Aluminum droplet combustion in fluorine and mixed oxygen/fluorine containing environments

L. F. Ernst, F. L. Dryer, R. A. Yetter, T. P. Parr, D. M. Hanson-Parr

Research output: Contribution to journalConference articlepeer-review

12 Scopus citations


Experimental and numerical results are reported on the combustion of single aluminum (Al) droplets, 187 μm diameter, that were laser ignited in quiescent environments of SF6 and SF6/O2 or Ar mixtures. Combustion measurements consisted of luminosity versus time traces, photographic observations, and electron probe microanalysis (EPMA) and electron microscope inspection of condensed-phase products of combustion surrounding burn-intercepted droplets. Planar laser-induced fluorescence (PLIF) was employed to image the gaseous intermediate reaction species AlO during droplet combustion in SF6/O2 mixtures. Aluminum droplets burning in pure SF6 burned without condensed-phase products in the surrounding envelope flames. Accordingly, no condensed-phase products were found on surfaces of droplets captured by quenching into an inert environment. In SF6, classical d2 law burning behavior was observed. Droplets burned in SF6/Ar mixtures exhibited similar behavior, with diminished burning rates. Disruptive burning was not observed for pure SF6 or any of the SF6/Ar mixtures. Condensed-phase deposits on quench plates intercepting burning droplets showed the surrounding gaseous flame structure to consist of two zones for burning in SF6 and three zones in SF6/O2 mixtures. For each system, near the surface where the gas phase was aluminum rich, significant amounts of sulfur were found in the condensed products. PLIF showed the species profile of AlO to shift closer to the surface with increasing fluorine content in SF6/O2 mixtures. Experimental results were compared with a local equilibrium combustion model. The model predicted burn rates within 20% and qualitatively predicted radial profile speciation. As the O/F ratio was increased, the final equilibrium products were predicted to shift from AlF3 to AlF2O to Al2O3. The formation of AlF2O reduced condensed-phase products at the reaction temperature for a wide range of O/F ratios.

Original languageEnglish (US)
Pages (from-to)871-878
Number of pages8
JournalProceedings of the Combustion Institute
Issue number1
StatePublished - 2000
Event30th International Symposium on Combustion - Chicago, IL, United States
Duration: Jul 25 2004Jul 30 2004

All Science Journal Classification (ASJC) codes

  • General Chemical Engineering
  • Mechanical Engineering
  • Physical and Theoretical Chemistry


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