Fluorescence imaging of mixing flowfields and comparisons with computational fluid dynamic simulations

Gaston, M.; Houwing, A. F. P.; Mudford, N. R.; Danehy, Paul M.; Fox, J.S.

doi:10.1007/s00193-002-0151-4

Cited by 13 publications

(11 citation statements)

References 11 publications

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“…22b is misleading, as it appears quite similar to the mean without the injected jet, though the instantaneous realizations appear quite different. This observation is quite similar to that of Gaston et al 7 studying a similar swept compressive-expansive injector. They captured transverse (YZ) planes of NO PLIF, and showed that the injected jets are turned away from the centerline, following the same contours of the presumed counter-rotating vortex pair.…”

Section: B Effect Of Compressive Hypermixer On Secondary Injectionsupporting

confidence: 87%

“…Later studies to the same effect utilized PLIF of nitric oxide (NO) in a shock tunnel. [7][8][9] In particular, a baseline case of a planar hypermixing flowfield was compared to various castellated and compressive hypermixers, drawing much the same conclusion about the mixing enhancement.…”

Section: Introductionmentioning

confidence: 98%

“…[5][6][7][8][9][10][11][12][13][14][15][16][17][18] In this strategy, geometrically-induced pressure gradients are used to generate or increase the streamwise vorticity present in the flow. For strut-based schemes, this is often achieved through the use of alternating compressive and/or expansive surfaces on the trailing edge of the pylon, while for wall-based schemes it is achieved through oblique injection from a swept compressive ramp.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Scalar and Velocity Measurements in a Mach 3 Hypermixing Flowfield

Burns

Clemens

2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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Mach 3 hypermixer flowfields are studied by using scalar and velocity imaging techniques. Two strut-based hypermixer configurations are used that feature parallel gas injection through a castellated base with (i) expansive wedges flanking the base, and (ii) a combination of compressive and expansive wedges near the base. Two-component particle image velocimetry (PIV) is used to obtain the velocity fields, planar laser scattering (PLS) of condensed carbon dioxide gas is used to visualize the freestream flow structures, and planar laser-induced fluorescence (PLIF) of acetone vapor is used to tag the injected jet fluid. In the cases with no base injection, the two wakes show notable differences, with the compressive mixer entraining large quantities of freestream fluid within the wake in contrast to the expansive mixer. With the addition of base injection, the expansive mixer is found to induce notable transverse spread of the injected jet fluid though spanwise spread is limited. The compressive mixer enhances the spread of the injected fluid in both the spanwise and transverse directions. The velocity measurements show that rapid transverse spread of the jet in the compressive hypermixer is the result of a large transverse velocity component induced by the strong streamwise vortices. These vortices are so strong as to create a bifurcation of the jet fluid along the midplane of the hypermixer.

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Section: B Effect Of Compressive Hypermixer On Secondary Injectionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Scalar and Velocity Measurements in a Mach 3 Hypermixing Flowfield

Burns

Clemens

2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…Figure 13. Schematic diagram and images of PLIF studies of hypersonic mixing (82) . (a) Flow without injection; (b) Flow with fuel injection.…”

Section: Flow Imagingmentioning

confidence: 99%

Optical imaging techniques for hypersonic impulse facilities

2007

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The application of optical imaging techniques to hypersonic facilities is discussed and examples of experimental measurements are provided. Traditional Schlieren and shadowgraph techniques still remain as inexpensive and easy to use flow visualisation techniques. With the advent of faster cameras, these methods are becoming increasingly important for time-resolved high-speed imaging. Interferometry’s quantitative nature is regularly used to obtain density information about hypersonic flows. Recent developments have seen an extension of the types of flows that can be imaged and the measurement of other flow parameters such as ionisation level. Planar laser induced fluorescence has been used to visualise complex flows and to measure such quantities as temperature and velocity. Future directions for optical imaging are discussed.

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“…Laser-induced fluorescence 8 compared to single-point fluorescence measurements (LIF), lies in the ability to visualize relative species distributions over an entire planar cross section of the flow field, making it thus also a more complex technique. PLIF has been used for hypersonic flow visualisation (Fox et al, 2001a,b;Gaston et al, 2002), visualisation of a scramjet combustor (McIntyre et al, 1997), thermometry (Palma et al, 2003(Palma et al, , 1998Sutton et al, 1993) and velocimetry (Danehy et al, 2001.…”

Section: Laser-induced Fluorescencementioning

confidence: 99%

Temperature measurements in hypervelocity flows using thermally-assisted laser-induced fluorescence

Sopek¹

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Scramjet engines with their very high specific impulse have the potential to outperform rocket motors as a means of propelling hypersonic vehicles. The scope of this project is to determine temperatures in the scramjet combustor using an advanced optical diagnostic technique, namely laser-induced fluorescence. Presently, direct temperature measurements are not readily available for scramjets, due to three reasons. Firstly, commonly-used gauges for temperature measurements, such as thermocouples and heat transfer gauges would not survive or would be damaged at the extreme temperatures typically occurring in scramjets (around T = 1100 -2500 K), and therefore these gauges would not give accurate readings. Secondly, measurements with any gauges would be intrusive, and their presence in the flow might cause large disturbances. Thirdly, these gauges can only provide discrete, point measurements. Laser-induced fluorescence measurements present an optical non-intrusive technique to resolve temperatures in the combustor. Additionally, LIF measurements allow the temperatures in the combustor to be resolved at a higher spatial resolution than regular gauges. The new contribution made by this PhD project is the application of a sophisticated optical diagnostic technique, thermally-assisted laserinduced fluorescence, to the temperature measurements in the combustor of a supersonic combustion engine. The issues with the technique and the way it should be used for application to scramjet flows were explored. This required the development of the new knowledge and understanding of the spectroscopy that underpins the technique. The project is significant because, to the author's knowledge, this is the first time thermally-assisted LIF has been used for scramjet flows in a test facility. Currently available thermometry methods usually require averaged repeated experiments, thus causing high cost of experiments. This study represents successful single-shot scramjet temperature measurements. The project was approached theoretically (synthetic spectra), experimentally and numerically (CFD and LIF modelling).Radiation simulation programs providing synthetic OH spectra represent the theoretical part of this study, as they employ theoretical expressions for spectral calculations. The OH radical is an intermediate species in the combustion, created in high quantities, therefore allowing direct fluorescence measurements. In this work, three numerical codes were used -LIFBASE, SPARTAN and Photaura. SPARTAN and Photaura were modified in order to include the OH molecule. The results presented here show that OH spectra produced using these programs show very good agreement. All three programs give correct and reliable representation of the physical phenomena in the wavelength range studied.Experimental data was obtained through laser-induced fluorescence with a laser beam focused into the combustor exciting an OH molecule transition. The experiments were conducted in the T4 shock tunnel using a scramjet model. LIF measurements were performed t...

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Fluorescence imaging of mixing flowfields and comparisons with computational fluid dynamic simulations

Cited by 13 publications

References 11 publications

Scalar and Velocity Measurements in a Mach 3 Hypermixing Flowfield

Scalar and Velocity Measurements in a Mach 3 Hypermixing Flowfield

Optical imaging techniques for hypersonic impulse facilities

Temperature measurements in hypervelocity flows using thermally-assisted laser-induced fluorescence

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