Oxidation mechanisms of ammonia and ethanol mixed fuel by using the ReaxFF-MD simulation

ReaxFF molecular dynamics simulations were employed to investigate the behavior of ammonia and ethanol mixed fuel in different conditions, focusing on their combustion reaction mechanisms, intermediates, free radicals, and final product formation at different equivalence ratios. The results reveal that ammonia is primarily consumed by OH free radicals, leading to the formation of the NH2 free radical. NH2 radical undergoes further transformations, forming H2NO, H3NO, HNO, HO2, NO, NO2, HONO, and NH free radicals. The CH3, an intermediate of ethanol, influences the abundance of other free radicals such as H and OH, which also leads to a significant increase in CH2O. In oxygen-rich conditions, OH, HO2, and H2O2 demonstrate higher concentrations compared to oxygen-poor conditions. The NOx species include NO, NO2, and NO3 in rich- and stoichiometricoxygen conditions, whereas in oxygen-poor conditions, only NO is formed. The number of H2O decreases as the proportion of ethanol decreases due to the lack of O atoms, and the amount of H2 continues to increase in the oxygen-poor system. The limited availability of oxygen alters the reaction mechanism, reducing the occurrence of primary form reactions of H2O with the assistance of O, OH, and HO2. Instead, an increasing number of branching chain reactions become prominent at high temperature, leading to the formation of a significant amount of H2.