Risk Assessment of Liquid Hydrogen-Powered Unmanned Aerial Vehicles Using the PHAST Program

Hydrogen energy, one of the eco-friendly energy sources, is gaining attention as a solution to environmental problems. Liquid hydrogen (LH₂) is considered one of the key solutions for powering long-distance large-scale transportation systems, such as large ships and aircraft. Consequently, unmanned aerial vehicle (UAV) utilizing hydrogen fuel cells have attracted attention due to their numerous advantages and promising future. However, ensuring safety is essential, as hydrogen has a high potential for large-scale damage in the event of an explosion accident.<br/> In this study, virtual accident scenarios, including leakage and catastrophic rupture, were established to assess the effects of fire and explosion caused by pipeline leaks in liquid hydrogen systems. The 2D simulation program DNVⓇ PHAST v.8.9 was used to analyze the vapor cloud explosion (VCE), jet fire profile, impact distance, and the 100% lower flammability limit (LFL) range. As a result, in the leakage scenario, a 100% LFL zone and jet fire were observed when no ignition source was present. In the catastrophic rupture scenario, a pool fire and VCE occurred. The maximum radiative heat from the jet fire was measured at 3.04 kW/m², which did not exceed domestic evacuation safety standards, suggesting a low likelihood of significant harm to humans. It was also confirmed that changes in initial leakage conditions and weather conditions could influence fire and explosion impacts. This study provides critical data that can contribute to establishing safety management standards and serves as a reference for accident prevention and response strategies related to liquid hydrogen-powered unmanned aerial vehicles in the future.