Experimental and Kinetic Study on OH* and CH* Chemiluminescence of Methane Oxidation at High Temperature behind...

Chemiluminescence, as an effective diagnostic method, is often used to study the flame structure, heat release, and equivalence ratio, which are significantly important for describing the complex combustion process. In this work, the time histories of chemiluminescence emission from OH*(A²Σ⁺) and CH*(A²Δ) in reacting methane/oxygen/argon mixtures have been simultaneously measured behind reflected shock waves. Experiments were conducted at pressures around 1.0 and 2.0 atm, equivalence ratios of 0.5 and 1.0, a fuel concentration of 0.2%, and temperatures ranging from approximately 1725 to 2743 K. Based on the measured OH* chemiluminescence time histories, the rate constant of reaction CH + O₂ ⇒ OH* + CO was determined to be 9.24 × 10¹⁵ × T^-0.4 exp(-4150 cal·mol^-1/RT) cm³ mol^-1 s^-1. A methane combustion mechanism involving the OH* and CH* reaction kinetics was constructed. The reliability of the constructed kinetic mechanism was verified by using the experimental kinetic data of OH* and CH* chemiluminescence, including the time histories and relative peak intensities.