Interactions of premixed flames with surfaces: Flame stability and pollutant abatement
Thermal and chemical interactions of premixed flames with inert and catalytic surfaces are studied in this dissertation, for the purpose of elucidating their effects on flame stability and pollutant emissions. Both weak chemical flame-surface coupling (due to radical wall recombination) and strong chemical coupling (due to catalytic wall activity), have been analyzed. A combination of model development and analysis has been used to comprehend various experimentally observed phenomenon, ranging from the effect of surface phenomenon on NO x and fuel emissions.
Detailed model analysis has been undertaken in order to determine the effects of thermal and radical wall quenching on bifurcation behavior, wall heat flux, and pollutant emissions, in premixed hydrogen and methane/air flames. A new method to identify the contributions of various NO formation pathways (e.g., the Zeldovich, NNH, and prompt NOx pathways), has been developed.
A new methodology for the construction of thermodynamically consistent, detailed surface reaction mechanisms has been developed. The energetics of the reaction mechanisms are derived from the application of the unity bond index-quadratic exponential potential (UBI-QEP) formalism, with species coverage dependent heats of adsorption, obtained from experiments or theory, as an input. Transition state theory estimates are used initially for the pre-exponentials of the reactions, while experimental data is used the sticking probabilities. Large scale simulations are then conducted using this reaction mechanism coupled with appropriate gas-phase chemistry and reactor scale models, to obtain predictions of targeted experiments. Reaction path analysis and sensitivity analysis are employed to identify the important steps for each experiment. A mathematical optimization of the important pre-exponentials against the targeted experiments is then undertaken, by, and refine the pre-exponentials of these reactions. Finally, this optimized mechanism is validated by comparison with other sets of experiments. Detailed reaction mechanisms for H2, CO, and CH 4/air mixtures over platinum are developed.
0768: Environmental science