The 10th Asian Symposium on Computational Heat Transfer and Fluid Flow ( ASCHT2025)

Hydrogen is recognized as a clean and efficient energy, and the transportation of hydrogen energy is a key factor constraining its industrial development. Blending hydrogen into existing high-pressure natural gas pipelines is regarded as the most economical transitional solution. However, due to hydrogen’s high diffusivity, strong flammability, and low ignition energy, the risks of leakage, auto-ignition, and explosion are significantly increased, while the underlying mechanisms remain complex and insufficiently studied. This study investigates the entire process of “leakage–auto-ignition–explosion” through multi-scale numerical simulations and mechanistic analysis. First, a leakage model is established to reveal flow evolution and flammable cloud formation under different hydrogen blending ratios, pressures, and orifice sizes. Second, a reduced chemical mechanism and ignition criteria are applied to analyze critical conditions for auto-ignition, clarifying the inhibitory effect of methane and the possibility of wall-induced ignition under high hydrogen concentration scenarios. Finally, a thickened flame model is employed to simulate ignition and explosion of typical leakage clouds, yielding overpressure propagation, temperature evolution, and damage mechanisms on station facilities. The findings provide theoretical support for safety risk assessment and prevention strategies in high-pressure hydrogen-blended natural gas pipelines.