Liquid sprays play a key role in many engineering processes (e.g., food processing, coating and painting, 3D printing, fire suppression, combustion systems, etc.). The conditions at the nozzle exit have a large influence on the downstream spray characteristics. However, characterizing the spray in this region is extremely challenging because under most operating conditions the spray is optically dense. High intensity white beam X-ray imaging and focused beam radiography, like that available at the Advanced Photon Source (APS) at Argonne National Laboratory, can be used to produce time-resolved visualizations and measurements of the spray near-field region. In this study, high spatially-and temporally-resolved X-ray data are acquired of a canonical airblast atomizer consisting of coaxial water and air jets. The liquid is charged by flowing it through a metallic duct electrified to -5 kV with the motivation to enhance the atomization process. High-speed X-ray images and measured equivalent path lengths are compared with and without the electric potential and with and without gas swirl. It is shown that the electrification of the liquid needle has a negligible effect in the spray near-field for the conditions used in this study.

Atomization is useful in many applications including combustion, spray painting, and fire suppression. To form a more complete understanding of the atomization process, it is necessary to study the near-, mid-, and far-field regions of a spray. Previous studies from this group, as well as from collaborators, have explored the near-and mid-field regions of a canonical airblast atomizer under atmospheric conditions. To provide a more complete atomization assessment, experimental spray measurements in pressurized environments are necessary. The Chamber for Assorted Pressurized Spray sUrveiLlancE, or CAPSULE, has been designed and constructed to operate the canonical airblast atomizer at pressures up to 1 MPa and volumetric gas flow rates of nearly 4000 SLPM. The CAPSULE is a 190 L (50 gallon), 316L stainless steel pressure vessel equipped with six sight glasses to collect atomization data using multiple experimental techniques, including backlit imaging, Phase Doppler Particle Analysis (PDPA), and high-intensity X-ray radiography. The CAPSULE is fed by compressed air lines for both co-axial and swirl flow conditions. This paper provides an overview of the CAPSULE design, the major components in the flow loop, and the canonical airblast atomizer. Preliminary backlit imaging results are presented for ambient pressures in the range 0.1-0.5 MPa.

Liquid sprays play a key role in many engineering processes and the dynamics at the nozzle exit have a significant impact on the downstream spray characteristics. However, visualizing the spray in this region is extremely challenging because, under most operating conditions, the spray is optically dense. High intensity white beam X-rays, like those found at the Advanced Photon Source (APS) at Argonne National Laboratory, can be used to produce time-resolved measurements of the liquid-gas structures in the spray near-field region. In this study, high temporal and spatial resolution X-ray images were acquired at the 7-BM beamline at APS of an atomization process using a canonical airblast atomizer consisting of coaxial liquid and gas jets. Unique flow structures were observed under various operating conditions, including bag, ligament, wisp, droplet, and air bubble formation, as well as hollowing of the liquid core into a crown at the liquid needle exit. Conditions where these structures exist are presented and their impact on spray formation are discussed.

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