Cup-Burner Flame Structure and Extinguishment by C2HF5 in Microgravity

Published

September 26, 2012

Author(s)

Gregory T. Linteris, Fumiaki Takahashi, Viswanath R. Katta, Oliver Meier

Abstract

The effects of fire-extinguishing agent C2HF5 (pentafluoroethane, HFC-125) added to a coflowing airstream on the structure and extinguishing processes of microgravity cup-burner flames have been studied numerically. Propane and a propane-ethanol-water fuel mixture, prescribed for a Federal Aviation Administration (FAA) aerosol can explosion simulator test, were used as the fuel. The time-dependent, two-dimensional numerical code, which includes a detailed kinetic model (177 species and 2986 reactions), diffusive transport, and a gray-gas radiation model, revealed unique flame structure and predicted the minimum extinguishing concentration of agent. The peak reactivity spot (i.e., reaction kernel) at the flame base stabilized a trailing flame. The calculated flame temperature along the trailing flame decreased downstream due to radiative cooling, causing local extinction at 0.08), parallel to the axis until finally blowoff-type extinguishment occurred; (2) the reaction kernel weakened (i.e., lower heat release rate) but nonetheless formed at higher temperature; (3) the calculated maximum flame temperature remained at nearly constant ( 1700 K); and (4) the total heat release of the entire flame increased (i.e., combustion enhancement). In the lifted flame base, H2O formed from hydrocarbon-O2 combustion was converted further to HF and CF2O through exothermic reactions, thus resulting in a heat-release rate peak. In the trailing flame, two-zone flame structure developed: CO2 and CF2O were formed primarily in the inner and outer zones, respectively, while HF was formed in both zones. As a result, the combustion enhancement due to the C2HF5 addition occurred primarily in the trailing flame.

Citation

Proceedings of the Combustion Institute

Volume

34

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.proci.2012.06.091

Keywords

Aircraft cargo-bay fire suppression, Halon replacement, Diffusion flame stabilization, Reaction kernel, Microgravity combustion

Citation

Linteris, G. , Takahashi, F. , Katta, V. and Meier, O. (2012), Cup-Burner Flame Structure and Extinguishment by C2HF5 in Microgravity, Proceedings of the Combustion Institute, [online], https://doi.org/10.1016/j.proci.2012.06.091 (Accessed December 13, 2024)