Noise of Swirling Exhaust Jets

Lu, Huiping; Ramsay, James W.; Miller, David L.

doi:10.2514/3.60673

Cited by 23 publications

(7 citation statements)

References 4 publications

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“…In the 1970s, Schwartz (3,4) proposed that noise intensity can be reduced by using vanes. Later, Lu et al (17) developed an experimental work to study the noise of the swirling exhaust flows. The swirling jet noise was higher than the non-swirling jets, except at angles less than 40°from the jet axis.…”

Section: Acoustic Characteristicsmentioning

confidence: 99%

Pipe jet noise reduction using co-axial swirl pipe

Balakrishnan

Srinivasan

2017

Aeronaut. j.

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The present experimental work highlights the acoustic far field and flow field characteristics of confined co-axial swirling pipe jets. Co-axial confinements with six vanes at angles of 0°, 20° and 40° are considered here. Two pipe lengths of L/D=0.5 and 2 are studied. The Mach numbers studied range from 0.85 to 1.83. An increase in the pipe length causes suppression of the transonic tones in non-swirl pipe jets. Swirl reduces the low frequency noise components and increases the high-frequency components compared to non-swirl jet. The broadband shock associated noise is mitigated by the swirl pipe jets. However, the screech tone is completely eliminated by the swirl pipe jets. Further, swirl pipe jets radiate low levels of noise at all the emission angles compared to non-swirl pipe jets, for both the pipe length cases at supersonic Mach numbers. Increase in the pipe length enhances the shock associated noise and OASPL for the non-swirl pipe jet. Centreline pitot survey and schlieren visualisation show a reduction in core length, reduction in the number of shock cells, weakening/destruction of the shock cells by the swirl pipe jets compared to the non-swirl pipe jets.

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Section: Acoustic Characteristicsmentioning

confidence: 99%

Pipe jet noise reduction using co-axial swirl pipe

Balakrishnan

Srinivasan

2017

Aeronaut. j.

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“…Lu et al [12] measured the noise and flow characteristics of model swirling jets and reported that swirling jet noise is broadband in nature similar to nonswirling jet noise. The noise levels increase with swirl angle and decrease with increasing pressure ratio and total temperature.…”

Section: Introductionmentioning

confidence: 99%

“…They also noted differences in noise from internal and external plug nozzles. The work of Lu et al [12] was motivated in part by the previous work of Schwartz [13], who showed jet noise suppression in an engine application with swirling flow. Schwartz [13] obtained a ratio of 3 dB overall sound power reduction to 1% of thrust loss for a Pratt & Whitney JT15D-1 bypass flow engine by swirling a part of the primary flow.…”

Section: Introductionmentioning

confidence: 99%

“…Schwartz [13] obtained a ratio of 3 dB overall sound power reduction to 1% of thrust loss for a Pratt & Whitney JT15D-1 bypass flow engine by swirling a part of the primary flow. Lu et al [12] noted that the experiments of Schwartz included more than jet noise sources alone, and concluded that considerable further testing of swirling jet flow and noise, especially under the influence of a parallel mean flow, was required to advance the understanding of the acoustic signature of such exhaust flows. The current definition does not include the rematching of gas turbine components when the device is deployed.…”

Section: Introductionmentioning

confidence: 99%

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Drag Management in High Bypass Turbofan Nozzles for Quiet Approach Applications

Shah

Robinson

Price

et al. 2013

Journal of Turbomachinery

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The feasibility of a drag management device that reduces engine thrust on approach by generating a swirling outflow from the fan (bypass) nozzle is assessed. Deployment of such “engine air-brakes” (EABs) can assist in achieving slower and/or steeper and/or aeroacoustically cleaner approach profiles. The current study extends previous work from a ram air-driven nacelle (a so-called “swirl tube”) to a “pumped” or “fan-driven” configuration and also includes an assessment of a pylon modification to assist a row of vanes in generating a swirling outflow in a more realistic engine environment. Computational fluid dynamics (CFD) simulations and aeroacoustic measurements in an anechoic nozzle test facility are performed to assess the swirl-flow-drag-noise relationship for EAB designs integrated into two NASA high-bypass ratio (HBPR), dual-stream nozzles. Aerodynamic designs have been generated at two levels of complexity: (1) a periodically spaced row of swirl vanes in the fan flowpath (the “simple” case), and (2) an asymmetric row of swirl vanes in conjunction with a deflected trailing edge pylon in a more realistic engine geometry (the “installed” case). CFD predictions and experimental measurements reveal that swirl angle, drag, and jet noise increase monotonically but approach noise simulations suggest that an optimal EAB deployment may be found by carefully trading any jet noise penalty with a trajectory or aerodynamic configuration change to reduce perceived noise on the ground. Constant speed, steep approach flyover noise predictions for a single-aisle, twin-engine tube-and-wing aircraft suggest a maximum reduction of 3 dB of peak tone-corrected perceived noise level (PNLT) and up to 1.8 dB effective perceived noise level (EPNL). Approximately 1 dB less maximum benefit on each metric is predicted for a next-generation hybrid wing/body aircraft in a similar scenario.

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“…Jet noise suppression by swirling the jet flow was stimulated by Schwartz 6 who obtained a ratio of 3dB overall sound power reduction to 1% of thrust loss for a Pratt & Whitney JT15D-1 bypass flow engine by swirling a part of the primary flow. Lu et al 7 measured the noise and flow characteristics of model swirling jets and report that swirling jet noise is broadband in nature similar to non-swirling jet noise. The noise levels increase with swirl angle and decrease with increasing pressure ratio and total temperature.…”

mentioning

confidence: 99%

Aeroacoustics of Drag-Generating Swirling Exhaust Flows

Shah¹,

Mobed²,

Spakovszky³

et al. 2010

AIAA Journal

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Aircraft on approach in high-drag and high-lift configuration create unsteady flow structures which inherently generate noise. For devices such as flaps, spoilers and the undercarriage there is a strong correlation between overall noise and drag such that, in the quest for quieter aircraft, one challenge is to generate drag at low noise levels. This paper presents a rigorous aero-acoustic assessment of a novel drag concept. The idea is that a swirling exhaust flow can yield a steady, and thus relatively quiet, streamwise vortex which is supported by a radial pressure gradient responsible for pressure drag.

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Noise of Swirling Exhaust Jets

Cited by 23 publications

References 4 publications

Pipe jet noise reduction using co-axial swirl pipe

Pipe jet noise reduction using co-axial swirl pipe

Drag Management in High Bypass Turbofan Nozzles for Quiet Approach Applications

Aeroacoustics of Drag-Generating Swirling Exhaust Flows

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