Lean Dust Combustion for Varied Surface Energy Aluminum Particles: Analyzing Dispersion and Light Emission

The lean combustion of micron-sized aluminum (Al) dust post ballistic impact was studied bi-spectrally in the visible (VIS) and near-infrared (NIR) using high-speed imaging. Powders were delivered loosely via a novel sabot design. Two identically sized Al powders were studied, one was untreated (UN), the other processed using a thermal treatment and called super-quenched (SQ). The SQ Al powder is known to have reduced surface energy compared to UN Al powder, which is induced by the annealing-quenching treatment. A field emission fraction is introduced as a metric that characterizes the light emission dispersion of burning powder and relates to combustibility. In the case of SQ Al, visible light emission from dispersed powder decays slower compared to UN Al. The peculiarities in powder dispersion were attributed to different combustion regimes and further confirmed by X-ray diffraction (XRD) analysis of post-burn products, which demonstrated different residue phase compositions.