Noise of swirling exhaust jets

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

doi:10.2514/6.1976-510

Cited by 5 publications

(5 citation statements)

References 2 publications

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“…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]. One important consideration in understanding the behaviour of swirling flow is the radial variation of swirl velocity.…”

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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“…Even under the off-design conditions, such as takeoff and landing, the thrust loss still fell into an acceptable range (1–2%) with inlet swirl. Unfortunately, Lu 24 presented a disagreement with this conclusion. Knowles and Carpenter 25 stated that the reasonable radial distribution of swirl angle could effectively control mass flows of circular nozzles and would not cause obvious decrease of thrust.…”

Section: Introductionmentioning

confidence: 97%

Numerical research on the mixing mechanism of lobed mixer with inlet swirl in linear radial distribution

Lei

Zhang

Zhu

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part A:

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A detailed numerical simulation is presented to investigate the effects of inlet swirl and its radial distribution on the mixing mechanisms of a turbofan mixer with 12 lobes, by using the commercial ANSYS CFX solver and k-! SST model. The core-to-bypass temperature ratio and pressure ratio were set to 2.59 and 0.97, respectively, giving the Mach number of 0.66 and bypass ratio of 2.65 at mixing nozzle outlet. In the core inlet, the swirl angle was raised from 0 to 30 in a uniform or linear radial distribution manner. The inlet swirl and its radial gradient did enhance the development, interaction, and dissipation of the vortices downstream of lobed mixer, resulting in accelerating the lobed jet mixing. When the inlet swirl was less than 20 , the total pressure and thrust loss increments of lobed jet were acceptable and no more than 0.26% and 1.57%, respectively, compared with the baseline case. The results also showed that the three-dimensional separation bubble on center-body and the backflows along jet axis at the rail of center-body, resulting from the swirling flow between lobes' trough and center-body, were the dominant sources of total pressure and thrust losses for all cases with inlet swirl. And, reasonable radial distribution of inlet swirl could inhibit the aforementioned 3D separation and backflow, and thus limited the increment of jet mixing loss favorably.

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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: 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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Noise of swirling exhaust jets

Cited by 5 publications

References 2 publications

A review of jet mixing enhancement for aircraft propulsion applications

A review of jet mixing enhancement for aircraft propulsion applications

Numerical research on the mixing mechanism of lobed mixer with inlet swirl in linear radial distribution

Pipe jet noise reduction using co-axial swirl pipe

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