Evaluation of two inflow control devices for flight simulation of fan noise using a JT15D engine

Jones, W. Linwood; Mcardle, J. G.; Homyak, L.

doi:10.2514/6.1979-654

Cited by 8 publications

(4 citation statements)

References 2 publications

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“…Jones et al [26] describe noise measurements of a static JT15D engine mated with two separate ICD designs -one internal to the engine inlet, and one external. Their results indicated that both ICDs led to significantly smoother inflow indicated by a sharp reduction in BPF tones.…”

Section: Turbulence Ingestionmentioning

confidence: 99%

“…The results of Preisser and Chestnutt for a static fan with subsonic blade tip speeds with and without an ICD, along with the results of Jones et al [26] and supplementary flight test results [27] have been used to build a general prediction of this effect on the blade passage frequency tone as shown in Figure 7a. Most of the noise from turbulence ingestion is radiated at a ninety degree angle to the inlet direction, which corresponds to the nearest point of an aircraft flyover, and so is likely to strongly influence system noise.…”

Section: Turbulence Ingestionmentioning

confidence: 99%

“…To model the higher harmonics (up to 4BPF), the noise levels are subtracted by 3 dB for each harmonic to model a decreasing effect of BLI with increasing BPF harmonic. Limited data from Jones et al [26], Clark et al [28], and Koch [29] suggest that higher harmonics are affected by nearly the same amount as the fundamental tone, but because these data are more limited and less applicable to the physical scenario at hand, the use of a 3 dB subtraction for each harmonic represents a conservative choice to predict this effect.…”

Section: Mean Flow Distortionmentioning

confidence: 99%

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Aircraft System Noise Assessment of the NASA D8 Subsonic Transport Concept

Clark

Thomas

Guo³

2018

2018 AIAA/CEAS Aeroacoustics Conference

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A vehicle-level noise assessment has been performed for the NASA D8 concept aircraft (ND8) in the NASA Advanced Air Transport Technology Project portfolio. The NASA research-level Aircraft NOise Prediction Program (ANOPP-Research) was used to predict the noise from each source component on the ND8 to build up a noise estimate for the full aircraft. The propulsion airframe aeroacoustic (PAA) effects of the ND8, namely boundary layer ingestion (BLI) with its influence on fan noise, and the noise shielding, reflection, and diffraction mechanisms of the unconventional airframe, were empirically modeled using experimental data. Noise reduction technologies appropriate to the 2025-2035 time frame were included in this study. Including all technologies and PAA effects, the ND8 is predicted to have a cumulative margin to the Stage 4 certification metric of only 7.4 EPNdB. Boundary layer ingestion is predicted to have a detrimental impact on cumulative noise levels on the order of 15 EPNdB. Fan noise is seen to be the primary noise source at all three certification points, even if the BLI noise impact could be entirely suppressed. The impact of engine noise shielding by the airframe is limited by a lack of aft shielding and the presence of horizontal tail reflections in the aft direction. The physical constraint on engine size by the pi-tail is seen as a potential barrier to engine noise reduction through the corresponding limitation on fan bypass ratio. Mildly reduced climb performance (compared to similar reference aircraft) does not provide any benefit through increased noise propagation distance. If the boundary layer ingestion noise penalty could be suppressed such that BLI would have no effect on noise, the cumulative margin to Stage 4 would increase to 22.4 EPNdB, still below the NASA Mid Term goal of 32-42 EPNdB.

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Section: Turbulence Ingestionmentioning

confidence: 99%

Section: Turbulence Ingestionmentioning

confidence: 99%

Section: Mean Flow Distortionmentioning

confidence: 99%

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Aircraft System Noise Assessment of the NASA D8 Subsonic Transport Concept

Clark

Thomas

Guo³

2018

2018 AIAA/CEAS Aeroacoustics Conference

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“…The approach to controlling the inflow for flight simulation in static tests has evolved around the concept of inlet honeycomb-grid flow conditioners which must be acoustically transparent over the frequency range of interest. Figure 4 shows the range of inflow control devices (ICD's) investigated at NASA Lewis (11,12,13,14). The sizes of the external devices, Figs ranged from roughly 4 to 2 fan diameters.…”

Section: Mechanism Identificationmentioning

confidence: 99%

Aircraft Turbofan Noise

Groeneweg

Rice

1983

Volume 5: Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; Process Industries

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Recent advances in the understanding of turbofan noise generation and suppression in aircraft engines are reviewed with particular emphasis on NASA research. The review addresses each link in the chain of physical processes which connect unsteady flow interactions with fan blades to far field noise. Mechanism identification and description, duct propagation, radiation and acoustic suppression are discussed. Recent advances in the experimental technique of fan inflow control assure that in-flight generation mechanisms are not ma.,ked by extraneous sources in static tests. Rotor blade surface pressure and wake velocity measurements aid the determination of the types and strengths of the generation mechanisms. Approaches to predicting or measuring acoustic mode content, optimizing treatment impedance to maximize attenuation, translating impedance into porous wall structure and interpreting far field directivity patterns are illustrated by comparisons of analytical and experimental results. A persistent theme of the review is the interdependence of source and acoustic treatment design to minimize far field noise. Areas requiring further research are discussed and the relevance of aircraft turbofan results to quieting other turbomachinery installations is addressed.

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