Research on the flow field characteristics of hydrogen-blended natural gas pipeline under unstable mixing conditions

Significant differences in key physical properties, such as density, between methane and hydrogen lead to dynamic changes in the flow characteristics of hydrogen-blended natural gas within pipelines, posing substantial impacts on the engineering design and operational safety of pipelines. This is a critical issue that must be clarified for the development of hydrogen storage and transportation technology. Therefore, this study systematically investigates the flow characteristics of hydrogen-blended natural gas in typical pipe segments under different hydrogen blending ratios by combining experiments and numerical simulations. An experimental platform was established to obtain the flow field distribution in bent pipes, and an optimal turbulence model for computational fluid dynamics simulations was selected. The results indicate that the flow parameters of hydrogen-blended natural gas remain generally stable during pipeline transportation. Under unstable mixing conditions, the response time to changes in the hydrogen blending ratio follows the order: pipeline center > pipeline wall and inner surface of the bent pipe > outer surface of the bent pipe. When the flow velocity change reaches 5 m/s or the hydrogen blending ratio change reaches 8%, pressure fluctuations at the bent pipe exceed those in other pipe segments. Simulation data show that pressure fluctuations within the pipeline remain below 1000 Pa. This study provides key theoretical and data support for the stable operation and optimized design of hydrogen-blended natural gas pipeline systems.