Abstract
Atomization and Sprays, 24 (4): 303–348 (2014) INJECTION OF WATER-IN-OIL EMULSION JETS INTO A SUBSONIC CROSSFLOW: AN EXPERIMENTAL STUDY Chris D. Bolszo, Vincent G. McDonell, ∗ Guillermo A. Gomez, & G. Scott Samuelsen Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697-3550, USA Address all correspondence to Vincent G. McDonell E-mail: mcdonell@ucicl.uci.edu Original Manuscript Submitted: 8/6/2013; Final Draft Received: 11/13/2013 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 charac- teristics 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 π 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 quanti- fied 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 addi- tional primary breakup mode for emulsions, interfacial tension breakup, is identified and observed to influence spray plume development and droplet size. KEY WORDS: jet in crossflow, jet penetration, droplet size, interfacial tension, laser diffraction spectroscopy, high-speed cinematography, Buckingham π theorem 1. INTRODUCTION In many applications, liquid atomization is achieved by injecting a column of liquid as a plain jet, perpendicularly (or angles near to) into a gaseous flow. This strategy has been utilized for various combustion systems including rocket propulsion, turbofan, turbojet, c 2014 by Begell House, Inc.
Highlights
In many applications, liquid atomization is achieved by injecting a column of liquid as a plain jet, perpendicularly into a gaseous flow
Reynolds Number (ReN) varied between two target values of 1600 and 3300 for neat DF2 (Φ = 0.00), which corresponds to an injector Cd varying from 0.65 to 0.70 for the 0.72 mm and 0.57 mm diameter nozzles
To establish the expected breakup mode for the conditions studied, the current test cases are plotted on a q versus Weaero regime map (Wu et al, 1998) in Fig. 7, which indicates a difference in dominant breakup behavior between the neat and emulsion cases
Summary
Liquid atomization is achieved by injecting a column of liquid as a plain jet, perpendicularly (or angles near to) into a gaseous flow. This strategy has been utilized for various combustion systems including rocket propulsion, turbofan, turbojet, 1044–5110/14/$35.00 ⃝c 2014 by Begell House, Inc. NOMENCLATURE. Dimensionless numbers and abbreviations Bo Bond number Cd discharge coefficient CD drag coefficient Ca capillary number D32 Sauter mean diameter D32d discrete phase. The jet in a crossflow problem has been studied for half a century (Leong, 2000; Leong et al, 2001) Progress on understanding this injection strategy involves investigating and modeling the liquid breakup and resulting spray plume structure. Correlation equations have proposed different forms of influencing variables, grouping of variables to predict liquid trajectories within the gaseous environment (Wu et al, 1998; Becker and Hassa, 2002)
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