First ever atomistic-scale simulation of hydrocarbon ignition front propagation under supercritical conditions: Validation against experiment and continuum model

The combustion characteristics of hydrocarbon fuel/oxidizer mixtures have been studied extensively for the past decades due to their importance in practical combustion problems. One of these characteristics is the laminar flame speed and allied to this is the ignition front propagation speed. An atomistic-level insight is required to understand in detail the underlying physics and chemistry. Such insight is difficult to obtain through currently available experimental and numerical techniques. Here, for the very first time, we propose a method of calculating the ignition front propagation speed from atomistic-scale simulation using ReaxFF molecular dynamics simulations. Results reported in this study are for the combustion of hydrocarbons under supercritical conditions (P=55MPa and T_u=1800K), as elevated pressure and temperature accelerate the dynamics for reactive Molecular Dynamics (MD) simulations and allows obtaining results within feasible computational time. Our proposed method has been implemented for different types of hydrocarbons; alkyne, alkane and aromatic; and is shown to be able to successfully capture the correct trend of reactivity of these hydrocarbons. The MD simulations have been further corroborated with results acquired from continuum simulations performed. These results have been found to compare reasonably well with the ReaxFF results, which demonstrate that ReaxFF can be used as a promising tool to study flame speed/ignition front speed of supercritical hydrocarbon combustion.