Some aspects of combustion chemistry of C1-C2 oxygenated fuels in low pressure premixed flames

The increasing utilization of renewable fuels in the transportation and industrial sectors has sparked an interest in understanding the combustion of relevant major fuel components. Among them, smaller, oxygenated compounds, are of particular importance, both as neat fuels and as potential blending agents in engines operating on practical fuels. Additionally, oxygenated exhaust species, e.g. small aldehydes, are harmful and are expected to be regulated by future emission standards. The assessment of the effect of specific fuel components on overall engine efficiency and performance, as well as on pollutants formation, needs to be tackled through a detailed kinetics approach that inherently allows such a correlation. In the present work, a single, in-house developed, detailed chemical kinetic mechanism is utilized in order to model and analyze five stoichiometric or near stoichiometric low-pressure laminar premixed flames of C1-C2 oxygenated fuels; flames of the two smallest aldehydes (formaldehyde and acetaldehyde) and the two smallest alcohols (methanol and ethanol) are considered. The mechanism is shown to satisfactorily reproduce fuel decay as well as major and intermediate species profiles. Reaction path analysis is extensively utilized in order to scrutinize the controlling elementary steps. Parts of the mechanism are identified for further model improvement, based on critical evaluation of available specific rate constants. Early branching ratios and reactions between the major carbonyl or alkoxy products with oxygen carriers, and in particular reactions with O2, appear to be pivotal for the overall oxidation process.