Pyrolysis and oxidation mechanisms of ethylene and ethanol blended fuel based on ReaxFF molecular dynamics simulation

Abstract

To gain detailed atomic-level insights into the reaction mechanisms associated with the oxy-fuel combustion of ethylene and ethanol, ReaxFF reactive force field molecular dynamics simulations were performed to analyze the behavior of their high-temperature pyrolysis and oxidation. Results showed that the main reaction of pure ethylene involves the formation of long carbon chains by C–C polymerization in an oxygen-free environment. The polycondensation-cyclization of long carbon chains significantly contributes to the formation of polycyclic aromatic hydrocarbons (PAHs). The addition of ethanol enriches the initial reaction pathways of ethylene. For instance, ethanol participates in the following reactions: C2H4 + C2H6O → C4H10O, C2H6O + C2H4 → C2H5 + C2H5O, and C2H6O + C2H4 → C2H5 + H2O + C2H3. Ethanol inhibits the growth of long carbon chains, with a more pronounced effect at higher ethanol concentrations. In an oxygen atmosphere, the decay rate of ethylene decreases significantly, and its main reaction pathway involves dehydrogenation and oxidation with the assistance of OH, HO2, H, and O2. The final products are released in the form of CO, CO2, and H2O. In addition, the formation of soot particles is mainly divided into three steps: (i) ethylene aggregates to form long carbon chains, (ii) rearrangement and cyclization of long carbon chains, and (iii) growth of PAHs.