Numerical Simulation of Hydrogen-Blended Natural Gas Pipeline Leakage and Dispersion Based on ANSYS Fluent

Hydrogen blending into natural gas pipelines is considered a practical transitional pathway for large-scale hydrogen transportation and sustainable utilization of existing gas-energy infrastructure. However, hydrogen addition changes the physical properties, in-pipe distribution, leakage behavior, and post-leakage safety risks of the gas mixture. In this study, ANSYS Fluent was used to establish a three-dimensional T-junction pipeline mixing–leakage model and a two-dimensional open-environment dispersion model. The effects of hydrogen blending ratio, leakage-hole diameter, and ambient wind speed on leakage dynamics and hazardous gas-cloud evolution were investigated. The results show that local hydrogen enrichment and gravity stratification occur after T-junction mixing, with hydrogen preferentially accumulating in the upper region of the main pipe. Increasing the hydrogen blending ratio enhances gas-cloud dispersion and buoyancy-driven rise. Under a wind speed of 5 m/s and a leakage-hole diameter of 10 mm, increasing the hydrogen blending ratio from 20% to 40% enlarges the dispersion range by approximately 35%. Leakage-hole diameter has the strongest effect on initial leakage intensity, with the simulated leakage velocity increasing by approximately 96 times when the hole diameter increases from 1 mm to 10 mm. Increasing ambient wind speed promotes downwind cloud extension while suppressing lateral dispersion. These findings provide guidance for leakage-risk identification, monitoring layout, safety-distance design, and emergency response for hydrogen-blended natural gas pipelines.