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Extinguishment and Enhancement of Propane Cup-Burner Flames by Halon and Alternative Agents

Published

Author(s)

Gregory T. Linteris, Fumiaki Takahashi, Viswanath R. Katta, Valeri I. Babushok

Abstract

Computations of cup-burner flames in normal gravity have been performed to reveal the combustion inhibition and enhancement by the CF3Br (halon 1301) and potential alternative fire-extinguishing agents (C2HF5, C2HF3Cl2, and C3H2F3Br). 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, reveales unique two-zone flame structure. For propane, general trends in the structure are similar to those of the fuel mixture. The peak reactivity spot (i.e., reaction kernel) at the flame base stabilizes a trailing flame, which is inclined inwardly by a buoyancy-induced entrainment flow. As the volume fraction of agent in the coflow increases gradually, the premixed-like reaction kernel weakens, thus inducing the flame base detachment from the burner rim and blowoff-type extinguishment eventually. The H2O in the inner zone, is converted further, primarily in the outer zone, to HF and CF2O through exothermic reactions most significantly with the C2HF5 addition. Despite endothermic decomposition of the agent, exothermic reactions of the inhibitor fragments also contribute to the heat-release rate in the outer zone. Although the rates of formation (and associated heat-release rates) of HF and CF2O are lower for propane, compared to the fuel mixture, two heat-release-rate peaks in the two-zone flame structure in the trailing flame are comparable for both fuels. A main heat-release step to form CO2 in the hydrocarbon-O2 combustion takes place in-between the two zones. The total heat release of the entire flame decreases (inhibiting) for CF3Br but increases (enhancing) for the halon alternative agents, particularly C2HF5 and C2HF3Cl2. Addition of C2HF5 resultes in unusual (non-chain branching) reactions and increases total heat release (combustion enhancement)primarily in the trailing diffusion flame.
Proceedings Title
Proc. of the Eighth International Seminar on Fire & Explosion Hazards (ISFEH8),
Conference Dates
April 25-28, 2016
Conference Location
Hefei, CN
Conference Title
Eighth International Seminar on Fire & Explosion Hazards (ISFEH8),

Keywords

Aircraft cargo-bay fire suppression, Diffusion flame stabilization, Halon 1301 replacement, Reaction kernel.

Citation

Linteris, G. , Takahashi, F. , Katta, V. and Babushok, V. (2016), Extinguishment and Enhancement of Propane Cup-Burner Flames by Halon and Alternative Agents, Proc. of the Eighth International Seminar on Fire & Explosion Hazards (ISFEH8),, Hefei, CN, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=920672 (Accessed March 2, 2024)
Created September 20, 2016, Updated April 4, 2022