Characteristics of Aluminum Combustion Obtained from Constant-Volume Explosion Experiments

Abstract

Combustion of aluminum powders was studied using a constant volume explosion (CVE) experiment with varied powder mass loads, particle sizes, and environment compositions. A simplified model of aerosol combustion in CVE experiment was used to extract the information about the burning velocity from the measured pressure traces; additional assumptions were used to evaluate the flame thickness. It was observed that an increase in oxygen concentration always results in higher rates of pressure rise, shorter induction periods, and shorter aerosol combustion times. Similarly, adding methane to the gas mixture always results in shorter induction times, greater rates of pressure rise, and higher maximum combustion pressures. It was further observed that at increased oxygen concentrations, the kinetics of Al combustion may be faster than that of gas-phase combustion of methane. In most experiments, there was a period when the flame propagation occurred in a quasi-steady mode, with nearly constant burning velocity and flame thickness. The burning velocities measured for Al aerosols vary approximately from 0.25 to 1.3 m/s and compare well with those reported earlier for similar size Al powders. The aluminum aerosol flame thickness was evaluated to vary approximately from about 2.5 to 12 mm. Experimental results suggest that radiation is the dominant mechanism of heat transfer for the aerosol flames.

Keywords:

• Aerosol flame thickness
• Aluminum combustion
• Burning velocity
• Dust flames

ACKNOWLEDGEMENTS

This work was supported by Defense Threat Reduction Agency (DTRA). Interest, encouragement, and support of Drs. S. Peiris and W. Wilson of DTRA are gratefully acknowledged.