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Volume 80, Issue 6, June 2009
80(2009); http://dx.doi.org/10.1063/1.3133712View Description Hide Description
Detailed ignition and combustion mechanisms are needed to develop optimized propellant and energetic formulations using micron-sized metalpowders, such as aluminum.Combustion researchers have traditionally used relatively coarse metal particles to characterize the burn time dependence on particle size. However, measurements of burn times for particles below in diameter are still needed for aluminumpowders and other metal fuels. The apparatus described here sizes the particles just before the ignition event, providing a direct correlation between individual particle size and its burn time. Two lasers were utilized: a 785 nm laser diode for sizing the particles and a 125 W laser for particle ignition. The particles crossed the 785 nm laser beam just before crossing the laser beam. The particle size was determined from the amplitude of the scattered 785 nm light pulse. The burn time was determined from the duration of the visible light emission produced from the ignited particle. The in situmeasured particle size distributions compared well with the size distributions measured for the same powders by a commercial instrument using low angle laser light scattering. Our measurements with two nominally spherical aluminumpowders, suggest that the burn times increase from 0.5 to as the particle diameters increase from 3 to .