Reactive molecular dynamics combustion simulation of sustainable aviation fuel alternative components

Sustainable Aviation Fuel (SAF), constituting an important technological pathway for the aviation industry to achieve carbon neutrality goals, has attracted significant attention due to its potential to substantially reduce carbon emissions. However, the complex multi-component nature of SAF has resulted in unelucidated competitive/synergistic reaction mechanisms between components and unclear pollutant generation pathways during its combustion process. Existing ReaxFF-MD studies on SAF mainly focus on single-component surrogates, lacking systematic exploration of multi-component interaction mechanisms under actual aero-engine high-temperature conditions. In this paper, based on the reactive molecular dynamics (ReaxFF-MD) simulation method, a kinetic model of the high-temperature combustion process was constructed for the alternative components of a typical SAF multi-component mixture system, and pyrolysis and oxidation reaction paths alongside free radical generation were systematically investigated. Through comprehensive comparison of potential energy (PE) changes, combustion rates, intermediate product distributions, and final products at different temperatures and oxygen contents, the microscopic mechanism of SAF multi-component synergistic combustion was uncovered, while the regulatory effects of temperature on bond cleavage pathways and radical evolution, as well as the influence of excess air coefficient ( λ ) on combustion efficiency and product distribution, were revealed. Simultaneously, the reaction mechanism of SAF was obtained by analyzing the reaction paths. The results show that, compared with the low-temperature conditions, under high-temperature conditions, SAF has a faster combustion rate, a greater total number of species, and higher generation and consumption rates of free radicals. Furthermore, oxygen content exerts a significant effect on combustion efficiency and product distribution. Increasing the excess air coefficient enhances the reaction rate to a certain extent but offers no substantial benefit when the excess air coefficient exceeds 1.5. Notably, most PE attains its maximum during the cleavage of C–C and C–H bonds, indicating that bond scission is the rate-determining step in the initial stage of SAF combustion. This study provides fundamental theoretical support at the microscopic level combined with reaction path analysis for optimizing the combustion performance of SAF alternative components and developing clean combustion technology, thereby accelerating the decarbonization process of aviation fuels.