Development and application of a practical diesel-n-butanol-PAH mechanism in engine combustion and emissions prediction

A practical generation mechanism of n-butanol-polycyclic-aromatic-hydrocarbons (PAH) in diesel engine was established, and the generation kinetics of NOx and soot was embedded into the engine simulation. n-Dodecane, iso-cetane, iso-octane, toluene and decalin were used as a surrogate of diesel so as to achieve the purpose of physical and chemical properties of surrogate closer to the actual fuel. In order to further describe the soot behavior, the PAH model includes the formation pathways of A(1)-A(7). The mechanism including 149 species and 497 reactions was first validated by zero-dimensional ignition delay, and the combustion properties of each constituent and diesel/n-butanol mixture were precisely captured by the mechanism. The combustion and emission characteristics of diesel/n-butanol blends were then studied using a computational fluid dynamics model coupled with the current mechanism in the engine operated under various exhaust gas recirculation and split injection strategies. Moreover, the findings also pinpoint that relative to 100% diesel, B30 exhibits decreasing emissions of NOx and soot at 25% EGR rate with the pilot/main injection timing of 342.5 degrees CA/360.5 degrees CA and the pilot injection ratio of 8% or 10%.