Jet Noise Shielding Provided by a Hybrid Wing Body Aircraft

Doty, Michael J.; Brooks, Thomas F.; Burley, Casey L.; Bahr, Christopher J.; Pope, D. Stuart

doi:10.2514/6.2014-2625

Cited by 26 publications

(17 citation statements)

References 19 publications

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“…As mentioned earlier, data presented in this section were obtained from test cases simulating an approach flight condition. Assuming the shielding benefits for the tonal component of turbomachinery noise to be the same as that measured for the broadband component, the effect of engine placement on the EPNL was estimated 7 . The results are plotted in Figure 12.…”

Section: Effect Of Engine Location On Noise Shieldingmentioning

confidence: 99%

“…Multi-positional jet engines and broadband engine noise simulators were also developed by NASA for shielding testing. Aspects of the test, reported in this and companion papers [5][6][7][8][9][10][11][12] , are the examination of noise shielding parameters (such as engine location, vertical and nozzle configurations) with regard to noise emission, and the determination of the noise spectra, levels, and directivity of the base vehicle and its components. Finally, the results from this test are used to support the noise assessment 7 of this HWB design and to validate the "low noise" characteristics of this aircraft concept.…”

Section: Introductionmentioning

confidence: 99%

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Shielding of Turbomachinery Broadband Noise from a Hybrid wing Body Aircraft Configuration

Hutcheson

Brooks

Burley

et al. 2014

20th AIAA/CEAS Aeroacoustics Conference

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The results of an experimental study on the effects of engine placement and vertical tail configuration on shielding of exhaust broadband noise radiation are presented. This study is part of the high fidelity aeroacoustic test of a 5.8% scale Hybrid Wing Body (HWB) aircraft configuration performed in the 14-by 22-Foot Subsonic Tunnel at NASA Langley Research Center. Broadband Engine Noise Simulators (BENS) were used to determine insertion loss due to shielding by the HWB airframe of the broadband component of turbomachinery noise for different airframe configurations and flight conditions. Acoustics data were obtained from flyover and sideline microphones traversed to predefined streamwise stations. Noise measurements performed for different engine locations clearly show the noise benefit associated with positioning the engine nacelles further upstream on the HWB centerbody. Positioning the engine exhaust 2.5 nozzle diameters upstream (compared to 0.5 nozzle diameters downstream) of the HWB trailing edge was found of particular benefit in this study. Analysis of the shielding performance obtained with and without tunnel flow show that the effectiveness of the fuselage shielding of the exhaust noise, although still significant, is greatly reduced by the presence of the free stream flow compared to static conditions. This loss of shielding is due to the turbulence in the model near-wake/boundary layer flow. A comparison of shielding obtained with alternate vertical tail configurations shows limited differences in level; nevertheless, overall trends regarding the effect of cant angle and vertical location are revealed. Finally, it is shown that the vertical tails provide a clear shielding benefit towards the sideline while causing a slight increase in noise below the aircraft.

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Section: Effect Of Engine Location On Noise Shieldingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Shielding of Turbomachinery Broadband Noise from a Hybrid wing Body Aircraft Configuration

Hutcheson

Brooks

Burley

et al. 2014

20th AIAA/CEAS Aeroacoustics Conference

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“…The error associated with the latter assumption was quantified to be on the order of less than 0.25 dB spectrally. 22 Not all (BENS, airframe or jet noise) data were obtained at the correct flight Mach number, engine thrust setting an/or angle-of-attack indicated in Table 2. Thus, additional scaling and adjustments to the measured noise levels were developed and applied (third box of Fig.…”

Section: Acoustic Data Processing and Noise Scalingmentioning

confidence: 99%

“…Jet noise measurements were obtained for a limited range of engine cycles and jet configurations 22 . For the present study, only the jet noise data obtained when the engine nacelles are at x/D=2.5 with the optimized PAA chevrons installed are used.…”

Section: Cjes: Jet Noisementioning

confidence: 99%

Noise Scaling and Community Noise Metrics for the Hybrid Wing Body Aircraft

Burley

Brooks

Hutcheson

et al. 2014

20th AIAA/CEAS Aeroacoustics Conference

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An aircraft system noise assessment was performed for the hybrid wing body aircraft concept, known as the N2A-EXTE. This assessment is a result of an effort by NASA to explore a realistic HWB design that has the potential to substantially reduce noise and fuel burn. Under contract to NASA, Boeing designed the aircraft using practical aircraft design principles with incorporation of noise technologies projected to be available in the 2020 timeframe. NASA tested a 5.8% scale-model of the design in the NASA Langley 14-by 22-Foot Subsonic Tunnel to provide source noise directivity and installation effects for aircraft engine and airframe configurations. Analysis permitted direct scaling of the model-scale jet, airframe, and engine shielding effect measurements to full-scale. Use of these in combination with ANOPP predictions enabled computations of the cumulative (CUM) noise margins relative to FAA Stage 4 limits. The CUM margins were computed for a baseline N2A-EXTE configuration and for configurations with added noise reduction strategies. The strategies include reduced approach speed, over-the-rotor liner and soft-vane fan technologies, vertical tail placement and orientation, and modified landing gear designs with fairings. Combining the inherent HWB engine shielding by the airframe with added noise technologies, the cumulative noise was assessed at 38.7 dB below FAA Stage 4 certification level, just 3.3 dB short of the NASA N+2 goal of 42 dB. This new result shows that the NASA N+2 goal is approachable and that significant reduction in overall aircraft noise is possible through configurations with noise reduction technologies and operational changes. Nomenclature ANOPP = NASA's aircraft noise prediction program 1 ANOPP2 = NASA's aircraft noise prediction program2, a multi-fidelity framework AOA = angle of attack, degrees AP = approach flight condition BENS = broadband engine noise simulators BPR = engine bypass ratio CB = cutback flight conditionThis material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. AIAA Aviation 2 CJES = compact jet engine simulators CUM = cumulative noise (summation of takeoff, cutback and approach EPNL), EPNdB D = fan nozzle exit diameter, ft. dB = decibel EPNL = effective perceived noise level, dB, also referred to as EPNdB FLOPS = flight optimization system 2 f = frequency HWB = hybrid wing body LE = leading edge L/D = lift/drag M = Mach number PNL = perceived noise level, dB PNLT = tone-corrected perceived noise level, dB R = distance from source to observer SF = model-scale/full-scale = 0.058 SFC = specific fuel consumption SL = sideline (full-throttle flight condition) certification point SPL = sound pressure level X = axial coordinate, ft. Greek φ = azimuthal directivity angle, degrees θ = polar directivity angle, degrees Subscript fs = full-scale ms = model-scale nb = narrowband

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“…If the surface extends beyond the flight stream edge it will produce additional background noise by its interaction with the flight stream shear layer. If the entire vehicle is represented, such as in the Hybrid Wing Body (HWB) test in Langley's 14x22 tunnel, 4 then the scale factor of the model is often very large and the model-scale frequencies of interest are exceedingly high. If a partial vehicle is used, such as in initial explorations of the HWB jet noise problem, 5 the scale factor can be more modest, but it is critical that all aspects of the vehicle that impact the sound generation and propagation be properly represented.…”

Section: Figure 1 Conceptual Supersonic Airliner (Left) and Scaled Acmentioning

confidence: 99%

Testing Installed Propulsion For Shielded Exhaust Configurations

Bridges

Podboy

Brown

2016

22nd AIAA/CEAS Aeroacoustics Conference

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Jet-surface interaction (JSI) can be a significant factor in the exhaust noise of installed propulsion systems. Tests to further the understanding and prediction of the acoustic impacts of JSI have been described. While there were many objectives for the test, the overall objective was to prepare for a future test validating the design of a low-noise, lowboom supersonic commercial airliner. In this paper we explore design requirements for a partial aircraft model to be used in subscale acoustic testing, especially focusing on the amount of aircraft body that must be included to produce the acoustic environment between propulsion exhaust system and observer. We document the dual-stream jets, both nozzle and flow conditions, which were tested to extend JSI acoustic modeling from simple singlestream jets to realistic dual-stream exhaust nozzles. Sample observations are provided of changes to far-field sound as surface geometry and flow conditions were varied. Initial measurements are presented for integrating the propulsion on the airframe for a supersonic airliner with simulated airframe geometries and nozzles. Acoustic impacts of installation were modest, resulting in variations of less than 3 EPNdB in most configurations.

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Jet Noise Shielding Provided by a Hybrid Wing Body Aircraft

Cited by 26 publications

References 19 publications

Shielding of Turbomachinery Broadband Noise from a Hybrid wing Body Aircraft Configuration

Shielding of Turbomachinery Broadband Noise from a Hybrid wing Body Aircraft Configuration

Noise Scaling and Community Noise Metrics for the Hybrid Wing Body Aircraft

Testing Installed Propulsion For Shielded Exhaust Configurations

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