Development of an n-heptane-n-butanol-PAH mechanism and its application for combustion and soot prediction

Abstract

A reduced chemical reaction mechanism was developed for modeling the combustion process and soot emissions for both non-oxygenated and oxygenated hydrocarbon fuels. A detailed poly-aromatic hydrocarbon (PAH) mechanism was reduced and embedded into a reduced n-heptane mechanism for describing the formation of PAH up to four rings (A4) and for soot prediction. A reduced n-butanol mechanism was combined with the n-heptane-PAH mechanism to investigate of effects of oxygenated n-butanol fuels on combustion and soot emissions. The final mechanism consists of 76 species and 349 reactions. The mechanism was validated with experiments in shock tubes, constant volume chambers and test-bed engine data. New experiments were also conducted and reported in current investigation and have been used to validate the proposed mechanism. The effects of oxygenated additives on combustion and soot emissions under diesel-like conditions were also investigated. The results show that the present simulations give reliable predictions of combustion and soot emissions. The results also agree with the general soot formation processes near the lift-off length in mixing controlled diesel fuel jets, and the present mechanism can be used to predict the combustion and soot emissions of diesel, n-heptane and n-butanol fuels in 3D CFD simulations.