Comprehensive performance analysis of static mixers used in hydrogen-blended natural gas

Static mixers play a vital role in ensuring the uniform mixing of natural gas (NG) and hydrogen, thereby reducing operational costs at gas transmission stations and enhancing transportation efficiency. This study, based on the design parameters of a section of the high-pressure Shaanxi–Beijing Gas Pipeline I, employs numerical simulations to compare the flow characteristics and mixing mechanisms of four types of static mixers: T-junction, Kenics, High-Efficiency Vane (HEV), and Coaxial shear. A hydrogen blending experimental platform was constructed, and experimental investigations were carried out to validate the strong agreement between numerical simulations and experimental data. The study explores the velocity distribution patterns and mixing behaviors of the different mixers and analyzes the effects of hydrogen blending ratios — ranging from 5% to 20% — on mixing uniformity and pressure drop. The Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is adopted to provide a comprehensive performance evaluation and ranking of the four mixers. The results indicate that the performance ranking from highest to lowest is: Coaxial shear mixer (Score: 0.84, Rank: 1), Kenics mixer (Score: 0.59, Rank: 2), HEV mixer (Score: 0.53, Rank: 3), and T-junction mixer (Score: 0.40, Rank: 4). Under identical operating conditions, the Coaxial shear mixer achieved the shortest distance required for complete uniform mixing (1D) and a relatively low pressure drop (5321.12 Pa), while the T-junction mixer required the longest mixing distance (43D) but had the lowest pressure drop (3033.99 Pa). This study provides experimental data for hydrogen-blended static mixers and offers methodological guidance for selecting static mixers in industrial applications.