Modeling droplet breakup processes under micro-explosion conditions

This paper presents a numerical model of micro-explosion for multicomponent droplets. The first part of the model addresses the mass and temperature distribution inside the droplet and the bubble growth within the droplet. The bubble generation is described by a homogeneous nucleation theory, and the subsequent bubble growth leads to the final explosion (i.e., breakup). The second part of the model determines when and how the breakup process proceeds. Unlike ad hoc/empirical approaches reported in the literature, the size and velocity of sibling droplets were determined by a linear instability analysis. After validated against available experimental data for bubble growth and homogeneous nucleation, the developed model was first used to study the effects of various parameters on the onset of micro-explosion. It was found that, optimum composition and high ambient pressure favor micro-explosion; however, extremely high pressures suppress micro-explosion because the volatility differential decreases. The vaporization behavior of an oxygenate diesel blend was analyzed at the end. It was found that micro-explosion is possible under typical diesel engine environments for this type of fuel. Occurrence of micro-explosion shortens the droplet lifetime, and this effect is stronger for droplets with larger sizes or a near 50/50 composition.