Characterization of aluminum powder ignition

Heating rate effect and particle size effect on ignition temperature of Al powder were studied to collect data for development of a possible Al powder ignition model. Aluminum ignition is associated with a highly accelerated burn rate and high combustion enthalpy. A new ignition model, which can adequately interpret these conditions, is needed to develop better propulsion fuels, explosives and incendiaries that use Al as an additive. This experimental program was focused on preparing framework for characterization of ignition kinetics of Al powder by determining the ignition temperature for different, systematically varied, heating rates and particle size. The experimental setup involved igniting Al powder coated on a small length of an electrically heated carbon filament. A three-color pyrometer and a high-speed camera were used in the project to determine the filament surface temperature at the instant of ignition. When using the pyrometer, a sharp rise in a photodiode signal from the powder coating was used to determine the ignition moment. The high-speed camera recorded both the temperature and the ignition moment. Two Al powders with different particle size (Alfa Aesar, Al 10 - 14 μm and Al 3 - 4.5 μm) were investigated. The powders were ignited at three different heating rates. A higher ignition temperature was observed for higher heating rate for both the powders. The powder with larger particles ignited at higher temperature for same heating rate