Analysis of heat-release during TNT/Aluminum afterburning by means of numerical simulations

Abstract

The present study investigates the afterburning from an explosion of a spherical 2,4,6-Tri-Nitro-Toluene (TNT) charge containing aluminum particles at four different Heights of Burst (HoB), to demonstrate that numerical simulations can facilitate the evaluation of the performance of Enhanced Blast eXplosives (EBX). The simulations are conducted using a two-phase Large Eddy Simulation model in Euler-Lagrange form, incorporating interaction between gaseous and solid phases by means of a two-way coupling. Finite rate Arrhenius chemistry is used to simulate the afterburning process, thereby enabling the examination of the separate heat-release contributions from carbon and aluminum afterburning reactions. The simulation results indicate the heat-release contribution from the aluminum reactions is significantly higher than from the carbon reactions, also does the heat-release from aluminum reactions, for all HoBs, fluctuate more in time compared to the heat-release from the carbon reaction. Most of the heat-release from carbon seems to occur at early times, after which the afterburning of carbon stagnates at a steady rate. The heat-release from aluminum reactions is more intermittent and is thought to be closely connected to the physical environment inside the mixing layer. Hence, the simulation results show that aluminum afterburning in EBX charges is strongly dependent on the mixing intensity, which is established by instabilities through shock-mixing layer interaction. Mixing intensity in its turn varies with HoB, as the shock propagation pattern is different for all HoB, indicating that in order to achieve maximum effect from aluminum inclusion to an explosive, HoB must be considered as a parameter.