Study of the H + O + M reaction forming OH∗: Kinetics of OH∗ chemiluminescence in hydrogen combustion systems

The temporal variation of OH∗ (A2Σ+) chemiluminescence in hydrogen oxidation chemistry has been studied in a shock tube behind reflected shock waves at temperatures of 1400–3300 K and at a pressure of 1 bar. The aim of the present work is to obtain a validated reaction scheme to describe OH∗ formation in the H2/O2 system. Temporal OH∗ emission profiles and ignition delay times for lean and stoichiometric H2/O2 mixtures diluted in 97–98% argon were obtained from the shock-tube experiments. Based on a literature review for the hydrogen combustion system, the key reaction considered was H + O + M = OH∗ + M (R1). The temperature dependence of the measured peak OH∗ emission from the shock tube and the peak OH∗ concentration from a homogeneous closed reactor model are compared. Based on these results a reaction rate coefficient of k1 = (1.5 ± 0.4) × 1013 exp(−25 kJ mol−1/RT) cm6 mol−2 s−1 was found for the forward reaction (R1) which is slightly higher than the rate coefficient suggested by Hidaka et al. (1982). The comparison of measured and simulated absolute concentrations shows good agreement. Additionally, a one-dimensional laminar premixed low-pressure flame calculation was performed for where absolute OH∗ concentration measurements have been reported by Smith et al. (2005). The absolute peak OH∗ concentration is fairly well reproduced if the above mentioned rate coefficient is used in the simulation.