Ignition and Combustion of Boron Particles Over a Wide Temperature Range in a Shock Tube

Boron, which possesses high mass calorific value and volume calorific value, is a potential high-energy-density fuel for solid-fueled scramjets. Investigating the ignition and combustion characteristics of boron particles is important for its application. In this study, ignition and combustion experiments have been conducted on amorphous boron particles with an average size of ∼3 μm and crystalline boron particles with an average size of ∼26 μm using a shock tube in a 79%Ar/21%O2 atmosphere under a wide temperature range of approximately 2000–4000 K and pressures of approximately 1 and 5 atm. The effects of temperature and pressure on the ignition and combustion times have been investigated. The results reveal that both the ignition and combustion times of boron particles decrease with increasing temperature or pressure. Quantitative relationships have been yielded by the regression fitting of the experimental data. For amorphous boron particles, the ignition delay and combustion times are τ=361×P−0.33±0.03×exp4978±357T and τ=829×P−0.17±0.05×exp4509±450T, respectively. For crystalline boron particles, the ignition delay and combustion times follow τ=682×P−0.24±0.04×exp4540±524T and τ=640×P−0.23±0.04×exp5657±437T, respectively. Additionally, a simplified model for the ignition and combustion of boron particles has been proposed and compared with the experimental results. The computational results reproduce the expected trends, showing both ignition and combustion times decrease with increasing temperature or pressure.