Development of a reduced tri-propylene glycol monomethyl ether–n-hexadecane–poly-aromatic hydrocarbon mechanism and its application for soot prediction

Abstract

A reduced chemical kinetic mechanism for tri-propylene glycol monomethyl ether has been developed and applied to computational fluid dynamics calculations for predicting combustion and soot formation processes. The reduced tri-propylene glycol monomethyl ether mechanism was combined with a reduced n-hexadecane mechanism and a poly-aromatic hydrocarbon mechanism to investigate the effect of fuel oxygenation on combustion and soot emissions. The final version of the tri-propylene glycol monomethyl ether–n-hexadecane–poly-aromatic hydrocarbon mechanism consists of 144 species and 730 reactions and was validated with experiments in shock tubes as well as in a constant-volume spray combustion vessel from the Engine Combustion Network. The effects of ambient temperature, varying oxygen content in the tested fuels on ignition delay, spray lift-off length and soot formation under diesel-like conditions were analyzed and addressed using multidimensional reacting flow simulations and the reduced mechanism. The results show that the present reduced mechanism gives reliable predictions of the combustion characteristics and soot formation processes. In the constant-volume spray combustion vessel simulations, two important trends were identified. First, increasing the initial temperature in the constant-volume spray combustion vessel shortens the ignition delay and lift-off length and reduces the fuel–air mixing, thereby increasing the soot levels. Second, fuel oxygenation introduces more oxygen into the central region of a fuel jet and reduces residence times of fuel-rich area in active soot-forming regions, thereby reducing soot levels.