(563b) The Influence of Ammonia on Flame Characteristics and Soot Formation in Ammonia/Methane Diffusion Flames

Because of narrow stability limits for the efficient burning of ammonia (NH₃), strategies for enhancing the stability of NH₃ combustion processes have been pursued, such as through co-firing with hydrocarbons. Under these circumstances soot formation becomes possible, and the influence of NH₃ on soot emissions in these technologies becomes relevant. However, there is a lack of studies that have analyzed the effect of NH₃ on soot formation pathways and how it ultimately impacts particulate matter emissions. In order to begin answering these questions, we measured the flame structure characteristics and relative soot volume fraction distributions in NH₃-CH₄ co-flow diffusion flames with varying levels of NH₃-blending. We also compared these measurements to those in N₂-diluted CH₄ flames for reference. Center-line temperature measurements and flame images were taken to determine flame heights and lift-off heights, respectively, and relative maximum soot volume fractions in flames with varying ratios of NH₃ and CH₄ were measured using line-of-sight spectral radiance. Computational 2D flame simulations were also employed in order to estimate flame lengths, lift-off heights, and distributions of species relevant to soot formation. Experimental and computations results are compared against each other in order to assess the accuracy of the underlying chemical mechanism and begin explaining the soot formation pathways affected by the presence of NH₃.