A skeletal mechanism for prediction of ignition delay times and laminar premixed flame velocities of hydrogen-methane mixtures under gas turbine conditions

Abstract

The aim of this study is to eliminate unimportant steps from a detailed chemical-kinetic mechanism in order to identify a skeletal kinetic mechanism that can predict with sufficient accuracy ignition delay times and laminar premixed-flame velocities for H2 - CH4 mixtures under conditions of practical interest in gas-turbine applications, which pertain to high pressure, high reactant temperature, and primarily lean-to-stoichiometric mixture compositions (although somewhat rich conditions also are considered for completeness). The accuracy of selected detailed chemical-kinetic mechanisms that are suited to represent combustion of hydrogen-methane mixtures in air was evaluated through comparison of computed and measured ignition delay times and laminar flame velocities, and because of its relative simplicity and sufficient accuracy, the San Diego mechanism was selected for the needed chemical-kinetic reduction. Under the pressure and temperature conditions of the mixture composition addressed, thirty nine reversible elementary steps involving eighteen species were found to suffice to describe with acceptable accuracy both the ignition delay time and the laminar burning velocities. The skeletal mechanism is given here, along with discussion of its derivation and characteristics, as well as comparison of its predictions with those of the detailed mechanism and, where possible, with experiment.