Structure of premixed H2/O2/Ar flames at 1–5 atm studied by molecular beam mass spectrometry and numerical simulation

Abstract

A lack of available experimental data for spatial distributions of the species mole fractions in the flames of hydrogen at the pressures higher than atmospheric, which are required for developing and validating reliable kinetic models for hydrogen combustion, motivated this study. Stoichiometric laminar premixed H2/O2/Ar flames stabilized on flat burners at pressures 1, 3 and 5atm were examined in this work by molecular beam mass spectrometry. Mole fraction profiles of all flame species (H2, O2, H2O, H2O2, H, O, OH, HO2) were measured. A decrease in the peak mole fractions of H, O, OH radicals and an increase in the peak mole fractions of HO2 and H2O2 with pressure was observed. Two detailed kinetic mechanisms proposed recently by Konnov (2008) and Burke et al. (2012) for hydrogen combustion were validated against new experimental data reported in this work. Both mechanisms reproduced well the mole fraction profiles of H2, O2, H2O and H, O, OH radicals in the flames. However, the mechanism of Burke et al. was found to be more adequate in predicting the mole fraction profiles of peroxy species in the flames. The observed changes in the flame structure with pressure were explained on the basis of a kinetic analysis of the model developed by Burke et al. The experimental data reported in this work can help in further development and improvement of the future kinetic models of hydrogen combustion at elevated pressures.