The methyl nitrite decomposition flame

Abstract

Laser-induced fluorescence (LIF) and emission spectroscopies are used for the characterization of species and temperature in premixed, laminar, flat flames of CH4/NO2/O2 at 55 torr. Relative concentration profiles are obtained for the following species—OH, CH, NO, NO2, and CN. Temperatures are measured by rotational analysis of OH radical LIF excitation spectra and yield a peak temperature of ≈ 2400 K. Chemical kinetic modeling of a 252-reaction, 54-species mechanism is performed using the Sandia Chemkin-II/Premix flame codes in order to obtain mechanistic information. This flame exhibits a two-emission zone structure: an orange/yellow emission due to NO2 chemiluminescence, and a violet zone due to emission from OH, CH, NO, NO2, CN, and NH. The LIF profiles demonstrate rapid removal of NO2 and its conversion to NO. The CH profile is complicated by interference from laser photolytic perturbation of the flame and NO2 anti-Stokes fluorescence. The OH profile exhibits a double peak structure that is not reproduced by the kinetic modeling. The modeling result predicts that each of the species profiles occurs further from the burner than experimentally measured. It is proposed that this is due to the lack of high-temperature kinetic data for reactions of NO2 with hydrocarbon species. Analysis of the modeling result is performed to determine the reactions that are most important. Sensitivity analysis is performed to demonstrate the sensitivity of species mole fractions to changes in rate parameters.