Mechanical Engineering, Chemical and Biological Engineering
Journal or Book Title
International Journal of Multiphase Flow
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 white-beam 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 testing. Additionally, a novel method of estimating the intact length of the spray from different X-ray techniques, that uses broadband illumination, is presented.
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Bothell, Julie K.; Machicoane, Nathanael; Li, Danyu; Morgan, Timothy B.; Aliseda, Alberto; Kastengren, Alan L.; and Heindel, Theodore J., "Comparison of X-ray and optical measurements in the near-field of an optically dense coaxial air-assisted atomizer" (2020). Mechanical Engineering Publications. 400.
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