Afterburn Ignition Delay and Shock Augmentation in Fuel Rich Solid Explosives

Abstract

We present experimental and computational results that explain some aspects of measured energy release in explosions of unconfined trinitrotoluene [TNT, C 6 H 2 (NO 2 ) 3 CH 3 ], and an aluminum-containing explosive formulation, and show how this energy release can influence shock wave velocities in air. In our interpretation, energy release is divided into early, middle, and late time regimes. An explanation is provided for the interdependence of the time regimes and their influence on the rate at which energy (detonation/explosion and afterburn) is released. We use a merging of the thermodynamic and chemical kinetic processes that predicts how chemical kinetics may determine the time delay of the afterburn of combustible gases produced by the initial detonation/explosion/fast reaction. The thermodynamic computer code CHEETAH is used to predict gaseous and solid products of early time energy release, and a chemical kinetic reaction mechanism (CHEMKIN format) is used to describe the subsequent afterburn of the gas phase products in air. Results of these calculations are compared with field measurements of unconfined explosions of 2 kg charge weights of TNT and an aluminum-containing explosive formulation.

Characterization of the Mixing Layer Resulting from the Detonation of Heterogeneous Explosive Charges

“…For instance, experiments undertaken by McNesby et al [44] resulted in late-time fireball sizes of ∼2 m for a 2 Kg TNT homogeneous explosive charge, which translates to about 30 charge radii, and is comparable to the simulations undertaken in [13] for TNT. For NM, the fireball size is ∼15 charge radii (Fig.…”

Near field optical characterization of explosions

“…Because the emissivity is usually not known for the body under study, it is assumed to be wavelength independent (grey-body assumption) and therefore can also be factored out [8]. For the explosives C-4 and TNT, this is usually a reasonable assumption [9].…”

Chemical Imaging of Explosions – Mapping BO2 Light Emission

“…High-speed framing cameras have been used for decades to produce movies that help to visualize detonationsa nd explosions [1].W hile the detailed movies of these events can be qualitativelyi nformative, retrievingv ariables such as pressures, temperatures, and chemical species concentrations is difficult [2,3].R ecently,s ome success has been realized imaging fireball surface temperatures and peak shock pressures from small-to medium-sized explosions by careful manipulationo fi maging parameters [4].T hese efforts enable peak pressure and temperature "maps" to be produced as the explosion proceeeds [4].I nt his paper, this technique is extended to mapping of chemicals pecies arising from borono xidation during ab allistically initiated explosion.…”

“…Severalm etals and metalloids [e.g.,A l( aluminum),B (boron), Si (silicon)] may be added to propellants and explosives to increase energy [5].F or example, Equation (1), Equation (2), and Equation (3) showt he combustion energies (enthalpy of combustion, DH c ), in kiloJoules (kJ) per mole (mol) and kJ per gram (g) of fuel for the oxidation reactionsofB,Al, and Si, respectively.The combustion enthalpy of trinitrotoluene [TNT,C 7 H 6 N 3 O 6 ,E quation (4)] is also shown for comparison [ 6]. Because of the significant gaini nc ombustion energy (weight basis, relative to TNT) predicted by combustion calculations, boron has received considerable attentiona sa n additive to explosivea nd propellant mixtures [7].H owever, practical thermodynamica nd physical properties inhibit realization of this ideal [ 8].I nareview article, Yeha nd Kuo [7] summarized two-stage boronp article combustiona nd measured burn times.…”