The dependence of Ammonal detonation performance on cylinder test scale

Abstract

For a detonation to propagate steadily, the lead shock must be supported by energy release from the chemical reaction zone. Flow divergence cools the flow behind the compression shock, slowing chemical reactions and reducing the available energy to drive the detonation forward. This results in the diameter effect and eventually detonation failure as charge size is reduced. Similarly, the energy available to perform work on adjacent materials in the product flow tends to decrease with charge size. The performance of non-ideal explosives such as ammonium nitrate blended with aluminum powder (Ammonal) are particularly sensitive to flow divergence. In this study, the effect of flow divergence on Ammonal performance is investigated through application of an analytic method to analyze cylinder expansion (CYLEX) test wall velocity profiles for tests with inner diameters of 12.7 mm up to 76.2 mm. For these tests, the detonation velocity, detonation product isentropes, and heat of detonation are reported. In addition, analysis of the velocity profiles is shown to reveal an experimental measurement of the Rayleigh line, which agrees well with the theoretical Rayleigh line for all experiments. Reaction zone times are inferred using this feature.