Interaction of ammonia with nitric oxide and nitrous oxide: Multi-species time-history measurements and comprehensive kinetic modeling

Abstract

Interaction chemistry of ammonia and nitrogen oxides (NOx and N₂O) was investigated with the help of laser-based multi-species measurements in a shock tube. Mid-infrared laser diagnostics were set up to measure the time-histories of NH₃, NO, N₂O and H₂O in shock-heated NH₃/NO/Ar and NH₃/N₂O/Ar mixtures over temperatures of 1418–2381 K and pressures of 1.10–1.90 bar. A comprehensive H/N/O nitrogenous combustion model was formulated and validated with our experimental data, as well as a wide array of literature data encompassing various NH₃-NOx systems and other nitrogenous systems over temperatures of 425–2455 K, pressures of 0.8–100 bar, and equivalence ratios of 0.23–2.7. In the NH₃-NO system, the reactions NH₂+NO=N₂+H₂O and NH₂+NO=NNH+OH dominate NH₃ consumption and NO reduction, while NH+NO=N₂O+H governs N₂O formation. Sensitivity analysis of the branching ratio of NH₂+NO→NNH+OH and NH₂+NO→N₂+H₂O highlighted the significance of the proposed rate values in improving model performance, particularly at temperatures below 1800 K. In the NH₃-N₂O system, the kinetics of NH₂+N₂O, NH+N₂O and NH₃/NH₂/NH+O were identified as critical targets for kinetic modeling. Experimental and kinetic analysis revealed a three-stage NO reduction phenomena in NH₃-NO system, with effective NO reduction occurring over a narrow temperature range of 1400–1600 K and residence times ranging 1 to 700 ms. In the NH₃-N₂O system, nearly 90 % nitrogen oxides reduction was observed over 1075–1600 K and residence times of <1 s. These findings provide valuable insights for optimizing ammonia-fueled combustion systems to minimize nitrogen oxide emissions.