Quantifying Momentum Transfer Due to Blast Waves from Oxy-Acetylene Driven Shock Tubes

Shock tubes have been widely used since the 1950s to study physical phenomena such as shock waves, combustion chemistry, and the response of materiel to blast loading. Recently, laboratory-scale shock tubes driven by oxy-acetylene were described. It was estimated that these shock tubes would not have a significant “jet effect” of expanding gases following the shock front because the combustion reaction is initiated at ambient pressure, and the molar volume of the products is less than that of the reactants. In this study, the transfer of momentum from a shock wave and expanding gases generated by oxyacetylene laboratory scale shock tubes to a solid object was quantified using high speed video (20,000 frames per second). A golf ball (diameter 42.7 mm, mass 0.0454 kg) was placed at the opening of a 27 mm diameter shock tube. The golf ball reached a peak acceleration of 478 g and a peak momentum of 1.2 kg m/s about 1 ms later. Similarly, a hollow aluminum sphere (diameter 101.6 mm, mass 0.240 kg) was placed at the opening of a 79 mm diameter shock tube. The sphere reached a peak acceleration of 1374 g and a peak momentum of 4.5 kg m/s about 2 ms later. In each case, most of the momentum transfer was due to the shock wave itself. The results support previous estimates that the oxy-acetylene shock tube design does not produce a significant “jet effect” of expanding gases or add significant loading to a test object.