An experimental and kinetic modeling study of premixed NH 3/CH 4/O 2/Ar flames at low pressure

Abstract

An experimental and modeling study of 11 premixed NH 3/CH 4/O 2/Ar flames at low pressure (4.0 kPa) with the same equivalence ratio of 1.0 is reported. Combustion intermediates and products are identified using tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry. Mole fraction profiles of the flame species including reactants, intermediates and products are determined by scanning burner position at some selected photon energies near ionization thresholds. Temperature profiles are measured by a Pt/Pt–13%Rh thermocouple. A comprehensive kinetic mechanism has been proposed. On the basis of the new observations, some intermediates are introduced. The flames with different mole ratios ( R) of NH 3/CH 4 ( R0.0, R0.1, R0.5, R0.9 and R1.0) are modeled using an updated detailed reaction mechanism for oxidation of CH 4/NH 3 mixtures. With R increasing, the reaction zone is widened, and the mole fractions of H 2O, NO and N 2 increase while those of H 2, CO, CO 2 and NO 2 have reverse tendencies. The structural features by the modeling results are in good agreement with experimental measurements. Sensitivity and flow rate analyses have been performed to determine the main reaction pathways of CH 4 and NH 3 oxidation and their mutual interaction.