Droplet Size and Evaporation Rate within a Two-Phase Flow by Morphology-Dependent Resonances in the Optical Spectra.
Abstract
In two-phase chemically reacting flows, the size, shape, and chemical content of fuel droplets affect combustion and their chemical by-products. A new in-situ and nonintrusive optical technique has been developed which provides highly accurate (one part in 10000 - 100,000) size and shape determination, as well as provide chemical speciation of the majority species forming the droplet. This all-optical technique uses the morphology-dependent resonances (MDRs) of spheres, spheroids, or any shape that enables an internal wave to travel around a great circle with appropriate phase shift. These MDRs in the fluorescence spectra of dye-doped droplets flowing in a linear stream have also provided information on: (1) evaporation rate of interacting droplets flowing in the ambient or heated environment; (2) condensation rate of interacting droplets flowing in a saturated vapor; and (3) surface tension and bulk viscosity of individual droplets which have been perturbed by a laser beam so as to cause slight shape distortions, e.g., from spheres to oblate or prolate spheroids. MDRs can provide wavelength selective high Q optical feedback for the internally generated fluorescent and Raman radiation. By using this high optical feedback, lasing from individual dye-tagged droplets of approx. 20 micron radius has been achieved. The potential of using bright lasing droplets as markers in flow diagnostics is promising. Stimulated Raman scattering from individual droplets of approx. 20 micron radius has been achieved. Keywords: Liquid droplets; Lorenz/Mie formalism; Dynamic surface tension; Morphology-dependent resonances.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 10, 1985
- Accession Number
- ADA158931
Entities
People
- B. T. Chu
- M. B. Long
- R. K. Chang
Organizations
- Yale University