Numerical simulation of the evaporation characteristics of a dimethyl ether droplet in supercritical environment

The unsteady spherically symmetrical evaporation of a dimethyl ether droplet in supercritical environment is modelled, considering real gas effects, Soret and Dufour effect, variable thermodynamic properties effects and high- pressure vapor-liquid phase equilibrium. The interface between droplet and environment disappears when it reaches the critical temperature of dimethyl ether-nitrogen system. Subsequently, the evaporation becomes a pure diffusion issue. The calculated results indicate the solubility of the ambient gas in the liquid phase is significant under supercritical conditions, and the temporal evolution of the interface temperature, reduced droplet diameter and dimethyl ether mole fraction are obtained under supercritical conditions as well. The influence of ambient pressure and temperature above critical point on the droplet evaporation characteristics was systematically investigated. Supercritical environment leads to a larger initial swelling of the droplet, when the reduced ambient pressure is 2.0 and temperature is 1.5, the maximum swelling of droplet is 7.7% larger than the initial value. Higher ambient pressure also leads a shorter fuel droplet lifetime in supercritical environment, When the reduced ambient temperature is 1.5, and the reduced pressure is varying from 1.0 to 1.5, the droplet evaporation lifetime of the dimethyl ether is reduced by 11.1%. The ambient temperature affects the droplet evaporation characteristics in a similar manner as the ambient pressure.