An Investigation of the Suppression Mechanism of CF_3Br Using the Reduced Kinetic Mechanisms for Premixed Hydrogen-Air-CF_3Br Flames

摘要

The effectiveness of Halon 1301 (CF_3Br) in flame inhibition was investigated by studying the premixed H_2-Air flame using a simplified mechanism based on the original NIST CF_3Br mechanism. The simplified mechanism was capable of reproducing the detailed flame structure of the full mechanism including the flame temperature, burning velocity and species concentrations. The reaction rates of two crucial elementary reactions in the CF_3Br chemistry were then revised based on the recent theoretical considerations and were optimized with the existing measurements. The resulting simplified mechanism consisted of 28 elementary reactions and was capable of reproducing the measured unstretched laminar burning velocities of the premixed H_2-Air-CF_3Br flames for a wide range of fuel equivalence ratios and up to 2% of CF_3Br addition. The new mechanism also showed that there were two separate pathways in H atom abstraction due to CF_3Br addition: the initial low temperature scavenging of H by CF_3Br, and the catalytic destruction of H atoms through HBr+H=Br+H_2 and Br+H+M=HBr+M in the main flame zone. The simplified mechanism was further reduced to a five-step global mechanism that was able to retain the accuracy of the detailed mechanism.