Experimental and kinetic studies on laminar burning velocity of NH₃/N₂O/N₂ and CH₄/N₂O/N₂ mixtures under sub-atmospheric and elevated pressures

New experimental data on laminar burning velocities (LBVs) of NH₃/N₂O/N₂ and CH₄/N₂O/N₂ mixtures under sub-atmospheric (0.75 bar) and elevated pressures (1.5 bar) across a wide range of equivalence ratios (ϕ = 0.6–1.8) were obtained using a constant volume combustion chamber. A modified CEU-1.2 kinetic model based on the present data and other types of data has been updated. The results indicate that the flame propagation velocities of NH₃/N₂O flames are generally ten times higher than those of NH₃/air flames and three times higher than those of NH₃/O₂/N₂ mixtures with similar O: N mole ratios. Eight models were adopted for simulation, and it was found that the CEU-1.2 model and the Zou model perform best in reproducing the experimental results. The measured Markstein length suggests that N₂O can increase the Markstein length on the fuel-lean side compared to NH₃/air mixtures. The simulation results show that the increase in flame temperature plays a dominant role in enhancing flame speed and NO formation in NH₃/N₂O flames compared to NH₃/O₂/N₂ flames. While under the similar flame temperature, the LBV is lower in N₂O flames than O₂/N₂ flames due to the decreased OH radical especially at fuel-lean side. NO concentration and laminar flame speed are both insensitive to pressure variation for N₂O flames. The LBV data of NH₃/N₂O/N₂ and CH₄/N₂O/N₂ mixtures in this work can provide highly sensitive validation targets for the kinetics of hydrocarbon, ammonia, and N₂O interactions.