Jet noise suppression by swirling the jet flow

Schwartz, Ira R.

doi:10.2514/6.1973-1003

Cited by 8 publications

(6 citation statements)

References 2 publications

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“…In the 1970s, however, swirl was studied as a possible means of reducing jet noise during the Concorde noise reduction programme. This seems to have been prompted by experimental, full-scale engine studies by Schwartz [83,84], which appeared to show jet noise reductions in the presence of swirl. Subsequent work, however, questioned the validity of Schwartz's noise comparisons [85].…”

Section: Swirlmentioning

confidence: 99%

A review of jet mixing enhancement for aircraft propulsion applications

Knowles

Saddington

2006

Proceedings of the Institution of Mechanical Engineers, Part G:

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This article reviews techniques applicable to enhancing the mixing of jets, with particular emphasis on infrared (IR) signature reduction of high-speed jets. Following a brief introduction to the IR signature of jet plumes and the fundamentals of jet mixing, this paper discusses rapid mixing technologies under the categories of: geometric modifications (to the nozzle); high shear stress mixing; normal stress mixing; self-acoustic excitation; external acoustic excitation; mechanically oscillated; self-oscillated. It is shown that mixing enhancements of the order of 100 per cent are possible with some techniques and that by combining techniques this can be increased by at least as much again. Simple geometric calculations are presented which demonstrate that with rectangular nozzles such high levels of mixing enhancement may be necessary in order to reduce IR signature. Some apparent rapid mixing technologies, however, have been shown to increase jet spreading without increasing entrainment, whereas other techniques can reduce entrainment as easily as they can increase it.

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Section: Swirlmentioning

confidence: 99%

A review of jet mixing enhancement for aircraft propulsion applications

Knowles

Saddington

2006

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…This enhances the mixing between the fuel and the oxidizer and acts as a flame holder in the combustion chamber. Also, the addition of swirling flows causes a reduction of noise levels (3,4) . Apart from these applications, swirling flows are used in confined configurations such as combustion, cyclone separators and pipe flow systems, systems for transport of sand, gravel (5)(6)(7)(8)(9) and so on.…”

Section: Introductionmentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

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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“…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%

“…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. 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.…”

Section: Introductionmentioning

confidence: 99%

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

Cited by 8 publications

References 2 publications

A review of jet mixing enhancement for aircraft propulsion applications

A review of jet mixing enhancement for aircraft propulsion applications

Pipe jet noise reduction using co-axial swirl pipe

Drag Management in High Bypass Turbofan Nozzles for Quiet Approach Applications

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