase efficiency at several different flow regimes.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Aerodynamic and Structural Performance of a Cooling Fan with Morphing Blade

Suman

Fortini

Aldi

et al. 2017

IJTPP

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Abstract:The concept of smart morphing blades, which can control themselves to reduce or eliminate the need for active control systems, is a highly attractive solution in blade technology. In this paper, an innovative passive control system based on Shape Memory Alloys (SMAs) is proposed. On the basis of previous thermal and shape characterization of a single morphing blade for a heavy-duty automotive cooling axial fan, this study deals with the numerical analysis of the aerodynamic loads acting on the fan. By coupling computational fluid dynamics and finite element method approaches, it is possible to analyze the actual blade shape resulting from both the aerodynamic and centrifugal loads. The numerical results indicate that the polymeric blade structure ensures proper resistance and enables shape variation due to the action of the SMA strips.

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“…On the fourth version of the F-14, the F-14D built in 1991, the glove vanes were removed due to their weight and complexity [1]. Since that time many more sophisticated inflight geometry manipulation systems have been tried and the whole field of "morphing" aircraft" has grown enormously, see for example [2], [3], [4], [5], [6], [7], [8], and [9]. Clearly, morphing geometry must not only improve the aerodynamic capabilities of an aircraft, but also cannot have too severe an impact on cost, weight or energy consumption.…”

Section: Introductionmentioning

confidence: 99%

Analysis and experimental validation of morphing UAV wings

Chanzy¹,

Keane

2017

Aeronaut. j.

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The development of new technologies -such as rapid prototyping -and the use of materials with improved properties -such as highly resistant extruded polystyrene foam which can be easily and precisely shaped, while conserving its mechanical properties -allow researchers to improve design concepts. This paper details the development of a new set of morphing wings for a 15kg maximum take-off weight Unmanned Aerial Vehicle (UAV) from concept design, to flight tests, including modelling, design optimisation, construction and wind tunnel tests. A set of comparator equivalent conventional wings have been used throughout in order to be able to judge any benefits stemming from the adoption of morphing technology. The paper shows that the morphing wings provide a controllable aircraft while reducing drag by a factor of 40% compared to the comparator wings with conventional ailerons in a deflected position. IntroductionMorphing wings have been studied since the earliest days of heavier than air aviation, no doubt based on the commonplace observation that all birds continuously change the shapes of their wings during flight. The original Wright Flyer used "wing warping" for roll control -a fundamental form of wing morphing. There are many and varied ways that the wings of an aircraft can be altered in shape: the planform can be altered in size or span or sweep, section shapes can be altered, either to change lift magnitude and distribution or to gain vehicle control in pitch, roll, yaw, etc., wings can be twisted to alter effective angles of attack. Aeroelastic effects can be deliberately used to make geometry changes -so called aeroelastic tailoring. If allowance is made for the activation and deployment of conventional control surfaces, almost all aircraft lifting surfaces change shape in some way or other. One of the key recent drivers in morphing wing technologies has been the adoption of composite materials such as carbon fibre reinforced plastics. These have allowed for considerable tailoring of stiffness properties throughout the geometry of the wings so as to allow close control of the shape changes being achieved. In the wings developed here a careful matching of fibre and foam structural elements is used to govern the shapes taken up by the wing as it morphs.

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Variable Geometry Chevrons for Jet Noise Reduction

Cited by 52 publications

References 8 publications

Characterization and 3-D modeling of Ni60Ti SMA for actuation of a variable geometry jet engine chevron

Characterization and 3-D modeling of Ni60Ti SMA for actuation of a variable geometry jet engine chevron

Analysis of the Aerodynamic and Structural Performance of a Cooling Fan with Morphing Blade

Analysis and experimental validation of morphing UAV wings

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