Atomization and Sprays, Vol.24, No.4, 303-348, 2014
INJECTION OF WATER-IN-OIL EMULSION JETS INTO A SUBSONIC CROSSFLOW: AN EXPERIMENTAL STUDY
In this work, the influence of introducing water in oil, as an emulsion, in a liquid jet injected into a gaseous crossflow is investigated. Of particular interest is the relationship between emulsion characteristics on spray penetration and spray droplet size. Tests are conducted at atmospheric conditions, with liquid jet-to-crossflow momentum flux ratios spanning 30-120, and water addition to 40% by mass. Gas velocities range from 20 to 80 m/s and liquid velocities from 10-20 m/s are considered. Backlit high-speed video is used to document the overall spray characteristics and laser diffraction is used to measure the spray droplet sizes. Sobel edge filtering and intensity thresholding are utilized to establish the spray plume upper edge for the spray morphology, which was used to establish the spray trajectory. The Buckingham pi theorem is used to identify the important functional groupings for the current physical problem. For time-averaged trajectories, an existing liquid jet trajectory equation form from Wu and co-workers successfully correlates the penetration of emulsion spray plumes. These findings show that momentum flux of the bulk emulsion jet remains the dominant factor governing jet penetration. The influence of emulsification on spray plume droplet size distributions is quantified in the current work. A new nondimensional quantity is proposed to account for the effect of body forces and repulsive interfacial tension on correlating breakup. For the conditions studied, an additional primary breakup mode for emulsions, interfacial tension breakup, is identified and observed to influence spray plume development and droplet size.