Simulation of high-pressure methane-oxygen combustion with a new reduced chemical mechanism

The modeling and simulation of methane-oxygen combustion at high pressure requires a dedicated kinetic mechanism to obtain a precise description of the fuel decomposition. However, using the detailed mechanisms literature in high-fidelity simulations, like direct numerical simulations, is not possible due to the high numerical cost. Accordingly, a reduced chemical mechanism is required, and the one proposed in this study contains 17 species and 44 reactions to encompass a very large range of pressure (P is an element of [1, 100] bar) and equivalence ratio (phi is an element of [0.2, 14]). The Optimized and Reduced Chemistry method, that is based on directed relation graph with error propagation, is applied to the RAMEC kinetic scheme, and validations are performed for a set of canonical test-cases: auto-ignition delay simulation, one-dimensional laminar premixed flame freely propagating and one-dimensional counterflow diffusion flame. A very good agreement is obtained by comparison with the RAMEC detailed mechanism. To further evaluate the ability of the reduced mechanism, a premixed flame expanding in a homogeneous isotropic turbulence at high pressure (P = 56 bar) is performed. The temporal evolution of the flame front is detailed from its ignition, revealing the flame behavior and its interaction with turbulence. The new reduced chemical mechanism performs well with a relative error of 4% for the maximum of temperature at each time step and even less if the difference observed in the auto-ignition times between the two mechanisms is considered. Finally, a substantial gain is found when using the reduced scheme on three-dimensional cases, the simulations being 8 times faster than those using the detailed scheme. A dedicated post-processing tool based on the contour tracing labeling method is developed to measure the flame length. (C) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.