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Combustion Inhibition and Enhancement of Cup-Burner Flames by CF3Br,C2HF5, C2HF3Cl2, and C3H2F3Br

Published

Author(s)

Gregory T. Linteris, F Takahashi, Viswanath R. Katta

Abstract

Numerical simulations of cup-burner flames in normal Earth gravity have been performed to study the combustion inhibition and unwanted enhancement by fire-extinguishing agents CF3Br (Halon 1301) and some potential replacements (C2HF5, C2HF3Cl2, and C3H2F3Br). A propane-ethanol-water mixture, prescribed for a Federal Aviation Administration (FAA) aerosol can explosion simulator test, was used as the fuel. The time-dependent, two-dimensional numerical code, which includes a detailed kinetic model (up to 241 species and 3918 reactions), diffusive transport, and a gray-gas radiation model, revealed unique two-zone flame structure and predicted the minimum extinguishing concentration of agent when added to the air stream. The general trend was similar to, but stronger than, that in microgravity flames studied previously (for two of the agents). The peak reactivity spot (i.e., reaction kernel) at the flame base stabilized a trailing flame in a buoyancy-induced entrainment flow. As the volume fraction of agent in the coflow (Xa) increased gradually: (1) the premixed-like reaction kernel weakened (but nonetheless formed at higher temperature and velocity); (2) the flame base detached from the burner rim and stabilized increasingly inwardly and higher above the burner rim, until finally, blowoff-type extinguishment occurred; (3) the calculated maximum flame temperature remained nearly constant ( 1800 K) or mildly increased; and (4) the total heat release of the entire flame decreased (inhibited) for CF3Br but increased (enhanced) for the halon replacements. In the trailing flame with C2HF5, a two-zone flame structure (with two heat- release-rate peaks) developed: in the inner zone, H2O (a product of hydrocarbon-O2 combustion and a fuel component) was converted further to HF and CF2O through exothermic reactions occurring in the outer zone, where exothermic reactions of the inhibitor also released heat; CO2 was formed in-between. Thus, addition of C2HF5 resulted in
Citation
Proceedings of the Combustion Institute
Volume
35

Keywords

Aircraft cargo-bay fire suppression, Halon 1301 replacement, HFC-125, HCFC-123, 2-BTP

Citation

Linteris, G. , Takahashi, F. and Katta, V. (2015), Combustion Inhibition and Enhancement of Cup-Burner Flames by CF3Br,C2HF5, C2HF3Cl2, and C3H2F3Br, Proceedings of the Combustion Institute, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915205 (Accessed April 13, 2024)
Created March 13, 2015, Updated February 19, 2017