Mixing Behavior of Natural Gas and Hydrogen in a High-Efficiency Vane (HEV) Static Mixer

Blending hydrogen into natural gas pipelines is considered a practical approach for enabling large-scale hydrogen transport. Achieving a homogeneous hydrogen–natural gas mixture requires structural optimization of static mixers. In this study, a three-dimensional mixing model of natural gas and hydrogen within a HEV static mixer was developed using computational fluid dynamics, and its accuracy was validated against experimental data. A systematic investigation was conducted to evaluate the effects of vane angle (α), hydrogen injection strategy, vane number (n), and vane array spacing (ξ) on mixing uniformity and pressure drop. The results indicate that both mixing uniformity and pressure drop first increase and then decrease with increasing vane angle: at α = 60°, regions of intense turbulence are most concentrated, whereas at α = 120°, turbulent zones extend further downstream. Regarding the hydrogen injection strategy, counter-flow injection generates stronger flow disturbances, resulting in superior mixing performance. Increasing the number of vane arrays enhances both mixing uniformity and total pressure drop. Smaller vane array spacing promotes higher mixing uniformity over a shorter axial distance while maintaining a lower pressure drop. Based on these findings, the recommended HEV mixer configuration is α = 60°, n = 4, and ξ = 1D, combined with a reverse hydrogen injection strategy.