Infrared emission spectroscopy in H2/F2 and CH4/F2 premixed flames

Abstract

AbstractThe infrared emission corresponding to the Δ v=1 transitions of the vibrationally excited HF (1 < =v< =3) has been recorded in rich premixed hydrogen‐fluorine and methanefluorine flames burning at various pressure (1.3–9 torr). The initial hydrogen and fluorine element content was identical in both CH4‐and H2‐ fluorine flames.The rational temperature profiles have been determined as well as in H2/F2 flames than in CH4/F2 ones. The analysis of the experimental data has put forward the occurrence of an equilibrated vibrational population relatively early in the burnt gases region of flames burning at pressures higher than 5 torr. From these evidences, profiles of the relative mole fractions of HF in its vibrationally excited states (1 < =v< =3) have been established in both series of flames. The absolute total concentrations of HF have been deduced by considering the Lewis number equals to one and therefore the absolute mole fraction profiles of the individual vibrationally excited HF (0 < =v< =3) have been determined.Besides the well‐known mechanism of the HF formation in H2/F2 systems it appears clearly that in CH4/F2 flames the final concentration of fluorocarbon derivatives are close to those of fluorhydric acid. This evidence indicates that in rich methane‐fluorine flames the reaction CH3 + F2 → CH2F + HF and subsequent reactions of CH2F are important in addition of the primary attack of methane CH4 + F → CH3 + HF and CH4 + F → CH3F + H.