Reduced Chemical Kinetic Mechanisms for Oxy/Methane Supercritical CO₂ Combustor Simulations

Reduced mechanisms are needed for use with computational fluid dynamic codes (CFD) utilized in the design of combustors. Typically, reduced mechanisms are created from a detailed mechanism, which contain numerous species and reactions that are computationally difficult to handle using most CFD codes. Recently, it has been shown that the detailed aramco 2.0 mechanism well predicted the available experimental data at high pressures and in highly CO₂ diluted methane mixtures. Here, a 23-species gas-phase mechanism is derived from the detailed aramco 2.0 mechanism by path-flux-analysis method (PFA) by using CHEM-RC. It is identified that the reaction CH₄ + HO₂ ⇔ CH₃ + H₂O₂ is very crucial in predicting the ignition delay times (IDTs) under current conditions. Further, it is inferred that species C₂H₃ and CH₃OH are very important in predicting IDTs of lean sCO₂ methane mixtures. Also, the 23-species mechanism presented in this work is able to perform on par with the detailed aramco 2.0 mechanism in terms of simulating IDTs, perfectly stirred-reactor (PSR) estimates under various CO₂ dilutions and equivalence ratios, and prediction of turbulence chemistry interactions. It is observed that the choice of equation of state has no significant impact on the IDTs of supercritical CH₄/O₂/CO₂ mixtures but it influences supercritical H₂/O₂/CO₂ mixtures considered in this work.