Shock tube measurements of elementary oxidation and decomposition reactions important in combustion using hydroxide, methylidyne and nitrogen-carbon-nitrogen laser absorption

The kinetics of several elementary chemical reactions that are important in fuel-combustion and pollutant-formation have been studied using laser absorption spectroscopy and shock tubes.; OH concentration profiles and ignition delay times were measured in toluene-oxygen mixtures behind reflected shock waves. The reaction between toluene and OH, (1) C6H5CH3 + OH → Products, was found to be crucial to capturing the measured OH profiles. OH laser absorption at 306 nm was used to accurately determine k1. High-sensitivity measurements of OH were also used to study several important reactions in the formaldehyde system: (2) CH2O + OH → HCO + H2O, (3) CH 2O + Ar → Products, and (4) CH2O + O2 → HCO + HO2. The low-scatter measurements provide accurate kinetic data for modeling natural gas combustion and reliable targets for theory.; The two-channel thermal decomposition of methyl radicals in argon, (5a) CH3 + Ar → CH + H2 + Ar and (5b) CH3 + Ar → CH2 + H + Ar, was studied in high-temperature shock tube experiments using CH and OH laser absorption at 431 nm and 306 nm, respectively. CH radicals were generated by shock-heating dilute mixtures of ethane or methyl iodide in an argon bath, while OH was produced by shock-heating dilute mixtures of ethane or methyl iodide and excess O2 in argon. Detailed chemical kinetic mechanisms were used to model the measurements and infer k5a and k5b.; The prompt-NO initiation reaction, (7) CH + N2 → Products, was investigated behind reflected shock waves using CH and NCN laser absorption at 431 nm and 329 nm, respectively. The overall rate coefficient of the CH+N 2 reaction was measured using a CH perturbation approach. At high temperatures, there are two possible product channels for the reaction between CH and N 2, (7a) CH + N2 → HCN + N, and (7b) CH + N2 → H + NCN. The branching ratio of reaction (7) was determined by CH laser absorption in experiments in a nitrogen bath, and establishes NCN and H as the primary products of the CH+N2 reaction. NCN was also detected by laser absorption at 329 nm and was used to study the reaction between H and NCN.