Peering through the flames: Imaging techniques of reacting aluminum powders
Combusting metals burn at high temperatures and thus emit high levels of radiation in the visible spectrum which can over-saturate high-speed image recording devices. But filtering out the luminescence can result in limited information required for thorough combustion characterization. A method for “seeing through the flames” of a highly luminescent aluminum particle reaction is presented using copper vapor laser illumination synced to a high-speed camera. A statistical comparison of combusting aluminum particles between filtered halogen and laser illumination shows the effectiveness of this diagnostic approach. When ignited by an electrically induced plasma, aluminum particles are entrained as solid agglomerates that rotate about their centers of mass and are surrounded by emitted, burning gases. The average agglomerate diameter is 160 micrometers but only 50 micrometers when imaged with copper vapor laser illumination. These results show evidence that alternative imaging techniques are required to resolve the complexities of metal particle combustion.