Initial Mechanism and Kinetics of Diesel Incomplete Combustion: ReaxFF Molecular Dynamics Based on a Multicomponent Fuel Model

This work attempts to investigate the incomplete combustion of a multicomponent fuel model using ReaxFF-MD simulations. The main products of incomplete combustion simulation included H-2, CO, H2O, and CO2. Temperatures produced different effects on different products. At lower temperatures, a larger increasing rate of the number of products was found at a later stage, whereas the increasing rate of the number of products would be diminished over time at higher temperatures. The pressure-dependent simulations indicated that the high pressure could promote the combustion process, especially the production of H-2. The analysis of mechanisms and pathways of the combustion process indicated that the CC bond dissociation dominated the early stage of the combustion mechanism of paraffin, whereas isomerization, H-abstraction, and CC bond formation were observed in other systems. Ethylene (C2H4) was the product of beta-scission of paraffin and naphthene, whereas ethyne (C2H2) was the product of beta-scission of aromatic structures. A huge fluctuation range was observed in the variation trends of OH and CH2, which revealed the high reactivity of these two radicals. Besides, collision was the main reason for the initial formation of coke instead of thermal deposition in the gas phase under extremely high temperatures. This work further suggests that ReaxFF-MD is a promising approach for investigating the combustion behavior of hydrocarbon models at high temperatures.