Additional afterburning energy value to simulate fully confined trinitrotoluene explosions

Abstract

Euler-Lagrange software packages are commonly employed in the analysis and design of chambers subjected to internal detonations of high explosives because they allow modeling the interaction between high-explosive gas products, air, liquid, and structures. In general, the expansion of high-explosive products is modeled by the Jones-Wilkinson and Lee equation of state, and additional extension methods such as the Miller or the additional energy release extensions are used to model the afterburning energy which is released after the detonation. These extension methods require that the additional energy by unit mass is predefined. Although the difference between the heat of combustion and the heat of detonation provides a specific value for the additional energy, for example, 10.01 MJ/kg TNT for trinitrotoluene charges detonated inside of chambers with rich oxygen, this value is generally inappropriate if high-explosive gas products and air are modeled separately, that is, by the Jones-Wilkinson and Lee equation of state and the ideal gas equation of state, respectively. This article explains how to determine an appropriate value for the specific additional energy value for use in the commercial software package AUTODYN for more reliable predictions of the quasi-static gas pressure in fully confined chambers subjected to trinitrotoluene explosion. The procedure detailed in this article can be applied to any kind of chamber geometries and chamber materials. A simplified chart for the afterburning energy as a function of the charge mass density is derived. The proposed approach in predicting the quasi-static gas pressure is validated with the quasi-static gas pressure described by the Unified Facilities Criteria's guideline and some experimental tests. A procedure to determine the additional afterburning energy that should be employed for highly deformable chambers is also explained.

On the effectiveness of ventilation to mitigate the damage of spherical membrane vessels subjected to internal detonations

“…From Figure 7, it is observed that the QS gas pressure that was obtained for the FC case and the 3D model matches closely with that given by UFC (Table 1) if an appropriate additional afterburning energy value is used (Hernandez et al, 2016). Similarly, the gas pressure for the PC condition agrees well with the pressure component that is suggested by Anderson et al (1983), which was obtained from adjustment of experimental data, and it is reasonably similar to the simplified triangular gas pressure component suggested by the UFC (which was also obtained from experimental data, but based on a simplified triangular curve).…”

“…W/V vessel > 0.387 kg-TNT/m 3 , Table 1) and should show a final QS temperature of 2800 K in agreement with the chemical equilibrium (Edri et al, 2013). Nevertheless, it can be observed that the QS temperature that is calculated from the 3D model disagrees with those from the chemical equilibrium approach because gases are modeled by independent EOS and are not described such as a unique gas that should be modeled by a variable gamma ideal gas EOS (Edri et al, 2013;Hernandez et al, 2016). Ventilation reduces the exposition time that chambers are subjected to high temperatures, generating a flash temperature and avoiding that the final QS temperature is reached.…”

“…In general, the arrival times of secondary SWs involve a certain degree of uncertainty. As previously mentioned, the way that the afterburning energy is released can change the arrival time, and the peak reflected pressure associated with each SWs (Hernandez et al, 2016).…”

On the effectiveness of ventilation to mitigate the damage of spherical chambers subjected to confined trinitrotoluene detonations

“…In fact, the pressure time-history, which acts on chamber walls subjected to fully or partially confined HE detonations, is commonly described by three components. In this context, the three pressure components that are generated by confined HE detonations that occur on spherical chambers have been described from theoretical derivations (Abakumov et al, 1984; Belov et al, 1986; Zhdan, 1981), numerical simulations (Donahue et al, 2013; Dong et al, 2012; Hernandez et al, 2016; Li et al, 2008), and observed from experimental data (Adishchev and Kornev, 1979; Anderson et al, 1983; Belov et al, 1986; Beshara, 1994; Buzukov, 1980; Chan and Klein, 1994; Donahue et al, 2013; Dong et al, 2012; Hernandez et al, 2016; Karpp et al, 1983; Li et al, 2008). The first component is an impulsive component caused by the reflection of the first shock wave, which propagates supersonically from the detonation point until it reaches the chamber wall.…”