Study on drag reduction characteristics of air flow by injecting agent into the inner wall of pipe

Natural gas is essential to the low-carbon energy transition, making pipeline efficiency and drag-reducing technologies research priorities. This study developed novel drag-reducing agents (DRAs) by compounding oleic imidazoline (IM) with triethanolamine phosphate (P-TEA), triethanolamine (TEA), and sodium dodecylbenzenesulfonate (LAS). The composite DRAs underwent initial screening for film formation, followed by a systematic loop-test evaluation. The results demonstrate significant synergistic effects between IM and P-TEA or TEA, markedly enhancing drag reduction performance. The IM + 5% P-TEA system performed best, achieving a maximum drag reduction rate of 10.04% at a flow rate of 240 L/min (i.e. 345.6 m3/d), whereas LAS showed only a weak synergistic effect. The study further revealed that the drag reduction efficiency increases with the flow rate within a critical range and that atomized injection outperforms static pre-filming. The composites also exhibited considerable time-effectiveness. This work clarifies the drag-reducing properties of the composite agent and establishes the theoretical basis for efficient natural gas pipeline technology.