Ignition margin of fuel-air explosive cloud

This study focuses on the scenario in which the secondary initiation charge column is positioned at the periphery of the cloud formed subsequent to the dispersion of the fuel-air explosive (FAE). It conducts in-depth research on the initiation margin of the cloud. A prototype filled with 12.5 kg of colud explosive was meticulously designed. The maximum radius of the cloud was precisely determined through a series of dispersion tests. A 1-kg-HMX-based explosive was employed as the secondary detonator explosive. Through comprehensive experimental investigations, including high-speed and overpressure tests, the relationship between the distance of the charge column from the edge of the cloud and the initiation state of the cloud was established, and the distance threshold was accurately determined. Using the peak overpressure at the edge of the cloud as an index to measure the initiation margin, the threshold of the peak overpressure at the cloud edge that satisfies the initiation conditions of the cloud was investigated via empirical formulas and numerical simulations. The peak overpressure was further verified based on the critical energy flow criterion. The results indicate that placing a 1-kg-HMX-based explosive at the periphery of the cloud can also trigger the cloud to detonate, provided that the distance from the cloud edge does not exceed 0.5 m. When the energy of the secondary initiation charge column is adequate to trigger stable detonation of the cloud, the location of the secondary detonator explosive exerts minimal influence on the detonation overpressure. To guarantee the initiation performance of the cloud, the peak overpressure at the edge of the cloud generated by the secondary detonator explosive should not be lower than 5 MPa. This study takes into account the stringent conditions for cloud initiation, and the research findings can offer support for the design of the secondary initiation charge columns.