Application of tunable diode laser diagnostics for temperature and species concentration profiles of inhibited low-pressure flames.

We have employed tunable diode laser absorption spectroscopy (TDLAS) to characterize low-pressure premixed CH4/O2/Ar flames inhibited with Halon 1301 (CF3Br) and the candidate Halon alternative compounds FE-13 (CF3H) and HFC-125 (C2F5H). This work is part of a larger program designed to help identify replacement fire-suppression compounds for the currently used Halon 1301. We have used CO two-line thermometry to profile the temperature in low-pressure laminar flames and have determined concentration profiles for a large number of flame species, including reactive intermediates. To date, we have detected 12 flame species by using TDLAS in our laboratory and report on seven of them here: CH4, H2O, CO, CF2O, CF2H2, CF3H, and CF4. To the best of our knowledge, this is the first time the last four species have been observed in flame by the use of TDLAS. Our data are important for validating the detailed kinetic mechanisms of chemical flame inhibition. Our results indicate that TDLAS is a versatile and powerful diagnostic technique for studying combustion processes.