ON THE ROLE OF TRANSPORT IN THE COMBUSTION KINETICS OF A STEADY-STATEPREMIXED LAMINAR CO+H2+O2 FLAME

The role of mechanistic steps, diffusion, and their interrelation is e xplored in a steady-state premixed laminar CO + H-2 + O2 flame using a numerical model. Sensitivity coefficients and Green's functions calcu lated for this system offer systematic characterization of the role of diffusion and exothermicity in carbon monoxide oxidation kinetics. Th e results reveal that the uncertainties in transport parameters are as important to the model predictions as those in the kinetic steps. The rate controlling steps of the CO + H-2 + O2 reaction are found to be different for adiabatic and nonadiabatic premixed flames, and also for systems with and without transport. In particular, the reactions of t he hydroperoxyl radical with hydrogen, oxygen, and hydroxyl radicals a re found to be important at all temperatures in the fuel lean (40 torr ) adiabatic flame studied here. The diffusive mixing of chemical speci es from the low and the high temperature portions of the flame and the larger heats of reaction associated with the hydroperoxyl radicals ar e found to be responsible for the increased importance of these reacti ons. (C) 1994 John Wiley & Sons, Inc.