NUMERICAL STUDY OF THE INHIBITION OF PREMIXED AND DIFFUSION FLAMES BYIRON PENTACARBONYL

Iron pentacarbonyl (Fe(CO)(5)) is an extremely efficient flame inhibit or, yet its inhibition mechanism has not been described. The flame-inh ibition mechanism of Fe(CO)(5) in premixed and counterflow diffusion f lames of methane, oxygen, and nitrogen is investigated. A gas-phase in hibition mechanism involving catalytic removal of H atoms by iron-cont aining species is presented. For premixed flames, numerical prediction s of burning velocity are compared with experimental measurements at t hree equivalence ratios (0.9, 1.0, and 1.1) and three oxidizer composi tions (0.20, 0.21, and 0.24 oxygen mole fraction in nitrogen). For cou nterflow diffusion flames, numerical predictions of extinction Strain rate are compared with experimental results for addition of inhibitor to the air and fuel stream. The numerical predictions agree reasonably well with experimental measurements at low inhibitor mole fraction, b ut at higher Fe(CO)(5) mole fractions the simulations overpredict inhi bition. The overprediction is suggested to be due to condensation of i ron-containing compounds since calculated supersaturation ratios for F e and FeO are significantly higher than unity in some regions of the f lames. The results lead to the conclusion that inhibition occurs prima rily by homogeneous gas-phase chemistry. (C) 1998 by The Combustion In stitute