Study on mixing characteristics of coaxial shear static mixers in long-distance hydrogen-blended natural gas pipelines

Static mixers are key equipment for improving the uniformity of hydrogen and natural gas mixing within pipelines. This work develops a coaxial shear static mixer for long-distance high-pressure gas pipelines via numerical simulations. It explores how cavity quantity impacts flow fields and mixing efficiency to determine the optimal structure, and discusses the influences of gas flow velocity and hydrogen blending ratio on mixer performance. Its mixing capacity is also compared with the KSM static mixer. The results show cavity count dominates overall performance: 25 cavities deliver the best mixing uniformity with an 8D effective mixing length. Gas velocity and hydrogen proportion barely change mixing uniformity yet greatly alter pressure loss. The coaxial shear mixer cuts pressure drop by 52.99% versus KSM mixers under identical working conditions, possessing prominent low-pressure-loss merits. This research offers reliable guidance for designing and choosing static mixers for long-distance hydrogen-mixed gas pipelines.