Coupling effects of hydrogen transport and reactivity on NO production in laminar nonpremixed methane/air flames

A computational simulation of counterflow nonpremixed flame was performed to study the effects of hydrogen enrichment on NO chemistry on the basis of the methodology of fabricating hydrogen enrichment. Normal hydrogen and the fictitious hydrogen enrichment with weakened transport properties were both introduced into flame modeling and the comparative analysis was implemented to explore the coupling effects of the physical transport and reactivity of hydrogen enrichment on NO production. The study focused on the variations in NO peak concentration and the total production rate of NO versus hydrogen enrichment rate. The contributions and sensitivities of key reactions to NO production were estimated to determine the influencing routes of hydrogen enrichment on NO chemistry. The flame structures were compared in terms of the convection, conduction, diffusion and reaction in flame energy and hydrogen species conservations. The coupling interaction between hydrogen diffusion and the reaction promotion caused by hydrogen diffusion is the dominant kinetic incentive of hydrogen enrichment on NO production in nonpremixed methane/air flames.