Laminar flame propagation in supercritical hydrogen/air and methane/air mixtures

The laminar propagation of hydrogen/air and methane/air flames in supercritical conditions was computationally simulated for the planar configuration, incorporating descriptions of supercritical thermodynamics and transport as well as high-pressure chemical kinetics. The inaccuracies associated with the use of the ideal gas assumptions for various components of the supercritical description were systematically assessed with progressively more complete formulation. Specifically, for hydrogen/air flames, the laminar flame speeds at high pressures were found to increase with the use of the non-ideal equation of state (EoS), and is mainly due to the density modification of the initial mixture. Including the thermodynamic properties of enthalpy and heat capacity reduces the flame speed because of the correspondingly reduced adiabatic flame temperature. Diffusive transport properties were found to have small effect because of the inherent insensitivity of the laminar burning rate to their variations. For methane/air flames, the use of recently reported high-pressure chemical kinetics considerably affects the laminar flame speed, even for the same flame temperature.