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Atomization and Sprays
IF: 1.189 5-Year IF: 1.596 SJR: 0.814 SNIP: 1.18 CiteScore™: 1.6

ISSN Print: 1044-5110
ISSN Online: 1936-2684

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Atomization and Sprays

DOI: 10.1615/AtomizSpr.v6.i3.50
pages 331-351

MEASUREMENT OF THE EVAPORATION RATES OF CLOSELY SPACED FLOWING DROPLETS BY OPTICAL CAVITY RESONANCES

J. Christian Swindal
Department of Applied Physics and Center for Laser Diagnostics, Yale University, New Haven, Connecticut, USA
Gang Chen
Department of Applied Physics and Center for Laser Diagnostics, Yale University, New Haven, Connecticut, USA
Karl Scheschak
Department of Applied Physics and Center for Laser Diagnostics, Yale University, New Haven, Connecticut, USA
Richard K. Chang
Department of Applied Physics and Center for Laser Diagnostics, Yale University, New Haven, Connecticut, USA
Thomas A. Jackson
Air Force Aero-Propulsion Laboratory, Fuel and Lubrication Division, WRDC/POSF, Wright Patterson Air Force Base, Ohio, USA

ABSTRACT

The evaporation of liquid droplets in sprays can be altered by interactions between closely spaced particles. We discuss a nonintrusive optical measurement technique that is based on the optical cavity resonances of the droplets to determine droplet sizes and evaporation rates. The addition of small amounts of Rhodamine 6G laser dye into ethanol or ethanol/ acetone mixture droplets allows the droplets to lose at discrete wavelengths that correspond to the spectral positions of the droplet-cavity resonances. Measurements of the cavity resonance shift as the droplet evaporates permits determination of droplet size changes with a sensitivity of 1 nm in droplet radius change for droplets with a radius of 40 μm. We have determined the variation in evaporation rates among the leading and trailing droplets within a single segmented flowing stream, as well as between adjacent droplets that are flowing within a closely spaced 3 × 3 square array of continuous streams. Qualitative fluorescence images of the vapor produced by a continuous single stream of flowing acetone droplets demonstrate the existence of a vapor trail generated by the leading droplets flowing at 10 m/s.