(612e) Combustion Characteristics of Boron and Boron Based Composites in Different Flow Configurations

Song Wang, Mirko Schoenitz, Edward L. Dreizin

New Jersey Institute of Technology

Newark, NJ 07103

Abstract

Due to its high heat of combustion, boron is widely considered as an attractive fuel. Recently, ternary B·Mg·I₂ and B·Al·I₂ composite powders were prepared as reactive materials generating biocidal combustion products. The materials contained 20 wt % of I₂ were shown to be effective in inactivating aerosolized microorganisms. The aim of this paper is to characterize the effect of flow conditions on combustion dynamics of particles of boron and composite B·Mg·I₂ and B·Al·I₂ materials. For all materials, powder particles were carried by a laminar air flow to cross a focused beam of a CO₂ laser. A cylindrical air knife was used to generate a turbulent flow pattern above the laser beam. In different experiments, particles ignited by the laser continued burning in either laminar or turbulent flows. Particle streaks were photographed at different flow conditions. For boron particle, staged combustion was observed, consistently with previous work. Streaks were brighter for the aluminum-containing composite as compared to that containing magnesium. Oscillatory emission patterns were observed at the end of combustion for boron and aluminum containing composite, but not for the magnesium containing composite. Particle burn times and combustion temperatures were obtained for all experimental configurations. For boron, the particle burn times in the laminar flow were nearly twice as long as those in the turbulent flow. Boron combustion temperature was close to 3100 K in the laminar flow and decreased to 1500 K at the highest turbulence intensity. However, the combustion characteristics of composite materials were not altered by the flow conditions. The burn times, which were slightly lower than for boron in a laminar flow and combustion temperatures (close to 2000 and 2500 K for B·Al·I₂ and B·Mg·I₂, respectively) remained nearly the same for all flow configurations.