Numerical Study on Ignition Characteristics of Methane-air Mixture Using Detailed Chemical Kinetics

Abstract

Ignition is a transient combustion phenomenon and one of the most difficult and complex problems, which include a lot of physical and chemical processes, so that it has not yet been explained suficiently. In the present study, the ignition characteristics of methane-air mixture were investigated by numerical analysis using detailed chemical kinetics. In order to clarify the effect of geometric condition of ignition source and flow field on ignition characteristics, ignition processes for 1-D plane model, 2-D plane model and axisymmetric model were examined comparatively. The following conclusions were reached : (1) Ignition characteristics are better for the case where the heat is hard to radiate to surrounding fluid, but the reaction mechanism of ignition is almost the same. (2) The elementary reactions, which are important at the moment of ignition, are as follows : CH3 + O →CH2O + H, CH3 + O → CO + H + H2, and H + O2 → O + OH. (3) The success and failure of ignition andthe ignition delay depend on the supplying manners of ignition energy, especially heating time and ignition source shape.