Manipulating Grouping Dynamics of Nanoscale Boron Particles as Basis for Environmentally Friendlier Combustion and Efficient Filtration

Elemental boron has one of the highest volumetric heat of combustion known and therefore submicrometer and nanosized boron powders are high energy density fuels. At the same time, boron is to some extent an environment-friendly fuel because the main barn-product, boron oxide B 2 O 3, is produced in the solid state. A review of the characteristics of boron particles and powders is given. It sets the basis for the focus of this study that is on the tendency of submicrometer and nanosized boron particles to group/cluster in an oscillating flow. Such a tendency may lead to coagulation of boron particles depending on their size, shape, and stickiness, as well as on the flow characteristics. This situation occurs when boron particles are injected into a combustion chamber and are subjected to flow oscillations. Analysis of the grouping behavior is a prerequisite for describing how such particle-oscillation interactions may affect the combustion process, flame characteristics, and pollutants' emission. Besides grouping due to flow oscillations, the dynamics of submicrometer particles is governed by Brownian motion, and this combined effect is discussed here. The analysis points out how controlling flow oscillations can lead to a more environment-friendly combustion process.