A series of field explosion experiments of hydrogen-air mixtures were carried out. The mixtures were accumulated in plastic greenhouses and ignited by electric spark or by high explosive detonation. The sound generated by these explosions were measured over a wide range. The sound pressure waveform and frequency spectrum were compared among the cases of spark ignition and high explosive ignition of hydrogen-air mixtures, together with the cases of high explosive explosion in free air, and the relationship between the peak sound pressure/frequency and scaled distance was revealed. It was found that the cases of high explosive ignition of hydrogen-air mixtures and the cases of high explosive explosion in free air showed almost the same sound pressure characteristics, but the cases of spark ignition showed significantly different sound pressure characteristics.
In this study, nano-CuO prepared via mechanical grinding was applied to ammonium perchlorate (NH4ClO4, AP)/hydroxyl-terminated polybutadiene (HTPB) propellant. The catalytic effect of nano-CuO was investigated by thermogravimetric analysis/differential scanning calorimetric techniques. The combustion behaviour of the AP/HTPB propellant was measured at atmospheric pressure using the strand burner method. In comparison with that of the blank propellant, the high-temperature decomposition peak of nano-CuO-AP/HTPB shifted from 661 to 630 K, the propellant’s apparent decomposition heat increased from 1251 to 2313 J･g-1, and the Gibbs free energy of the propellant decreased from 184.2 to 174.8 kJ･mol -1. Simultaneously, the combustion rate of the propellant at atmospheric pressure increased by approximately 20.8 % from 1.25 to 1.51 mm･s -1, and its combustion intensity was remarkably enhanced in the presence of nano-CuO. Experiment results demonstrate that the catalytic activity of nano-CuO on the AP/HTPB propellant is superior to that of bulk CuO, which can be attributed to its high catalytic activity resulting from its small size and large specific surface area.
Mitigation of a blast wave from a straight tube using glass beads was evaluated to examine blast-wave mitigation by glass beads on a tube floor. Glass beads of 0.6 mm or 3.0 mm diameter were installed on the floor of a square, 330-mm-long straight tube with cross-sectional area of 30 × 30 mm2. Arrangement of the glass beads on the tube floor was varied in four ways. The glass bead layer thickness was 5.0 mm, so that the glass beads did not contact with the test explosive. One end of the tube was closed. A specially designed small detonator that contained 100 mg lead azide was ignited near the closed end of the tube as the test explosive. The dependence of mitigative effect on the glass bead diameter and the arrangement was evaluated by measuring the blast pressures outside the tube. The glass beads mitigated the blast wave. The “without glass beads equivalency” analysis revealed that small-diameter glass beads absorbed more energy than large-diameter beads did. The absorbed energy was approximately 40 % of the explosion energy. Results of this study also revealed that the glass beads, which were not near the explosive, are more important for blast mitigation than a water layer on the tube floor.