A molecular dynamics investigation on fuel vaporization and mixing characteristics under sub/supercritical conditions

Molecular dynamics simulation is performed to study the influence of environmental pressure on the mixing process. Based on the OPLS-AA full-atomic potential function, the gas-liquid-gas simulation box model is used to study the evaporation characteristics of n-heptane at different environmental conditions. The results show that compared with the subcritical environment, the nitrogen molecules in the supercritical condition can diffuse into the liquid phase region earlier, and the temperature of the liquid phase rise faster, and then a unified supercritical fluid could be formed. Based on the density profile, a gas-liquid-gas interface thickness is defined and the interface thickness is widened as the ambient pressure increase, resulting in the conventional subcritical evaporation transition turbulent mixing process.