Ignition and combustion of boron particles

PE Nomenclature = heat capacity of the gases = boron heat capacity = oxide heat capacity = heat absorbed by reaction of B2O3 with H2O = heat absorption associated with surface reaction(s) (per unit mass of boron) = heat of vaporization of B2O3 = particle burning mass flux = heat release associated with gas-phase reaction(s) (per unit mass of oxygen) = heat release of B + B2O3 reaction = particle radius = molar rate of boron consumption = molar evaporation rate of boric oxide = molar rate of removal of B2O3 by water reaction = time = particle temperature = effective surroundings radiation temperature = particle surface temperature — ambient temperature = oxide layer thickness = ambient oxygen mass fraction = surroundings absorptivity = particle emissivity = boron density = boric oxide density = density-diffusivity product = Stef an-Boltzmann constant

Ignition and Combustion of Boron Particles and Clouds

Oxidation kinetics and combustion of boron particles with modified surface

The combustion of boron is considered from both physical and chemical points of view. The overall combustion process is separated into an ignition phase, during which the particle is covered by a layer of boron oxide, and a clean particle burning phase. During the ignition phase boron oxide production results from boron diffusion across the oxide layer, rather than the currently accepted view of oxygen diffusion. During the clean particle burning phase, boron oxidation is found to be similar to that of carbon. The chemistry of boron oxide production during this phase and the regions of kinetic and diffusion control of the burning rate are defined.

F. A. WlLLIAMS

Papers

Ignition and Combustion of Boron in O2/Inert Atmospheres