Reduced mechanisms for methanol oxidation under hydrothermal flames using a directed relation graph with sensitivity analysis and error propagation

A revised detailed mechanism (RDM) including 173 species and 1011 reactions for methanol oxidation under hydrothermal flames is developed via modifying a methanol gas-phase combustion mechanism with pressure and thermodynamic corrections and validated with experimental data. Different skeletal mechanisms are generated via the directed relation graph (DRG), the DRG with error propagation (DRGEP), the DRG with sensitivity analysis (DRGSA), and the DRGEP with sensitivity analysis methods. Although the skeletal mechanisms have different reaction paths, the evolutions of the main species in the RDM are generally reproduced. The most compact mechanism of 12 species and 35 reactions is obtained via the DRGSA method with an error of 7.59%. The temperatures of hydrothermal flames predicted from the skeletal mechanisms with different reduction methods agree well with those from the RDM within most operating ranges except the 12-species mechanism under hypoxic conditions. The increase in the reduction degree increases the error of the ignition delay time, while the reduced mechanisms have better adaptability in predicting the ignition delay time at higher preheating temperatures. The increases of preheating temperature and methanol concentration decrease the error in the prediction of the laminar flame speed with the reduced mechanisms. Moreover, the mechanisms with different reduction degrees have little effect on the extinction temperature, with an error of 4-8 degrees C.