Study of the effects of leakage volume and blockage ratio on the liquid hydrogen leakage diffusion behavior in a tunnel

Liquid hydrogen is widely used in various fields, but its leakage and diffusion behavior can form large-scale flammable and explosible clouds, posing significant safety hazards in confined environments. This study conducts three-dimensional transient numerical simulations to investigate the influence of leakage volume and blockage ratio on liquid hydrogen diffusion in tunnel. The results show that increased leakage volume significantly enlarges the explosible hydrogen cloud, reaching 174.7 m 3 , 288.3 m 3 , and 387.9 m 3 at 20 s for leakage volumes of 30 L, 60 L, and 90 L, respectively. The hydrogen cloud exhibits typical ground-hugging and wall-climbing behavior due to low temperature and density variations. Blockage ratio strongly affects the spatial distribution and mixing characteristics of hydrogen. While a high blockage ratio (α = 0.6) enhances early turbulence and accelerates mixing, it later induces backflow zones and stagnation effects, reducing diffusion efficiency and lowering average concentration by 50 % at 20 s. Additionally, time-resolved analysis reveals that explosive risk evolves rapidly within the first 15 s. This study provides a quantitative basis for the diffusion evolution characteristics and risk assessment of liquid hydrogen in tunnel, which has important engineering guiding significance. • Diffusion of liquid hydrogen leakage in tunnels is investigated. • Explosible cloud volume increases to 387.9 m 3 as leakage volume increases. • Higher blockage reduces cloud concentration and intensifies backflow. • This study provides quantitative data for hydrogen risk in semi-enclosed tunnels.