Reduced Kinetic Mechanism for Methanol Combustion in Spark-Ignition Engines

A reduced kinetic mechanism for methanol combustion at spark-ignition (SI) engine conditions is presented. The mechanism consists of 18 species and 55 irreversible reactions, small enough to be suitable for large eddy simulations (LES). The mechanism was reduced and optimized using the comprehensive mechanism (AramcoMech 2.0) as a starting point, to maintain performance at stoichiometric conditions for the pressure (10-50 bar) and temperature ranges relevant for SI-engine conditions. The mechanism was validated against experimental data for ignition delay at 1050-1650 K, flow reactor at 783 K and jet-stirred reactors at 800-1150 K, and simulated validation targets for laminar burning velocity under conditions where no experimental data are available. The mechanism performs well for pollutant formation (CO and CH2O), ignition delay, and laminar burning velocity, which are all important properties for LES of engines. Two other reduced mechanisms for methanol combustion, containing around the same number of species and reactions, were tested for comparison. The superior performance of the mechanism developed in the present work is likely a result of that it is specifically produced for the relevant conditions, while the other mechanisms were developed for a limited set of conditions compared to the present work. This highlights the importance of careful selection of reduced mechanisms for implementation in computational fluid dynamics simulations.