Measurements and modelling of nitrogen species in CH4/O2/N2 flames doped with NO, NH3, or NH3+NO

Abstract Species profiles measurements were performed by using Molecular Beam Mass Spectrometry in low pressure CH 4 /O 2 /N 2 flames doped with NO, NH 3 or NH 3 +NO. The present paper aims to study NO/NH 3 conversion in hydrocarbon flames. It is based on the analysis of CH 2 /CH 3 radicals and NO, NH 3 and HCN species profiles. In NO doped flame, NO-reburning prevails, but in NH 3 and NH 3 +NO doped flames, NH 3 conversion in NO was measured with a yield close to 90–100%. HCN peak mole fractions were found in similar amount in the NH 3 and NH 3 +NO doped flames, twice higher than in the NO doped flame. Experimental results are compared to simulated species profiles by using three detailed mechanisms. A general good agreement between experimental and simulated NO and NH 3 profiles is observed. However, simulated HCN peak mole fractions overpredict the experimental ones. Reaction pathways analysis performed by using detailed mechanisms reveals that the HCN formation is due to NO-reburning reactions and to reactions from the NH 3 subset (via H 2 CN and HNCN). According to the mechanism from Tian et al. (2009), the importance of NH 3 subset prevails in NH 3 and NO+NH 3 doped flames.