Edinburgh Napier University

  The reactions contributing to the explosive time scale that characterises the autoignition of a homogeneous stoichiometric CH4/ air mixture are identified, using two different chemical kinetics mechanisms; the well known GRI-3 mechanism (53/ 325 species/ reactions with N-chemistry) and a mechanism developed recently (113/710 species/reactions without N-chemistry; Combustion and Flame 162 (2015) 315-330).Although the two mechanisms provide qualitatively similar results (regarding the ignition delay and the profiles of the temperature, of the mass fractions and of the explosive time scale), it is shown that the reactions responsible for the generation ofthe explosive time scale differ significantly. The present analysis aims in exploring the origin of the increasing accuracy provided by the kinetics mechanisms of increasing complexity.