The Structure of Laminar Diffusion Flames Inhibited with CF₃Br

Abstract

The paper presents a study of the chemical inhibition effects of CF₃Br (halon-1301) in laminar diffusion flames of CH₄-air and CO/H₂/N₂ fuels. Comparisons are made between measurements and computations for flames of pure fuel, fuel premixed with CF₃Br and for flames of pure fuel with the surrounding air premixed with CF₃Br. The measurements of temperature and the concentration of many stable species including HF, H Br and CF₃Br as well as the hydroxyl radical, OH are made in axisymmetric flames using the Raman-Rayleigh-LIF technique. Calculations are performed for laminar counterflow nonpremixed flames using complex chemistry and detailed transport properties. It is found that the addition of halon-1301 increases the peak temperature of the flame and causes little change in the concentrations of stable species. However, the minor species and flame radicals are significantly affected. The rate of decomposition of CF₃Br is not well predicted and significant discrepancy exists in the computations of halon related species. Unreliable chemical kinetic rates and experimental error particularly on HF and HBr appear to be the major contributing factors.

Key words:

• Laminar flames
• chemical inhibition
• halon
• laser diagnostics