Molecular Dynamics Simulation of Fuel Drop Vaporization Under Sub- and Supercritical Ambient Conditions

Based on the method of molecular dynamics simulation, the evaporation process of a single alkane droplet in nitrogen environment was simulated. The remarkable difference of droplet evaporation characteristics under subcritical and supercritical conditions was revealed. The molecular dynamics simulation result of the evaporation process of n-dodecane droplets in nitrogen environment shows that the temperature of the droplets keeps rising under the conditions of supercritical temperature and pressure, which can exceed the critical temperature of fuel components. At this time, the density difference between the droplets and the surrounding gas phase region almost disappears, and the gas-liquid interface becomes difficult to distinguish, which is obviously different from the typical gas-liquid two-phase evaporation characteristics under subcritical conditions. The evaporation rate increases with the increase of ambient temperature. In a lower pressure range, increasing the ambient pressure can increase the evaporation rate of droplets. However, when the pressure reaches a certain value, the evaporation rate will decrease with the increase of ambient pressure, and the minimum pressure required for droplets to be converted into supercritical evaporation will decrease with the increase of ambient temperature. For two-component mixed droplets, under subcritical environment, the light components in the droplets evaporate preferentially, while under supercritical environment, the components in the droplets almost keep simultaneous evaporation, and the two fuel components jointly dominate the complete evaporation process of the droplets. © 2023, Editorial Office of the Transaction of CSICE. All right reserved.