Although liquid hydrogen provides high energy density and clean combustion, it poses significant safety risks due to its low boiling point, high diffusivity, and flammability. Therefore, addressing the safety challenges associated with large-scale liquid hydrogen leaks is essential for operational safety and risk management in hydrogen infrastructure, particularly in large-scale storage areas. This study investigates the dispersion characteristics of hydrogen vapor clouds and subsequent fire hazards following catastrophic leakage events, providing critical insights into safety implications under diverse environmental conditions.
A numerical model based on the fire dynamics simulator (FDS)—an advanced computational fluid dynamics tool developed by the U.S. National Institute of Standards and Technology—was developed. The applicability and accuracy of FDS in hydrogen safety simulations were systematically validated through comparisons with experimental data, quantitative error analysis, and cross-validation using peer studies. The simulations examined leakage scenarios involving evaporation, vapor dispersion, and fire development, incorporating fluid dynamics, phase change, combustion, and thermal radiation processes. Environmental factors such as overhead obstructions and solar radiation were also considered. The leakage source was modeled as a liquid hydrogen storage tank located at the center of a large-scale storage area. The lateral dispersion behavior of the hydrogen cloud under varying wind speeds and its impact on structures located off the downwind direction were analyzed. Subsequently, three comparative scenarios were established: a baseline case, a case with overhead confinement, and one with solar radiation. The effects of ceiling obstructions and solar heating on hazardous exposure times and cloud dispersion were evaluated. Moreover, the fire development and potential hazards in the vicinity of the storage area following immediate ignition after leakage were examined.
Simulation results indicated that: (1) Buildings located offset from the main wind direction were not affected by the lateral dispersion of the flammable hydrogen cloud. (2) The ceiling structure suppressed the vertical dispersion of the hydrogen cloud during the initial leakage phase and increased the horizontal transport rate, leading to a large gas-to-ground contact area and a prolonged hazardous exposure duration in near-field regions, which resulted in an increase in hazardous exposure time at Building 2 by 5s. (3) Solar radiation played a minimal role in the early-stage evaporation and dispersion of liquid hydrogen. Its thermal effect grew with time, serving to prolong the hazardous exposure time at building facility 2 by 12 s through accelerated cloud dispersion, with a corresponding delay in far-field arrival due to enhanced dilution. (4) In the event of ignition, the liquid hydrogen fire developed extremely rapidly, reaching a flame height of 30m and a lateral spread of 15 m within 9s; the core flame temperature exceeded 700℃. In the simulated fire scenario, the thermal radiation intensity in the ceiling monitoring area consistently exceeded the safety threshold. The thermal radiation intensity exceeded 12.5kW/m2, accounting for over 70% of the total simulation time, potentially causing structural damage such as steel failure and concrete spalling.
Quantitative studies on overhead confinement and solar radiation provide new insights into the potential risks of hydrogen facilities in complex environments, while research on the dynamic characteristics of accidental fires offers valuable information for the prevention of daily fires and the development of appropriate strategies to suppress fires.
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