Explosion overpressure behavior and flame propagation characteristics in hybrid explosions of hydrogen and magnesium dust

The explosion risk of a hybrid mixture of hydrogen and magnesium dust is relatively high during the production of magnesium-based hydrogen storage materials and industrial magnesium products. To explore the explosion characteristics of a hybrid hydrogen/magnesium dust mixture, the overpressure variation and flame propagation characteristics of the hybrid hydrogen/magnesium dust mixture in a 5-L semi-closed explosion duct were experimentally studied. The results show that the explosion pressure (P-ex) and the explosion pressure rise rate ((dP/dt)(ex)) of the hybrid hydrogen/magnesium dust mixture significantly increase only when the hydrogen concentration is greater than 10 %. The flame of a pure magnesium dust explosion mainly consists of the unburned zone, preheating zone, and combustion reaction zone. Compared with pure magnesium dust, the flame structure of the hybrid hydrogen/magnesium dust mixture explosion does not change significantly, but a red emission zone appears at the front of the preheating zone. Moreover, the range of the preheating zone is significantly larger compared to pure magnesium dust, and it increases with the hydrogen concentration. When the hydrogen concentration is low, the flame propagation speed of the hybrid hydrogen/magnesium dust mixture exhibits strong pulsation. The pulsation frequency of the flame propagation speed of the hybrid mixture explosion gradually decreases with the hydrogen concentration, but the average flame propagation speed continually increases. Based on the experimental results, the explosion mechanism of the hybrid hydrogen/magnesium dust mixture was analyzed from the perspective of reaction kinetics by numerical simulation.