Estimation of Explosive Energy Output by EXPLO5 Thermochemical Code

Abstract

Detonation velocity, detonation pressure, and detonation heat are usually used as a measure of explosive's performance. However, they do not answer the question how fast an explosive can accelerate the surrounding metal liner. A semi‐empirical solution to this problem was proposed by R. W. Gurney in 1943. In this paper we used thermochemical calculations to calculate energy of detonation products along the expansion isentrope and to estimate the Gurney energy and cylinder wall velocity from it. It was found that for the same degree of the products expansion, experimentally determined Gurney energy is systematically less than calculated detonation energy due to the energy losses. At about threefold expansion of the products, the detonation energy matches very well with an experimental Gurney energy.

Prediction of Cylinder Wall Velocity Profiles for ANFO Explosives Combining Thermochemical Calculation, Gurney Model, and Hydro‐Code

“…Our previous studies have shown that at the same expansion ratio, detonation energies calculated by EXPLO5 code are systematically ∼10% higher than the Gurney energies derived from experimental cylinder wall velocities [15, 16]. Similar results are reported also by Hardesty and Kennedy [17] and by Danel and Kazandijan [5] who used different thermochemical codes.…”

“…This partly explains the energy difference between the Gurney model and hydro‐code calculations. The results reported in [16], as well as the results shown in Figure 2, suggest that the overall energy losses accounts for about 10% of the total energy. The easiest way to take into account energy losses is to reduce calculated detonation energy in the Gurney equation (Eq.…”

“…It is also noticed [16] that for the same expansion ratio experimental Gurney energies are about 10 % lower than detonation energies calculated from EXPLO5’s expansion isentrope. Danel and Kazandjian [5] have shown that, despite the discrepancy, using the results of thermochemical calculations along with the hydro‐codes, gives good prediction of cylinder wall velocity.…”

“…Unfortunately, most of such empirical approaches are not accurate enough. It was shown in [15] that the Gurney velocity can be more accurately predicted from the detonation energy along the expansion isentrope, where detonation energy is calculated theoretically using thermochemical code EXPLO5 [15, 16]. Our analysis, based on a large number of reported experimental data [15, 16], as well as the work of Hardesty and Kennedy [17] and Danel and Kazandijan [5], has shown that experimental Gurney energy (which is obtained at V / V 0 =7) agrees well with the detonation energy calculated by thermochemical code at V / V 0 ≈3.…”

“…It was shown in [15] that the Gurney velocity can be more accurately predicted from the detonation energy along the expansion isentrope, where detonation energy is calculated theoretically using thermochemical code EXPLO5 [15, 16]. Our analysis, based on a large number of reported experimental data [15, 16], as well as the work of Hardesty and Kennedy [17] and Danel and Kazandijan [5], has shown that experimental Gurney energy (which is obtained at V / V 0 =7) agrees well with the detonation energy calculated by thermochemical code at V / V 0 ≈3. Hardesty and Kennedy [17] attributed this energy difference to the fracturing of the cylinder wall after it is strained to the point of rupture, so the detonation products leak out between the fragments and do not contribute to the value of the Gurney energy at larger expansion ratios.…”