Numerical Study on the Kinetic Effects of Hydrogen Addition on the Thermal Characteristics of Laminar Methane Diffusion Flames

Abstract

Abstract The kinetic effects of H2 addition on the thermal characteristics of laminar methane diffusion flames were numerically studied using a detailed chemical kinetics consisting of 53 species and 325 reactions. The variations in the heat release properties and relevant key reactions with H2 addition were analyzed. Results show that the reactions of H + O2 + H2O ⇔ HO2 + H2O (R35), H + HO2 ⇔ OH + OH (R46), H + CH3 (+ M) ⇔ CH4 (+ M) (R52) and OH + H2 ⇔ H + H2O (R84) present important roles in the global heat release and the contributions of these reactions significantly increased as H2 is added to CH4 stream. Moreover, the increase rate of contribution of R84 with H2 addition is much larger than those of the reactions of R35, R46 and R52. The H and OH are the two most important radicals for heat release in the combustion process of CH4-H2 diffusion flame. The reaction of R84 is one of the main contributors for production of H radical and the contribution of R84 significantly increased with H2 addition, while the reaction of H + O2 ⇔ O + OH (R38) dominates the contribution of production of OH, which contributes more than 50 %, no matter whether H2 is added to CH4 stream.