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Physical and Chemical Aspects of Cup-Burner Flame Extinguishment.


pdf icon Physical and Chemical Aspects of Cup-Burner Flame Extinguishment. (347 K)
Takahashi, F.; Linteris, G. T.; Katta, V. R.

Paper 21; HOTWC 2005;

Halon Options Technical Working Conference, 15th Proceedings. HOTWC 2005. Sponsored by: 3M Specialty Materials, Boeing, Chemical Development Studies, Inc., DuPont Fire Extinguishants, Halon Alternative Research Corp., Hughes Associates, Inc., Kidde-Fenwal, Inc., Sandia National Laboratories, SEVO Systems, Next Generation Fire Suppression Technology Program. May 24-26, 2005, Albuquerque, NM, 1-10 pp, 2005.

Keywords:

halon alternatives; halons; halon 1301; cup burners; flame extinguishment; diffusion flames; laminar flames; fire extinguishing agents; heat capacity; flame temperature; flame structure

Abstract:

Extinguishing limits of laminar methane-air co-flow diffusion flames in a cup-burner apparatus in normal earth gravity have been determined experimentally and computationally. A gaseous fire-extinguishing agent (Ar, He, N2, CO2, CF3H, CF3Br, or Br2) was added gradually into the coflowing oxidizer until the flame extinguished. The extinguishment of cup-burner flames, which resemble real fires, occurred via a blowoff process (in which the flame base oscillated before drifted downstream eventually) rather than the global extinction typical of counterflow diffusion flames. Unsteady numerical simulations with detailed chemistry revealed that the peak reactivity spot (i.e., reaction kernel), formed at the flame attachment point, was responsible for blowoff-type flame extinguishment. The complexity of chemical kinetics and dynamic flame-flow interactions associated with the blowoff process were treated accurately in the numerical model and the predictions for minimum extinguishing concentrations of various agents were in good agreement with the measurements.