Oxidation mechanism of methane fuel blended with dimethyl ether/ hydrogen/ammonia via ReaxFF molecular dynamics simulation

Hydrocarbon fuels used in micropower systems offer significant advantages, such as high energy density, lightweight properties, and extended power supply duration, making them the focus of widespread interest. Methane is particularly favored due to its excellent combustibility, ease of preparation, and convenient storage. In this study, ReaxFF molecular dynamics simulation is employed to investigate the influence of three additives (dimethyl ether, hydrogen, and ammonia) on the combustion mechanism of methane fuel. Results show that the pathways of CH4 mainly involve dehydrogenation and oxidation reactions. In CH4/C2H6O system, dimethyl ether is predominantly consumed via two pathways: C-O cleavage and dehydrogenation. These pathways form a significant quantity of active free radicals (such as CH3 and CH3O). In the case of CH4/H2 combustion, hydrogen is consumed to provide H, OH, and HO2 active free radicals via reactions such as H2 + OH -* H2O + H, H2 + O2 -* 2OH, and H2 + 2O2 -* 2HO2. In the combustion of CH4/NH3, ammonia initially undergoes a dehydrogenation reaction involving OH, O, and H free radicals, resulting in the formation of NH2. Subsequently, 65.57 % of NH2 undergoes further reactions to form H2O2N, while 16.39 % of NH2 forms NH radicals. The presence of additives influences the final products in different systems. In the CH4/C2H6O system, the final products include CO, CO2, H2, and H2O. In the CH4/H2 system, the final products consist of CO, CO2, and H2O. Lastly, in the CH4/NH3 system, the final products comprise CO, CO2, H2, NO, NO2, and H2O.