CFD analysis of leakage and diffusion characteristics in the buried hydrogen-blended natural gas pipeline

Blending hydrogen into natural gas pipelines can affect their safety. Therefore, it is necessary to study the leakage and diffusion characteristics of hydrogen -blended natural gas (HBNG) pipelines. This paper establishes an integrated model of buried HBNG pipeline leakage and diffusion using programming for numerical simulation, and achieves the coupling of pipeflow-seepage-diffusion models. The PVT characteristics of the pipeline, concentration distribution, and hazard range of the underground and free space areas are studied. Effects of hydrogen blending ratio (HBR), soil permeability, and wind speed on leakage and diffusion characteristics are analyzed. The results show that the HBNG exhibits a larger pressure and flow rate fluctuation range after leakage but a lower mass flow rate and leakage mass flow compared to natural gas. With an increase in HBR, the risk index for the whole process also increases. The HBNG pipeline with 20% HBR has a higher underground pressure influence radius and underground hazard radius by 15.4% and 11.9% respectively, and the above -ground hazard height is 34.0% higher than the natural gas pipeline. In addition, the maximum hazard time is 33.3% faster. Increasing soil permeability significantly reduces the hazard range. Increasing wind speed dramatically reduces the hazard height. This study provides a transient computational model for the entire process of leakage and diffusion in the HBNG pipeline and offers theoretical guidance for the consequences of leakage.