Numerical investigation of the leakage and diffusion characteristics of hydrogen-blended natural gas in long-distance pipelines

This paper uses Fluent software to create a 3D leakage model for hydrogen-blended natural gas pipelines and analyzes how hydrogen blending ratio (HBR), soil type, and leakage hole shape affect gas dispersion. Results show that hydrogen and methane have different concentration distributions in soil: hydrogen forms an 'n' shaped distribution while methane forms an 'M' shaped distribution, with higher hydrogen concentrations observed further from leakage holes. HBR has a minimal effect on diffusion; higher HBR leads to lower concentrations at saturation. Soil type significantly impacts diffusion, with sandy soils showing higher gas concentrations than clay. Slit-type holes result in faster concentration saturation compared to square-type holes. Increasing the number of leakage holes from two to four enhances concentration differences and accelerates diffusion. The optimal axial spacing for fast diffusion is 200 mm. These findings support monitoring and risk assessment for hydrogen-blended natural gas pipelines.