Dynamic thermal-radiation modeling of aluminum-containing RDX-beased thermobaric explosive fireballs with temperature-dependent emissivity

Thermal radiation from explosive fireballs is critical for assessing thermal damage and determining safety distances. However, existing constant-emissivity models cannot capture temperature-dependent changes in the radiative properties of combustion products. Airburst tests were conducted using 90 and 180 g charges of passivated RDX and an aluminum-containing RDX-based thermobaric explosive (TBX). A dynamic fireball thermal radiation model incorporating temperature-dependent emissivity was used to compare fireball evolution, temperature characteristics, thermal radiation responses, and influence radii. Compared with equal-mass RDX charges, the 90 and 180 g TBX charges produced fireballs with durations that were 100% and 167% longer, respectively. Their maximum-temperature peaks increased by 33.42% and 36.19%, while their average-temperature peaks increased by 54.36% and 50.80%, respectively. For TBX fireballs, the deviations between the predicted and measured peak thermal radiation intensities were below 5%. Under the engineering criteria adopted in this study, the thermal radiation influence radii of the 90 g RDX and TBX charges were 7.11 and 9.87 m, respectively. The corresponding radii of the 180 g charges were 9.46 and 12.51 m. The TBX influence radii were 38.82% and 32.24% greater than those of equal-mass RDX, respectively, and exceeded the corresponding shock wave overpressure safety radii. Overall, incorporating temperature-dependent emissivity provides a more physically realistic prediction of peak thermal radiation during the evolution of the main fireball. Moreover, the larger thermal radiation influence radii of TBX indicate that thermal radiation should be evaluated independently of shock wave overpressure when assessing thermal damage, determining safety distances, and designing thermal protection.