Mathematical modeling of puffing and microexplosion in emulsified fuel droplets containing several bubbles : a case study on n-dodecane/water droplet

Abstract

This paper presents a theoretical model for microexplosion and puffing in a single isolated emulsion droplet at high ambient temperature and one atmospheric pressure. The model considered transient heating of the droplet, bubble growth dynamics, bubble motion, and bubble interactions (e.g., bubble coalescence). The bubble growth is determined by solving a modified Rayleigh equation which considered bubble interactions. The model considered multiple bubbles inside a fuel droplet which were not accounted for in the models proposed in previous studies. The model is applied to simulating the microexplosion of n-dodecane/water droplets. The simulated microexplosion delay times are compared with the experimental data from the literature, with good qualitative and quantitative agreements obtained. Results show that microexplosion delay time diminished by 40% and 50% for a 10-times increase in the initial bubble diameter and changing the bubble location from droplet center to 0.4 times the droplet radius, respectively. For multiple bubbles inside the droplet, the microexplosion delay time converges to a minimum threshold value without further changing the bubble number. The simplified model bears practical potential in enabling spray combustion modeling of water-emulsified fuels with considerably reduced computational costs.