Blast Loading Profile of Gaseous Hydrogen in Confined Space Under Various Leak Conditions

Abstract Research on hydrogen facilities in the shipbuilding industry and on hydrogen fuel ships and carriers is growing due to the depletion of fossil fuels and the increasingly strict regulation of environmental pollution. Compared with hydrocarbon-based fuels, hydrogen fuel has low minimum ignition energy and a wide-ranging flammability limit. Therefore, before utilizing hydrogen energy, hazard assessment studies of hydrogen leakage and explosion must be performed to ensure safety. It is hazardous to the release of gaseous hydrogen into confined spaces, such as storage and engine rooms of ships, because the hydrogen gas cloud, which is less dense than air, stagnates and accumulates near the ceiling. The main objective of this study is to examine the effects of gaseous hydrogen leakage conditions in confined spaces on the behavior of flammable gas cloud and blast loading profile. To analyze hydrogen gas cloud behavior, hydrogen release experiments were conducted in a 1.0 m × 1.0 m × 3.0 m enclosure at various leak nozzle heights (0.3, 1.5, and 2.7 m) and leak rates (100, 200, and 300 L/min). The results of hydrogen leakage experiments, the flammable gas cloud volume were found to increase with increasing leakage rate and decreasing leakage nozzle height. Due to the lack of the number of concentration sensors, there was a limit to the analysis of all the concentration field of hydrogen in the enclosure. All flammable concentration fields in the enclosure were evaluated and compared using FLACS, the computational fluid dynamics simulation software. In addition, the effects of ignition heights on hydrogen blast loading were analyzed using FLACS. The simulation revealed that a high hydrogen leak rate and a far leak nozzle-ceiling distance tends to result in a large gas cloud volume, which in turn results in high peak pressure and impulse. The highest overpressure and impulse were approximately 5 barg and 39 kPa·s, respectively. These results suggest that in confined spaces, equipment with high potential for hydrogen leakage (e.g., pipes) should not be designed near the ground. This paper thus contributes to the design standard for hydrogen storage facilities in confined spaces (e.g., ships) and lays the foundation for establishing a standard for marginal safety blast walls for protection from hydrogen explosions.