Three-Way Spectral Decompositions of High-Performance Military Aircraft Noise

Neilsen, Tracianne B.; Vaughn, Aaron B.; Gee, Kent L.; Swift, S. Hales; Wall, Alan T.; Downing, J. Micah; James, Michael M.

doi:10.2514/1.j057992

Cited by 10 publications

(1 citation statement)

References 49 publications

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“…28–30 Work on spectral decomposition of engine noise is described in Refs. 31 and 32, and the identification of noise sources from aeroengine fans by using phased arrays has been reported. 33,34 Acoustic measurements have also been proposed as a means of deducing engine power settings during start-up and take-off, which are often not published by the airlines.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the free-space acoustic signature of a BBMF Rolls-Royce Merlin engine from 842 rpm to 2740 rpm

Bennett

2021

Proceedings of the Institution of Mechanical Engineers, Part G:

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A technique has been developed to analyse the free-space acoustic signature of the Rolls-Royce Merlin engine in order to provide diagnostic information relating to its performance. The work is motivated by a need to maintain the reliability and maximise the lifetime of this historic engine which is an important component of the aircraft operated by the UK Battle of Britain Memorial Flight (BBMF). For convenience, the data were extracted from the soundtrack of a video recording made whilst the aircraft was undergoing a full-power ground-run. The aim of the work is to generate information relating the individual firings of each cylinder and this is presented as a multi-level colour image. Here, the ignition time history for two revolutions (six ignitions) is shown vertically and corresponds to the bank of exhaust ports facing the microphone. Subsequent similar histories are presented along the horizontal time axis. The results are sensitive to engine speed variations, and a correlation between successive vertical columns is carried out to quantify this drift and adjust the data accordingly. Seven engine speeds from 842 to 2740 rpm are examined. The processed data illustrate that some speeds exhibit well-defined, single ignitions whereas others show varying degrees of after-firing type effects. At the higher engine speeds, it would seem that the cylinder ignition amplitudes become much more irregular, and the results for 2740 rpm indicate a breakdown in engine performance. The coefficient of variation (Cv) has been demonstrated as a measure of these factors. Finally, a technique has been proposed and demonstrated for the identification of individual cylinders in the firing sequence. The data acquisition process is relatively straight-forward and should not demand excessive time to cover a full range of engine speeds. With further investigations, it could be possible to readily relate the imaging results to specific engine faults.

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Section: Introductionmentioning

confidence: 99%

Analysis of the free-space acoustic signature of a BBMF Rolls-Royce Merlin engine from 842 rpm to 2740 rpm

Bennett

2021

Proceedings of the Institution of Mechanical Engineers, Part G:

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On the spectral shape and a second component of broadband shock-cell noise

Tam

2022

Journal of Sound and Vibration

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Evidence for nonlinear reflections in shock-containing noise near high-performance military aircraft

Vaughn

Leete

Gee

et al. 2021

The Journal of the Acoustical Society of America

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Skewness values for the pressure time derivative are greater at ground-based measurements near a tactical aircraft than they are at nearby off-ground locations. A possible explanation for this phenomenon is the occurrence of nonlinear, irregular shock reflections at the ground. Propagation angle, source location, and corresponding angle of incidence relative to the ground are estimated using a two-point cross correlation of windowed shock events. Nonlinear reflections are likely to occur based on the combination of angles of incidence and measured shock strengths and cause a pressure increase at the shock that is greater than twice the free-field pressure. The associated pressure increase at the shocks appears to enhance shock-related metrics at the ground compared to off-ground locations.

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Three-Way Spectral Decompositions of High-Performance Military Aircraft Noise

Cited by 10 publications

References 49 publications

Analysis of the free-space acoustic signature of a BBMF Rolls-Royce Merlin engine from 842 rpm to 2740 rpm

Analysis of the free-space acoustic signature of a BBMF Rolls-Royce Merlin engine from 842 rpm to 2740 rpm

On the spectral shape and a second component of broadband shock-cell noise

Evidence for nonlinear reflections in shock-containing noise near high-performance military aircraft

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