Objective Hydrogen leakage in a long-distance pipeline within a tunnel can result in hydrogen accumulation, creating a potential hazard of ignition and explosion. Investigating the leakage and dispersion laws of hydrogen in tunnels offers critical insights into accident prevention and emergency response, contributing to improved safety in pipeline transport.

Method A numerical model was established based on the design parameters of a hydrogen pipeline in China. Computational fluid dynamics simulations were carried out for three accident cases with leakage hole diameters of 10.0 mm, 12.5 mm and 15.0 mm using FLUENT software. The leakage and diffusion process and volume fraction distribution of hydrogen in the tunnel were studied. A leakage point location model was established.

Result After the leakage, hydrogen mainly accumulated at the top of the tunnel. The volume fraction showed a Gaussian distribution in the horizontal direction and obvious stratification in the vertical direction. Over time, some of the hydrogen that had leaked moved downstream, while the rest stayed in the formed hydrogen layer, leading to a localized increase in hydrogen volume fraction. The volume fraction field of hydrogen in the tunnel after the leakage had a self-similarity that did not depend on the spatial size of the tunnel and the amount of leakage. Based on the self-similarity, a mathematical model of leakage point location was established, which could be applied to the working conditions of different tunnel sizes and leakage amounts (leakage pressure and hole diameter). The leakage point location and leakage aperture estimation were achievable through the model, with a positioning accuracy of up to 4.4% and an aperture estimation error of ≤15%.

Conclusion The study of hydrogen leakage and dispersion in the tunnel can provide a basis for the layout of leakage monitoring and hydrogen depletion devices. The leakage point location model enables rapid prediction of accident scenario evolution and formulates disposal measures.