Reaction Mechanisms in Hydrogen-Nitric Oxide Flames

Abstract

Atmospheric, premixed, flat H2-NO flames have been stabilized on a 3.5 cm diameter, Meker type burner in the temperature range of 2800-3100° K. Temperature profiles and concentration profiles of NO, OH and O were determined in the reaction and post-reaction zones using exclusively spectrophotometric techniques. These data in conjunction with the OH emission profiles were used to analyse the reaction mechanisms occurring in the flame. OH radiation was found to be of chemiluminescent origin according to a thermo-molecular recombination reaction: possibly H + OH + OH→ H2O+ OH* or O + Ha + OH * HaO + OH* NO decomposition appears to be rate controlled by two reactions: H + NO → N + OH (1) and O 4- NO → N + O2 (2r. Reaction (1) is more important in the early stage of combustion due to diffusion of H atoms from the reaction zone. Later the concentration of O atoms builds up and reaction (2) becomes significant. The rate constant for reaction (1) was determined using the flame data and was found to be: k₁= 2.3 × 10¹⁰ cm³/ mole-sec at 3000° K.