Development of a combined reduced primary reference fuel-alcohols (methanol/ethanol/propanols/butanols/n-pentanol) mechanism for engine applications

A combined reduced primary reference fuel (PRF)-alcohols (methanol/ethanol/propanols/butanols/n-pentanol) combustion kinetic mechanism composed of 161 species and 622 reactions was developed for engine combustion simulations. The obtained reduced PRF-alcohols mechanism was constructed with a hierarchical structure. Minor adjustments were performed to ensure the predictive performance against experimental results. The reduced PRF-alcohols mechanism adequately predicted experimental ignition delays, laminar flame speeds, and species mole fraction profiles. New homogeneous charge compression ignition experiments fueled with 75% (mol.) n-propanol/25% n-heptane, 75% i-propanol/25% n-heptane, and 75% n-pentanol/25% n-heptane blends were also collected and served as further mechanism validations. By coupled with the toluene-polycyclic aromatic hydrocarbons sub-mechanism, the reduced PRF-alcohols mechanism was used for the three dimensional modeling studies to investigate the direct injection compression ignition (DICI) combustion fueled with diesel/alcohol blends at the 5% fuel oxygen content. Zero-dimensional modeling studies were also conducted. The modeling results indicated that in DICI combustion, it was the different physical mixing qualities incurred by the different fuel reactivity dominated the soot formation but not the different carbon chain chemical structures. The O atom of the fuel molecule was more efficient than the O2 molecule for the soot oxidation.