Oxidizer and Pressure Effects on the Combustion of 10-micron Aluminum Particles

An experimental investigation of the combustion times of nominally 10-μm spherical aluminum particles burning in a shock tube is presented. Burn times were measured by observing the light emission from AlO, a combustion intermediate, at elevated ambient temperatures (∼2650 K) while independently varying both oxidizer composition (O 2 , CO 2 , and H 2 O in Ar) and pressure (3-30 atm). Burn times decreased with increasing oxidizer mole fraction for all oxidizers. The oxidizer species had a strong effect on the burn time, with oxygen giving the shortest burn times, followed by carbon dioxide and then water vapor. Burn times in CO 2 and H 2 O were found to increase weakly with increasing pressure, while burn times in oxygen decreased as pressure increased. At the small particle sizes investigated here, there is some evidence that surface processes could be playing an important role in the overall rate of aluminum combustion.