Effects of scale on internal blast measurements

Abstract

This paper presents a comparative study between large and small-scale internal blast experiments with the goal of using the small-scale analog for energetic performance evaluation. In the small-scale experiment, highly confined explosive samples <0.5 g were subjected to the output from a PETN detonator while enclosed in a 3-liter chamber. Large-scale tests up to 23 kg were unconfined and released in a chamber with a factor of 60,000 increase in volume. The comparative metric in these experiments is peak quasi-static overpressure, with the explosive sample expressed as sample energy/chamber volume, which normalizes measured pressures across scale. Small-scale measured pressures were always lower than the large-scale measurements, because of heat-loss to the high confinement inherent in the small-scale apparatus. This heat-loss can be quantified and used to correct the small-scale pressure measurements. In some cases the heat-loss was large enough to quench reaction of lower energy samples. These results suggest that small-scale internal blast tests do correlate with their large-scale counterparts, provided that heat-loss to confinement can be measured, and that less reactive or lower energy samples are not quenched by heat-loss.