Mean Flow and Noise Prediction for a Separate Flow Jet with Chevron Mixers

Koch, L. Danielle; Bridges, Jackie; Khavaran, Abbas

doi:10.2514/6.2004-189

Cited by 19 publications

(10 citation statements)

References 7 publications

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“…The presence of chevrons on a nozzle produces a scalloped (serrated) trailing edge with the chevrons protruding into the flow, increasingly from root to tip, in the flow direction. All model-scale noise reduction and/or flow studies involving chevrons have been performed using static chevron technology, where the geometry and resulting flow immersion is predetermined and invariant [2][3][4][5][6][7][8][9][10][11][12] . These studies typically included some parametric investigation of chevron number, geometry, and degree of immersion.…”

Section: Introductionmentioning

confidence: 99%

Development of a SMA hybrid composite jet engine chevron concept

et al. 2007

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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 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 bending axis of the structure such that thermal excitation generates a moment and deflects the structure. Two active chevron concepts are demonstrated; one that is powered to immerse and one that is powered to retract. A brief description of the chevron designs is followed by details of the fabrication approach. Results from bench-top tests are presented and correlated with predictions from a numerical model. Very repeatable performance is achieved with excellent agreement between predicted and measured results. Although the deflection requirement is not achieved in the presented results, the approach to meeting the performance requirement is evident.

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Section: Introductionmentioning

confidence: 99%

Development of a SMA hybrid composite jet engine chevron concept

et al. 2007

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“…Chevrons produce a scalloped or serrated trailing edge to a jet exhaust nozzle and protrude into the exhaust flow. All model-scale noise reduction and/or flow studies involving chevrons have been performed using static chevron technology, in which the geometry and resulting flow immersion are predetermined and invariant [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. These studies typically included some parametric investigation of chevron number, geometry, and/or immersion.…”

mentioning

confidence: 99%

Development of a Preliminary Model-Scale Adaptive Jet Engine Chevron

et al. 2008

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Reduction of jet noise continues to be an important research topic. Exhaust-nozzle chevrons have been shown to reduce jet noise, but parametric effects, including immersion amount and azimuthal distribution, are not well understood. Additionally, thrust loss due to static chevrons at cruise suggests a significant benefit from deployable chevrons. The focus of this study is the development of an adaptive-chevron concept for the primary purpose of parametric studies for jet noise reduction in the laboratory and secondarily for development of technology that can be leveraged for full-scale systems. The adaptive-chevron concept employed in this work consists of a laminated composite structure with embedded shape memory alloy actuators. The actuators are embedded on one side of the middle surface such that joule heating of the actuators causes them to attempt recovery of prestrain, thereby generating a moment and deflecting the structure. A brief description of the chevron design is given followed by details of the fabrication approach. Results from bench-top tests are presented and correlated with numerical predictions from a model for such structures that was previously implemented in MSC.Nastran and ABAQUS. Excellent performance and agreement with predictions is demonstrated. Results from tests in a representative flow environment are also presented. Excellent performance is again achieved for both open-and closed-loop tests, the latter demonstrating control of deflection to a specified immersion into the flow. The actuation authority and immersion performance is shown to be relatively insensitive to nozzle pressure ratio. Very repeatable immersion control with modest power requirements is demonstrated. Nomenclature A = austenitic transformation temperature E = Young's modulus G = shear modulus M = martensitic transformation temperature or Mach number P = pressure T = temperature v = volume fraction V = velocity = coefficient of thermal expansion " = normal strain = Poisson's ratio = normal stress Subscripts a = actuator (shape memory alloy) aw= adiabatic wall f = finish ideal = ideal gas m = matrix material r = recovery stress (shape memory alloy) s = start t = total 1 = orthotropic principal material coordinate 1 2 = orthotropic principal material coordinate 2 12 = 1-2 plane of an orthotropic material

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“…In the past, this was accomplished using lobed mixer nozzles. More recently, the addition of chevrons [1][2][3][4][5][6][7][8][9] has been examined and found to reduce noise by up to 2.5 EPNdB during installed testing. However, while nozzles with chevrons can significantly reduce low frequency noise, they do so at the expense of increasing high frequency noise.…”

Section: Introductionmentioning

confidence: 99%

Computational Analyses of Offset Stream Nozzles for Noise Reduction

Dippold

Foster

Wiese

2007

13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference)

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The Wind computational fluid dynamics code was used to perform a series of simulations on two offset stream nozzle concepts for jet noise reduction. The first concept used an S-duct to direct the secondary stream to the lower side of the nozzle. = nozzle plenum total temperature u = local axial velocity ujet = mass-averaged axial velocity of primary jet x, y, z = coordinate system ( ) = used to denote difference in discharge or thrust coefficient of the current configuration from the baseline configuration

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Mean Flow and Noise Prediction for a Separate Flow Jet with Chevron Mixers

Cited by 19 publications

References 7 publications

Development of a SMA hybrid composite jet engine chevron concept

Development of a SMA hybrid composite jet engine chevron concept

Development of a Preliminary Model-Scale Adaptive Jet Engine Chevron

Computational Analyses of Offset Stream Nozzles for Noise Reduction

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