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

The kinetic effects of H-2 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 H-2 addition were analyzed. Results show that the reactions of H + O-2 + H2O double left right arrow HO2 + H2O (R35), H + HO2 double left right arrow OH + OH (R46), H + CH3 (+ M) double left right arrow CH4 (+ M) (R52) and OH + H-2 double left right arrow H + H2O (R84) present important roles in the global heat release and the contributions of these reactions significantly increased as H-2 is added to CH4 stream. Moreover, the increase rate of contribution of R84 with H-2 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-H-2 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 H(2 )addition, while the reaction of H + O-2 double left right arrow O + OH (R38) dominates the contribution of production of OH, which contributes more than 50 %, no matter whether H-2 is added to CH4 stream.