Unsteady vaporization and ignition of a three-dimensional droplet array

Abstract

A detailed numerical simulation has been carried on a stationary three-dimensional array of heptane droplets at intermediate Reynolds numbers (Re). A goal of the simulation is to understand and quantify the interactions between droplets in the array, and to determine the change in the flow physics and chemistry caused by the droplets interactions. The flow equations solved were the low Mach number Navier-Stokes equations with variable liquid and gas, properties. In order to treat the geometry of interacting droplets the overset or Chimera grid method has been employed, and this method has accurately and efficiently simulated the droplet arrays. Simulations have been carried out at two intermediate Re and the lower Re results exhibited stronger array interactions. At higher Re there are droplet blockages, and this interaction can be quite strong. For droplets inside the array there are significant differences in droplet drag, heat transfer, and mass transfer, and the results depend on the droplet array configuration. The array geometry also has a strong influence on chemical reactions, and this is clearly seen in the ignition results. The results show clearly that groups of droplets behave differently than single droplets, and this difference is quantified with both local and global calculations of the droplet flow, heat, and mass transfer processes.