Burn time measurements of single aluminum particles in steam and CO2 mixtures

Abstract

In this study, single aluminum particles (40-80 ftm) were burned in H2O/CO2 mixtures. Burn times were measured electronically using a photo multiplier tube. In addition, the effect of oxidizer composition was determined. Burn times were also measured for single particles, quenched at various stages of combustion. Scanning electron microscope micrographs of quenched specimens were obtained. The results were used in determining particle burn times. A study of quenched particles revealed the formation of large hollow aluminum oxide spheres nearly the size of the original aluminum particle. These spheres have been reported by other investigators at both atmospheric and high-pressure conditions. It was found that burn time measurements are very sensitive to the method of analysis used. Using the results of an aluminum combustion model (Brooks, K. P., and Beckstead, M. W., Dynamics of Aluminum Combustion, Journal of Propulsion and Power, Vol. 11, No. 4, pp. 769, 770), effective oxygen concentrations were calculated for this work and other data. A relationship exists between the effective oxygen concentration and burn times reported for a given diameter. The particle burn times measured in this work compare well with other data if the effective oxygen concentration is properly accounted for.