Numerical simulation of hydrogen leakage diffusion in a small underground garage with different parking space modes

In recent years, hydrogen energy has been widely applied in various industries, but it may also bring a series of safety concerns. Especially in confined spaces like underground garages, where high-pressure hydrogen leaks can potentially cause combustion or explosions. To address this, this paper integrates numerical calculations and theoretical analysis to simulate the process of continuous high-pressure hydrogen leakage from hydrogen-powered vehicles within underground garages. Through investigating the influence of various parking space modes and the number of ventilation openings under mechanical ventilation conditions on hydrogen diffusion and distribution, it was discovered that, during the initial stages of leakage, the 2-parking space mode exhibited a slightly higher overall explosion risk in comparison to the 3- and 4-parking space modes. Notably, after 15 s, the 4-parking space mode shows the highest global explosion risk, while the 2-parking space mode consistently demonstrates the highest local explosion risk in the overhead space. Under mechanical ventilation, the number of ventilation openings significantly reduces hydrogen concentration over time. Specifically, after leakage cessation, increasing ventilation openings efficiently shortens the time required for hydrogen levels to drop to safe limits within the garage. The findings of this study can provide important references for the safety design of hydrogen fuel cell vehicle garages.