Dispersion of Boron Particles from a Burning Gel Droplet

摘要

This study addresses the use of a shrinking core model in order to evaluate the combustion behavior of boron pyrotechnic clusters suspended in a kerosene-based gel fuel. Boron particles are combined in a low-oxidizer pyrotechnic mixture forming clusters that are dispersed in the gel droplet. During the combustion of the gel droplet, the organic phase evaporates from the droplet surface, forming a porous layer of dry particles. The pyrotechnic clusters are designed to ignite after the formation of the dry layer, when boron particles are not bonded by any liquid phase and can be easily dispersed. It is established that the time needed to reach initial boron scattering depends on the droplet diameter and absorbed heat flux. No dependence of the time delay for initial boron scattering on the boiling temperature is observed. Three pyrotechnic mixtures are used in order to investigate the influence of the pyrotechnic activation temperature on the formation of the dry layer. Boron pyrotechnic dispersion based on ammonium perchlorate (NH4ClO4) is limited to a low gel boiling temperature; whereas pyrotechnic dispersion based on NaClO4 or potassium perchlorate, which each have a higher activation temperature, can ensure the formation of a dry layer that allows scattering of the boron particles.