Analysis of Excited Species Formation across the Flame of Various Ammonia-Hydrogen Fired Combustor Geometries

Abstract

Although ammonia can be used as a fuel, it also presents drawbacks that require further investigation before the chemical can overtake fossil fuels in combustion systems. The main barriers are the low flammability in combination with high NOx emissions. Although the first barrier can be surpassed by doping ammonia with hydrogen, the second becomes more challenging under these conditions, as hydrogen increases NO emissions due to the increase in H radicals in the chemical pool of species. How the change in radicals impacts the stability of the flame, its reactivity, and emissions profile is of the greatest concern for the use of these net zero fuels. Thus, the work herein presented shows the trends of excited species such as NH*, NH₂*, and OH* when using ammonia–hydrogen at 70%–30% (vol) blending. Various equivalence ratios are employed from lean to rich conditions. Results denote that there is a continuous displacement of radicals across the field, with NH₂* relocating closer to the centerline of the burner as equivalence ratio increases, while NH* tends to raise its location while dislocating from the production/consumption of OH* radicals. The results can be used to target desirable radicals for the mitigation of emissions and flame control.