Spectroscopic Investigation of Atmospheric-Pressure Counterflow Diffusion Flames Inhibited by Halons

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Abstract
Infrared spectra of atmospheric-pressure counterflow diffusion flames inhibited by halons (a contraction of halogenated hydrocarbons) and a few of their potential replacements are measured with the use of Fourier transform spectroscopy. Results are compared to spectra of similar flame systems examined at low pressure. It is shown that, for atmospheric-pressure counterflow diffusion methane/air flames inhibited by CF3Br, CF2H2, and CF4, the two major fluorine-containing combustion products are HF and CF2O. A correlation is shown between flame inhibition efficiency and CF2O formation for atmospheric-pressure counterflow diffusion flames inhibited by these halons. For low-pressure premixed flames inhibited by CF3Br, HF appears to be the only fluorine-containing combustion product, even at relative dopant levels 15 times higher than those capable of extinguishing atmospheric-pressure counterflow diffusion flames. The results of these experiments illustrate the need for flame inhibitant testing over a wide spectrum of flame conditions, while providing further evidence that, for atmospheric-pressure inhibition of real fires by halons, CF2O may be a good indicator of inhibitor efficiency when that inhibition is at least partly accomplished by chemical scavenging of reactive combustion intermediates.