Evolution of swirl in two-dimensional-nozzle flow

Der, J.; Chu, Chong-Wei; Hunt, B. L.; Lorincz, D. J.

doi:10.2514/3.44759

Cited by 8 publications

(1 citation statement)

References 8 publications

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“…Der et al [98] applied swirl to a 4:1 aspect ratio rectangular nozzle in water tunnel experiments. Their results indicated that the swirl split up to form two co-rotating vortices which filled the rectangular nozzle.…”

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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Swirling flows in circular-to-rectangular transition ducts

Miau

Lin

Chen

et al. 1996

Experiments in Fluids

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Swirling flows in three circular-to-rectangular transition ducts, each of them with an aspect ratio of 2.0 at the rectangular exit, have been studied experimentally. The swirling flows were produced by swirlers whose vane angles were at 5 ~ 10 ~ and 20 ~ inclinded to the incoming flow, respectively. Flow visualization experiments were made at selected cross-sectional planes in the transition ducts. Pressure and velocity measurements were obtained on the contoured duct walls and at the rectangular exit planes, respectively. The results show that the swirling flow pattern evolves into a skewed structure at the exit plane which, in connection with the wall pressure distributions, is asymmetric with respect to the centerline of either the top and bottom walls or the side walls. Moreover, an analysis based on the mean streamwise vorticity equation with the velocity data obtained immediately downstream of the rectangular exit plane indicates that the cross-stream Reynolds stress plays an important role in transporting the streamwise vorticity of the swirling flow into the surrounding fluid.

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Experimental Study on Infrared Radiation Characteristics and Matching Performance of Low-Observable Nozzles

Shi,

Zhou,

et al. 2024

Journal of Propulsion and Power

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Infrared stealth performance is one of the most crucial criteria for modern warplanes. The low-observable nozzle suppresses the infrared radiation by shielding the high-temperature engine components and enhancing the exhaust plume mixing with the atmosphere, thereby improving warplane survivability. Using a Fourier transform infrared spectrometer, the infrared radiation characteristics of two low-observable nozzles, including a two-dimensional nozzle and a serpentine nozzle, were measured in this paper. The nozzles were mounted on a micro-turbojet engine, and the variations of engine thrust, exhaust gas temperature, and fuel consumption rate were also measured to evaluate the matching performance of low-observable nozzles. The results show that the engine exhaust temperature rises after installing the low-observable nozzles. The two-dimensional nozzle has a maximum effect of 1.3% on the fuel consumption rate, and the serpentine nozzle has a maximum impact of 5%. The influence of low-observable nozzles on engine thrust is less than 1.9%. The infrared radiation intensity of the two-dimensional nozzle increases by 9% when the detection angle is [Formula: see text] compared to the axisymmetric nozzle, while the serpentine nozzle decreases by 7%. When the detection angle is [Formula: see text], both low-observable nozzles achieve more than a 70% reduction in infrared radiation intensity.

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Evolution of swirl in two-dimensional-nozzle flow

Cited by 8 publications

References 8 publications

A review of jet mixing enhancement for aircraft propulsion applications

A review of jet mixing enhancement for aircraft propulsion applications

Swirling flows in circular-to-rectangular transition ducts

Experimental Study on Infrared Radiation Characteristics and Matching Performance of Low-Observable Nozzles

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