Molecular Dynamics Study on Combustion Characteristics and Soot Formation Reactions of C4 Isomers Blended with NH3

To achieve clean combustion of C4 hydrocarbon fuels, five typical C4 structural isomers were selected and reactive molecular-dynamics simulations with the ReaxFF force field were performed to compare combustion characteristics under neat-fuel and NH3-blended conditions. The results reveal strong structural dependence in C4 isomer combustion: terminal double bonds and tertiary C-H bonds govern ignition reactivity in the early stage. Carbon-skeleton cleavage controls overall reaction efficiency in the intermediate stage. Olefinic intermediates tend to persist in the late combustion phase, with distinct soot-precursor distributions across fuels. Ammonia addition markedly shortens oxygen-consumption duration for all systems, suppresses CO2 formation, and increases H2 and H2O yields. For soot formation, neat olefins produce far more six-membered rings than alkanes. NH3 blending raises the system-level C/H atomic ratio, and nitrogen atoms are incorporated into soot skeletons via nitrogen-containing functional groups.