John F. Papp

Molecular beam mass spectrometry applied to determining the kinetics of reactions in flames. I. Empirical characterization of flame perturbation by molecular beam sampling probes

Several types of quartz sampling probes, designed to sample directly both stable and unstable species from low-pressure flames, have been empirically characterized relative to the conventional quartz microprobes. Comparison has been made with respect to visual perturbation of the flame, stable species concentration profiles, temperature profiles, and sensitivity to radicals. It is concluded that if care is taken to obtain the correct geometry just at the probe tip, then it is not unreasonable to expect to obtain flame structure data of sufficient quality to permit quantitative analyses for reaction rates.

Concentration profiles for radical species in a methane-oxygen-argon flame

Concentration profiles through the reaction zone of a low-pressure, slightly rean methane-oxygenargon flame have been measured, in situ , for the following unstable species: oxygen atoms, hydrogen atoms, hydroxyl radicals, methyl radicals, and formyl radicals. The conditions of measurement, means of identification, and method for estimating the concentrations of the radicals are described. The observed maximum mole fractions are 2.3 × 10 −2 for H, 1.1 × 10 −2 for OH, and 0.8 × 10 −2 for O, the maxima occurring in the recombination zone for these species. The maximum values are in excess of equilibrium concentration by factors of ∼10−10 3 . Methyl and formyl radicals have maximum mole fractions in the reaction zone of 2.2 × 10 −3 and 6 × 10 −5 , respectively. Equilibrium constants, calculated from the appropriate measured species concentrations for the fastest reactions of the H 2 CO O 2 flame, which is the last stage of this hydrocarbon flame, suggests that these reactions are essentially balanced in this part of the flame.