Objective To explore the blending mechanism of natural gas and hydrogen under different physical property parameters during their co-transportation.

Method Based on transient turbulence model, multicomponent flow model, and multi-dimensional evaluation model, pipeline models including multi-dimensional T-type, embedded T-type and embedded L-type pipelines were established. The focus was on investigating the hydrogen blending process and its distribution patterns under varying pipeline parameters and gas operating conditions.

Results When the inner diameter of the hydrogen injection pipeline was increased from 15 mm to 45 mm, the hydrogen volume fraction at 2 meters downstream from the blending point in the upper part of the main pipeline increased from 11% to 23%. When the inner diameter of the main pipeline was decreased from 120 mm to 80 mm, the hydrogen volume fraction at 2 meters downstream from the blending point in the upper part of the main pipeline increased from 16% to 20%. A comparison between the optimized and conventional models demonstrated that, in the embedded L-type pipeline, no stratification was observed at the cross-sections 1.5 m to 2.0 m from the blending point.

Conclusion Stratification becomes more pronounced with larger hydrogen injection pipe diameter, higher hydrogen blending ratio, smaller main pipe diameter, or lower gas velocity. Among these factors, the inner diameter of the hydrogen injection pipeline has the most significant impact on stratification. The embedded L-type pipeline is the most advantageous in the co-transportation of hydrogen and natural gas.