The Experts below are selected from a list of 3900 Experts worldwide ranked by ideXlab platform
Dimitri Papamoschou - One of the best experts on this subject based on the ideXlab platform.
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aeroacoustics of three stream high speed jets from coaxial and asymmetric nozzles
51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2013Co-Authors: Dimitri Papamoschou, Andrew Johnson, Vincent PhongAbstract:The development of three-stream variable cycle Turbofan Engines provides an opportunity for noise reduction by optimizing the exhaust conditions of the secondary and tertiary streams. This includes adjustment of the velocity ratios and, more importantly, reshaping of the nozzle. The paper reviews an experimental study of subscale three-stream nozzles, rapid-prototyped with high accuracy and operating at high specific thrust. Far-field noise surveys were collected using a 24-microphone array. For low-bypass configurations, applicable to supersonic aircraft, a coaxial configuration offers no significant noise benefit compared to the single-stream exhaust. Configurations with offset secondary or tertiary streams offer significant noise reduction in the direction of the thicker flow. For bypass ratio around 0.5, reductions of 5.1 dB in overall sound pressure level and 4.2 dB in effective perceived noise level were attained.
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optimization of fan flow deflection for supersonic Turbofan Engines
AIAA CEAS Aeroacoustics Conference, 2008Co-Authors: Preben E Nielsen, Dimitri PapamoschouAbstract:*† This study involves the application of fan flow deflectors for suppression of jet noise from low-bypass Turbofan Engines for next-generation supersonic aircraft. Experiments using canonical vane deflectors seek to establish correlations between aerodynamics, distortion of the mean velocity field in the jet plume, and noise reduction. The maximum radial velocity gradient, as a function of axial distance and azimuth angle, is used to quantify distortions of the plume. Vanes mounted at low azimuth angles (with respect to the downward vertical) reduce gradients in the downward direction, while vanes mounted at high azimuth angles reduce gradients in the sideline reduction. There is a significant correlation between gradient reduction and noise suppression in the azimuthal direction of the gradient. In addition, it is found that vanes with cambered airfoils perform better than vanes with symmetric airfoils. The trends obtained were used in the successful design of deflector configurations consisting of two pairs of vanes which resulted in cumulative peak overall sound pressure level (OASPL) and effective perceived noise level (EPNL) reductions of 8.8 dB and 6.7 dB respectively.
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fan flow deflection for supersonic Turbofan Engines
46th AIAA Aerospace Sciences Meeting and Exhibit, 2008Co-Authors: Dimitri Papamoschou, Preben E NielsenAbstract:We present an initial parametric investigation of fan flow deflectors for suppressing noise from supersonic Turbofan Engines. Realistic exhaust geometry and flow conditions for bypass ratio 2.7 were simulated in a subscale experiment. The study encompassed acoustic measurement and mean velocity surveys. The deflectors comprised internal vanes with both symmetric and cambered airfoil sections and deployable external flaps. Superior acoustic results were achieved using a combination of cambered vanes and perforated flaps, yielding cumulative (downward plus sideline) EPNL and OASPL reductions of 7.7 dB and 9.2 dB respectively. A fair correlation is established between the suppression of peak OASPL and the reduction of the radial velocity gradient on the underside of the jet.
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acoustic simulation of coaxial hot air jets using cold helium air mixture jets
Journal of Propulsion and Power, 2007Co-Authors: Dimitri PapamoschouAbstract:This work examines the ability of small-scale helium-air mixture coaxial jets to simulate the acoustics of large-scale hot air jets representing the exhaust of separate-flow Turbofan Engines. Experiments employed a one-eighth-scale model of a separate-flow nozzle used in hot tests at NASA John H. Glenn Research Center. Comparisons were conducted for two set points using the following methods: matching velocity and density, and matching velocity and Mach number. For both methods, the helium-air data compare well with the hot data in all measures of noise: spectral shapes, spectral levels, and overall sound pressure levels. The method of matching velocity and Mach number gives slightly better agreement in the spectral shapes at angles close to the jet axis and in the overall sound pressure levels. The overall agreement between the hot air and helium-air mixture data is within 1.2 dB.
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fan flow deflection in simulated Turbofan exhaust
AIAA Aerospace Sciences Meeting and Exhibit, 2006Co-Authors: Dimitri PapamoschouAbstract:Fan flow deflection for jet noise reduction was applied to subscale nozzles simulating the geometry and exhaust conditions of separate-flow Turbofan Engines. Two types of deflectors were tested, one comprising two pairs of vanes internal to the fan duct and the other consisting of a wedge positioned outside the fan duct. The noise reduction achieved by the vanes was strong in the downward direction and moderate in the sideline direction. The wedge generated significant attenuation in both directions. The acoustic results are consistent with the measured distortion of the mean velocity field. An approach for the treatment ofnonaxisymmetricjets vis-a-vis perceived noise prediction is introduced.
Russell H Thomas - One of the best experts on this subject based on the ideXlab platform.
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system noise assessment of blended wing body aircraft with open rotor propulsion
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Yueping Guo, Russell H ThomasAbstract:An aircraft system noise study is presented for the hybrid wing–body aircraft concept with open-rotor Engines mounted on the upper surface of the airframe. The aircraft chosen for the study is of a size comparable to the Boeing 787 aircraft. It is shown that, for such a hybrid wing–body aircraft, the cumulative effective perceived noise level is about 24 dB below the current aircraft noise regulations of stage 4. Although this makes the design acoustically viable in meeting the regulatory requirements, even with the consideration of more stringent noise regulations in the next decade or so, the design will likely meet stiff competition from aircraft with Turbofan Engines. The noise levels of the hybrid wing–body design are held up by the inherently high noise levels of the open-rotor Engines and the limitation on the shielding benefit due to the practical design constraint on the engine location. Furthermore, it is shown that the hybrid wing–body design has high levels of noise from the main landing gear,...
Yueping Guo - One of the best experts on this subject based on the ideXlab platform.
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system noise assessment of blended wing body aircraft with open rotor propulsion
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Yueping Guo, Russell H ThomasAbstract:An aircraft system noise study is presented for the hybrid wing–body aircraft concept with open-rotor Engines mounted on the upper surface of the airframe. The aircraft chosen for the study is of a size comparable to the Boeing 787 aircraft. It is shown that, for such a hybrid wing–body aircraft, the cumulative effective perceived noise level is about 24 dB below the current aircraft noise regulations of stage 4. Although this makes the design acoustically viable in meeting the regulatory requirements, even with the consideration of more stringent noise regulations in the next decade or so, the design will likely meet stiff competition from aircraft with Turbofan Engines. The noise levels of the hybrid wing–body design are held up by the inherently high noise levels of the open-rotor Engines and the limitation on the shielding benefit due to the practical design constraint on the engine location. Furthermore, it is shown that the hybrid wing–body design has high levels of noise from the main landing gear,...
R Logan - One of the best experts on this subject based on the ideXlab platform.
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chemical characterization of the fine particle emissions from commercial aircraft Engines during the aircraft particle emissions experiment apex 1 to 3
Environmental Science & Technology, 2011Co-Authors: John S Kinsey, Yuanji Dong, M D Hays, D C Williams, R LoganAbstract:This paper addresses the need for detailed chemical information on the fine particulate matter (PM) generated by commercial aviation Engines. The exhaust plumes of seven Turbofan engine models were sampled as part of the three test campaigns of the Aircraft Particle Emissions eXperiment (APEX). In these experiments, continuous measurements of black carbon (BC) and particle surface-bound polycyclic aromatic compounds (PAHs) were conducted. In addition, time-integrated sampling was performed for bulk elemental composition, water-soluble ions, organic and elemental carbon (OC and EC), and trace semivolatile organic compounds (SVOCs). The continuous BC and PAH monitoring showed a characteristic U-shaped curve of the emission index (EI or mass of pollutant/mass of fuel burned) vs fuel flow for the Turbofan Engines tested. The time-integrated EIs for both elemental composition and water-soluble ions were heavily dominated by sulfur and SO42-, respectively, with a ∼2.4% median conversion of fuel S(IV) to particl...
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physical characterization of the fine particle emissions from commercial aircraft Engines during the aircraft particle emissions experiment apex 1 3
Atmospheric Environment, 2010Co-Authors: John S Kinsey, Yuanji Dong, Craig D Williams, R LoganAbstract:Abstract The fine particulate matter (PM) emissions from nine commercial aircraft engine models were determined by plume sampling during the three field campaigns of the Aircraft Particle Emissions Experiment (APEX). Ground-based measurements were made primarily at 30 m behind the engine for PM mass and number concentration, particle size distribution, and total volatile matter using both time-integrated and continuous sampling techniques. The experimental results showed a PM mass emission index (EI) ranging from 10 to 550 mg kg −1 fuel depending on engine type and test parameters as well as a characteristic U-shaped curve of the mass EI with increasing fuel flow for the Turbofan Engines tested. Also, the Teflon filter sampling indicated that ∼40–80% of the total PM mass on a test-average basis was comprised of volatile matter (sulfur and organics) for most Engines sampled. The number EIs, on the other hand, varied from ∼10 15 to 10 17 particles kg −1 fuel with the Turbofan Engines exhibiting a logarithmic decay with increasing fuel flow. Finally, the particle size distributions of the emissions exhibited a single primary mode that were lognormally distributed with a minor accumulation mode also observed at higher powers for all Engines tested. The geometric (number) mean particle diameter ranged from 9.4 to 37 nm and the geometric standard deviation ranged from 1.3 to 2.3 depending on engine type, fuel flow, and test conditions.
Preben E Nielsen - One of the best experts on this subject based on the ideXlab platform.
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optimization of fan flow deflection for supersonic Turbofan Engines
AIAA CEAS Aeroacoustics Conference, 2008Co-Authors: Preben E Nielsen, Dimitri PapamoschouAbstract:*† This study involves the application of fan flow deflectors for suppression of jet noise from low-bypass Turbofan Engines for next-generation supersonic aircraft. Experiments using canonical vane deflectors seek to establish correlations between aerodynamics, distortion of the mean velocity field in the jet plume, and noise reduction. The maximum radial velocity gradient, as a function of axial distance and azimuth angle, is used to quantify distortions of the plume. Vanes mounted at low azimuth angles (with respect to the downward vertical) reduce gradients in the downward direction, while vanes mounted at high azimuth angles reduce gradients in the sideline reduction. There is a significant correlation between gradient reduction and noise suppression in the azimuthal direction of the gradient. In addition, it is found that vanes with cambered airfoils perform better than vanes with symmetric airfoils. The trends obtained were used in the successful design of deflector configurations consisting of two pairs of vanes which resulted in cumulative peak overall sound pressure level (OASPL) and effective perceived noise level (EPNL) reductions of 8.8 dB and 6.7 dB respectively.
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fan flow deflection for supersonic Turbofan Engines
46th AIAA Aerospace Sciences Meeting and Exhibit, 2008Co-Authors: Dimitri Papamoschou, Preben E NielsenAbstract:We present an initial parametric investigation of fan flow deflectors for suppressing noise from supersonic Turbofan Engines. Realistic exhaust geometry and flow conditions for bypass ratio 2.7 were simulated in a subscale experiment. The study encompassed acoustic measurement and mean velocity surveys. The deflectors comprised internal vanes with both symmetric and cambered airfoil sections and deployable external flaps. Superior acoustic results were achieved using a combination of cambered vanes and perforated flaps, yielding cumulative (downward plus sideline) EPNL and OASPL reductions of 7.7 dB and 9.2 dB respectively. A fair correlation is established between the suppression of peak OASPL and the reduction of the radial velocity gradient on the underside of the jet.
