Comparison Study on Burning and Ignition Characteristics for Single Aluminum and Magnesium Particles

Ignition and burning characteristics of single aluminum and magnesium particles are experimentally investigated. Burning time, ignition delay, flame temperature, and ignition temperature were measured. The single metal particle (30-110 μm in diameter) is uplifted by an electrodynamic levitator, exposed and ignited by a CO2 laser. The thermal radiation intensity was measured using the photomultiplier tube and combustion history was monitored by high-speed cinematography. Two-wavelength pyrometry measured the temperature of the burning particles. The burning time of the Al particle is approximately 5 to 8 times longer than that of the Mg particle. Exponents of Dn-law, for the burning rate of the magnesium and aluminum particles of diameters less than 110 μm, were found to be 0.6 and 1.5, respectively. The instant of the aluminum ignition was clearly distinguished with the ignition delay time little less than 10 ms, however the burning history of the magnesium particle exhibited no clear instant of the ignition. The ignition delay time of the magnesium particle (less than 110 μm) might be in the range from 50 to 200 ns. The flame and ignition temperatures of a single Al particle are slightly lower than the boiling and melting point of Al2O3