Evaporation and dynamic characteristics of a high-speed droplet under transcritical conditions

Abstract

An evaporation and aerodynamic interaction model is developed for an isolated droplet introduced into transcritical and strong convective environments. The new numerical model takes into account variable thermophysical properties, gas solubility in the liquid phase, and vapor-liquid interfacial thermodynamics. The proposed model is verified by high-speed photography experiments carried out under different operating conditions. The influences of ambient conditions on the transcritical evaporation and aerodynamic interaction are investigated with the new model. The results indicate that (1) with increasing the liquid-gas relative velocity, the spatial temperature distribution becomes more nonuniform initially and then more uniform; (2) the drop drag increases rapidly with ambient pressure in the initial period and then significantly decreases; and (3) when the ambient temperature is lower than 1.5 times the fuel critical temperature, the droplet drag force decreased with the ambient temperature; otherwise, the drag force increased initially and then decreased with the ambient temperature.