Numerical research on a vaporizing fuel droplet in a forced convective environment

Abstract

A comprehensive numerical model is developed to study a vaporizing n-heptane droplet in a forced convective environment under different temperature conditions, which includes high-pressure effects, liquid phase internal circulation, variable thermophysical properties, solubility of inert species into the liquid phase, and gas and liquid phase transients. Numerical predications of time histories of the dimensionless diameter square of a vaporizing fuel droplet within a zero gravity environment are in very good agreement with the micro-gravity experimental data. The numerical results show that at higher ambient pressure (such as 4 MPa) the droplet swells initially due to the heat-up of the cold droplet and its subsequent regression rate is far from following the d 2-law during the early stages of droplet evaporation. However, at the ambient pressure of 0.1 MPa, the droplet swells are not obvious. The droplet presents an almost d 2-law behavior in later stages of droplet evaporation for all considered pressures (up to 4 MPa). The numerical results also show that the droplet lifetime decreases with increasing ambient temperature. For example, the droplet lifetime at the ambient temperature 1200 K can be only 50–60% of the droplet lifetime at the ambient temperature 600 K. The final penetration distance of the vaporizing droplet decreases almost linearly with the ambient temperatures considered.