Characterization of three-dimensional dense spray visualization techniques

Halls, Benjamin R.; Radke, Christopher D.; Heindel, Theodore J.; Lohry, William; Zhang, Song; Meyer, Terrence R.; Lightfoot, Malissa; Danczyk, Stephen A.; Schumaker, Stephen A.; Roy, Sukesh; Gord, James R.; Kastengren, Alan L.

doi:10.2514/6.2013-477

Cited by 3 publications

(1 citation statement)

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“…Additionally, the capabilities, advantages, and disadvantages of each technique are discussed. A complementary study using an impinging jet spray and structured light and 3-D X-ray CT reconstruction was completed by Halls et al (2013). Using the same impinging jet spray setup, Halls et al (2014) compared 2-D and 3-D mass distribution measures to focused-beam measurements.…”

Section: Introductionmentioning

confidence: 99%

Comparison of X-ray and optical measurements in the near-field of an optically dense coaxial air-assisted atomizer

Bothell

Machicoane

et al. 2020

International Journal of Multiphase Flow

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Understanding the near-field region of a spray is integral to optimization and control efforts because this region is where liquid break-up and spray formation occurs, setting the conditions under which the spray dynamics evolve under the gas turbulence and droplet inertia.However, the high optical density of this region complicates measurements; thus, it is not yet well characterized. This paper is intended to compare four of the leading experimental techniques that are being used or developed to study the near-field region of a spray. These techniques are shadowgraphy, tube source X-ray radiography, high-speed synchrotron whitebeam X-ray imaging, and synchrotron focused-beam X-ray radiography. Each of these methods is applied to a canonical spray, using the same nozzle, under identical flow conditions.Synchrotron focused-beam radiography shows that a time-averaged Gaussian liquid distribution is a valid approximation very near the nozzle, before the core has broken apart. The Gaussian behavior continues as the spray progresses further downstream, showing self-similarity. A spray angle can be defined from the linear spreading of the Gaussian intensity distribution with downstream distance. The spray angle found from shadowgraphy is validated with focused-beam Second revision for submission to: International Journal of Multiphase Flow 2 testing. Additionally, a novel method of estimating the intact length of the spray from different X-ray techniques, that uses broadband illumination, is presented.

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Section: Introductionmentioning

confidence: 99%

Comparison of X-ray and optical measurements in the near-field of an optically dense coaxial air-assisted atomizer

Bothell

Machicoane

et al. 2020

International Journal of Multiphase Flow

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Three-dimensional imaging of swirled spray injection in a generic aero engine burner under realistic operating conditions

Klinner

Willert

2021

Exp Fluids

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Tomographic shadowgraph imaging is applied to reconstruct the instantaneous three-dimensional spray field immediately downstream of a generic aero engine fuel injector. Within the swirl passage of the injector model, a single kerosene jet undergoes air-blast atomization in a cross-flow configuration at Weber numbers of $$\text {We}=360-770$$ We = 360 - 770 , air pressures of $$p_a=4-7\,\text{ bar }$$ p a = 4 - 7 bar and air temperatures of $$T_a=440-570\,\text{ K }$$ T a = 440 - 570 K . High-speed, high magnification shadowgraphy is used to visualize the initial fuel atomization stages within the fuel injector before the spray enters the spray chamber. The 4-camera tomographic measurement setup is described in detail and includes a depth-of-field analysis with respect to droplet size based on Mie simulations and calibration data of the point-spread function. For a volume size of $$16\times 13\times 10\,\text{ mm}^3$$ 16 × 13 × 10 mm 3 , the smallest resolvable droplet diameter is estimated to be $$d=10\,\mu \text{ m }$$ d = 10 μ m within the focal plane and increases to $$d \approx 20\,\mu \text{ m }$$ d ≈ 20 μ m toward the edges of the volume. Droplet velocities above the resolution limit were retrieved by 3-d cross-correlation of two volumetric reconstructions recorded at two consecutive time-steps. This is accompanied by an error analysis on the random error dependency on the camera viewing geometry. The results indicate increasing motion and fluctuations of the spray tail with increasing temperature and Weber number. Validation against PDA data further downstream of the burner plate revealed consistency for size classes $$d=10\,\mu \text{ m }$$ d = 10 μ m and $$d=15\,\mu \text{ m }$$ d = 15 μ m . Deviations from PDA occur in regions with strong velocity gradients due to different spatial resolutions, the presence of reconstruction ambiguities (ghost particles), uncertainties inherent to the two-frame cross-correlation of spray volumes and the finite LED pulse duration. Graphical Abstract

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