Doping rich ethylene premixed flames: Influence of C3-C5 alcohols on the structure of the one-dimensional laminar flame

The addition of alcohols to fueled mixture has been extensively documented as a practical way to significantly mitigate soot emissions by internal combustion engines. While being crucial to the initiation of some soot precursors formation, some chemical pathways attributed to the presence of alcohol-derived species remain unclear. Consequently, atmospheric steady flat laminar rich (equivalence ratio phi=1.7) ethylene/air premixed flames were established over a McKenna burner. The unburnt stream was seeded by prevaporized alcohols ranging from C-3 to C-5. Every flame was probed and sampled gases were investigated using a gas chromatography (GC) device equipped with a flame ionization detector (FID). Thus, quantitative mole fraction profiles are reported as a function of the distance to the burner tip. In total, 17 chemical compounds, including isomeric species (butene and pentene) have been detected quantitatively. Significant discrepancies among the intermediate species pool were observed, especially the amount of propene, butene, and pentene isomers (produced mostly due to the addition of propanol, butanol, and pentanol, respectively). Several kinetic mechanisms support the experimental results, none of them do reproduce properly the alkene production measured. Further numerical investigations were conducted focusing on the pathways that lead to the production of the alkenes identified. To the authors' knowledge, the results reported are the first that (i) provide experimental results for the addition of 2,2-dimethyl-propanol, (ii) document unambiguously the mole fraction profiles of the three butene and five pentene isomers, and (iii) unveil similar trends on alkene production due to the addition of C-3 to C-5 alcohols, i.e. a clear hierarchy among primary, secondary, and tertiary alcohols for the rich atmospheric premixed flames studied.

Automated summary

This study investigated the impact of adding alcohols to fuel mixtures on soot emissions in internal combustion engines. Analysis using gas chromatography revealed differences in intermediate species and alkene production due to the addition of different alcohols. The results provide new insights into the effects of alcohols on combustion processes and emissions.