Optimization of Fan Flow Deflection for Supersonic Turbofan Engines

Nielsen, Preben E.; Papamoschou, Dimitri

doi:10.2514/6.2008-3061

Cited by 5 publications

(6 citation statements)

References 9 publications

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“…Past work has focused on correlating the overall sound pressure level (OASPL) with the mean velocity gradient 4 . The rationale was that the rate of production of turbulent kinetic energy (TKE) is driven by the velocity gradient, therefore reductions in the gradient should result in less TKE and thus less potential for noise emission in the direction of the reduced gradients.…”

Section: Introductionmentioning

confidence: 99%

“…The connection between TKE and sound generation is evident in acousticanalogy models used for noise prediction 5 . Tentative correlations were obtained between the reduction in OASPL and the reduction of the velocity gradient near the end of the primary potential core 4 . That study did not examine the effects of the inflectional layers of the jet, to be defined below, that occur in the vicinity of the jet exit.…”

Section: Introductionmentioning

confidence: 99%

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Mean Flow - Acoustic Correlations for Dual-Stream Asymmetric Jets

Nielsen

Papamoschou

2009

47th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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We present an experimental study, comprising acoustic and mean-flow measurements, of several fan-flow deflector configurations in a subscale dual-stream supersonic turbofan nozzle. The deflectors encompassed internal vanes and external wedges. The aim of the study was to investigate trends of high-frequency noise reduction, in the direction of peak emission, versus the distortion of the velocity field in the jet plume. The distortion is quantified in terms of the volume of the inflectional region of the jet, in a particular azimuthal direction, normalized by the volume of the high-speed region of the jet. It is observed that fan flow deflection generally increases the volume of the inflectional region (in the downward and sideline azimuthal directions) and decreases the volume of the high-speed region. Correlations of sound pressure level with the volume-ratio parameter show rapid noise suppression for small values of the volume ratio followed by slower noise reduction at higher values. The correlations appear to validate the hypothesized physics of noise suppression by an enlarged secondary core, and provide practical guidance for the implementation of the fan flow deflection method Nomenclature

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mean Flow - Acoustic Correlations for Dual-Stream Asymmetric Jets

Nielsen

Papamoschou

2009

47th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…The azimuthal mounting positions are the same as those for the first 3 4-V cases. Because the airfoil is cambered, a smaller angle of attack (4 • ) is set for this configuration. Despite the small angle of attack, both the Mach contours and the surface pressure distribution show a large supersonic pocket with a strong terminating shock wave on the back of the airfoil.…”

Section: Iiib Flow Field Around the Deflector Vanesmentioning

confidence: 99%

Computation of the Flow of a Dual-Stream Jet With Fan Flow Deflectors for Noise Reduction

Xiong

Liu

Papamoschou

2009

39th AIAA Fluid Dynamics Conference

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This paper studies the impact of installing noise-suppressing deflector vanes in the bypass flow on the aerodynamic performance of the dual-stream supersonic nozzle of a turbofan engine by using a three-dimensional Reynolds-averaged Navier-Stokes computer program. A series of nozzle configurations using a single pair or double pairs of vanes with NACA0012, NACA4412, and NACA7514 airfoil profiles are investigated. The effects of the azimuthal mounting position of the deflector vanes, angle of attack, and shape of the airfoils are studied. The flow field around the vanes, overall flow turning angle, reduction of turbulent kinetic energy, thrust loss, and blockage caused by the deflector vanes are examined. Recommendations regarding the choice of airfoil and mounting configurations are made for best noise suppressing effectiveness with minimum loss of thrust and mass flow.

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“…3 Graduate Researcher, Department of Mechanical and Aerospace Engineering, srostami@uci.edu, AIAA Student Member. 4 Professor, Department of Mechanical and Aerospace Engineering, fliu@uci.edu, AIAA Associate Fellow. 5 Professor, Department of Mechanical and Aerospace Engineering, dpapamos@uci.edu, AIAA Fellow.…”

mentioning

confidence: 99%

“…Past experiments utilized vanes with standard airfoil sections (NACA0012, NACA4412 and NACA7514). 4 These airfoils were designed for constant freestream environments, while the FFD vane airfoils are immersed in an externally-imposed favorable pressure gradient (accelerating freestream) due to the convergence of the fan duct. Computations of the flow field inside the fan nozzle revealed that the symmetric NACA0012 airfoil has a tendency of generating excessive suction near the leading edge, while the cambered NACA4412 and NACA7514 airfoils produce a large supersonic pocket over the airfoil resulting in the formation of a strong shock wave.…”

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confidence: 99%

Aerodynamic and Acoustic Optimization for Fan Flow Deflection

Johnson

Xiong

Rostamimonjezi

et al. 2011

49th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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This investigation seeks to optimize the implementation of fan flow deflection for jet noise suppression from a supersonic turbofan nozzle with bypass ratio 2.7. The design objective is to maximize reduction of noise perceived by the community while minimizing aerodynamic losses. An adjoint method for shape optimization is used to obtain deflector vane designs with sufficient flow deflection and minimum thrust penalty. A NACA0012 airfoil is used as the initial shape for the vane airfoil. Optimization leads to reduction in specific-thrust loss and a thicker airfoil which is beneficial for structural reasons. The optimal vane airfoil is used in a parametric acoustic study of 50 deflector configurations with variable vane chord length, angle of attack and azimuth angle. The best configuration leads to reductions in effective perceived noise level (EPNL) of 2.8 dB in the downward direction and 2.5 dB in the sideline direction. Addition of a porous wedge-shaped fan flow deflector increases the EPNL reductions to 5.0 dB and 3.9 dB in the downward and sideline directions, respectively.

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Optimization of Fan Flow Deflection for Supersonic Turbofan Engines

Cited by 5 publications

References 9 publications

Mean Flow - Acoustic Correlations for Dual-Stream Asymmetric Jets

Mean Flow - Acoustic Correlations for Dual-Stream Asymmetric Jets

Computation of the Flow of a Dual-Stream Jet With Fan Flow Deflectors for Noise Reduction

Aerodynamic and Acoustic Optimization for Fan Flow Deflection

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