A molecular dynamic study of evaporation/supercritical-transition inter-relationship and multicomponents interaction for alkane/alcohol droplets

Abstract

The behavior of droplets going through trans-critical conditions from subcritical to supercritical exhibits different features. The influence of multicomponent droplets on the relationship between supercritical transition and evaporation has not been determined. In the present work, molecular dynamic simulations for both single-component and two-component hydrocarbon droplets comprising alkanes (heptane, dodecane, and hexadecane, which are abbreviated to C7, C12, and C16, respectively, in present paper) and alcohol (n-butanol, which is abbreviated to BuOH), whose diameters are 30 nm, are conducted under various trans-critical conditions. To ensure efficiency and accuracy, the simulations are conducted under nitrogen atmosphere. The supercritical transition rate of droplets is quantified by the temporal declining of the maximum fuel mole fraction, and the evaporation rate is measured by the reduction of their radius. The inter-relationship between the supercritical transition and evaporation is mainly influenced by the ambient pressure, where the supercritical transition of droplets becomes more dominant under conditions with higher pressure. Furthermore, the separate phase-change processes and spatial stratification phenomena are discovered for trans-critical n-butanol/hexadecane droplets. Ultimately, by comparing the supercritical transition regions of the binary droplets and the corresponding unary droplets, the influence of intercomponent interaction on the phase-change process of binary droplets is discussed.