Nitric oxide formation in flames of NH3/DME binary mixtures: Laser-induced fluorescence measurements and detailed kinetic analysis

Binary mixture of ammonia (NH₃) and dimethyl ether (DME) has been considered in literature as a potential fuel for practical use. Nitric oxide (NO) is a major product of combustion of NH₃-containing fuels, and its formation routes have to be comprehensively studied. In this work, concentration profiles of NO were experimentally measured in laminar axisymmetric flames using planar laser-induced fluorescence. The molar percentage of NH₃ in the NH₃/DME fuel mixture varied from 10% to 60%. Emission levels of NO have reached as much as around 1% for mixtures with around 50% NH₃. NO formation was analyzed with numerical simulations of 1D laminar flames and several detailed kinetic mechanisms. Modeling was performed in Chemkin with the steady-state burner-stabilized and free-propagating planar laminar flame reactor models. It was observed that the most recent versions of the contemporary NH₃/DME models are able to reproduce the experiments, and their predictions agree with each other due to similarities in the NH₃ submechanisms. Kinetic analysis has revealed some disagreement was observed in terms of how much direct chemical coupling between carbon- and nitrogen-containing species affects NO formation.