Influence of Steam and Elevated Ambient Conditions on N2O in a Premixed Swirling NH3/H2 Flame

Renewably generated NH3 has the potential to support future energy demand, however combustor designs and strategies require considerable development to ensure reduced NOx emissions. Expanding on previous work, a turbulent swirl burner was used to appraise potential NOx reduction pathways, both experimentally and numerically, with a premixed NH3/H2/air flame. With a 100-year global warming potential ∼265 times that of CO2, particular emphasis was given to N2O. Maintaining a constant thermal power, reactants were supplied at elevated temperature, with parametric changes made to pressure and humidity. Favourable agreement was demonstrated between exhaust emission measurements and simulations performed using a chemical reactor network model. NO and N2O emissions were shown to be sensitive to operational equivalence ratio, increasing by several orders of magnitude across the experimental range. An increase in combustor pressure was experimentally shown to reduce exhaust N2O concentrations with this globally lean fuel mixture, alongside NO. Steam injection was also explored in detail for the first time and shown to provide contrasting trends, with a reduction in NO, and a rise in N2O, as water loading was increased. Both pressure increase and steam injection were combined to give optimal NOx performance for the evaluated dataset. Changes in chemical kinetic pathways were investigated in detail, and compared to high-speed OH*, NH2*, and NH* chemiluminescence.