To address concentration stratification during pipeline transportation of hydrogen?blended natural gas and improve mixing efficiency over short distances, a multicomponent turbulent?flow model was established using computational fluid dynamics. The mixing characteristics, flow?field evolution, and pressure loss of three spiral static mixer structures?right?handed blades, crossed blades, and crossed perforated blades were compared. The coefficient of variation and mixing uniformity were used as quantitative indicators for comprehensive evaluation. The results show that the crossed perforated?blade structure satisfies industrial mixing requirements (uniformity≥95%) within 2 m through the synergistic effects of swirl, jet flow, and secondary flow. The mixing uniformity reaches 99.66% at 5 m, with a concentration?mixing influence factor of 9.14 and a pressure loss of 189.3 Pa. It is concluded that the synergy among swirl, jet flow, and secondary flow is the core mechanism for achieving efficient short?distance mixing. The crossed perforated?blade structure significantly improves mixing efficiency while maintaining low?loss transportation. The findings provide a reference for the selection of static mixer structures.

The forward and reverse transportation simulation model was established by using SPS simulation software to simulate the forward and reverse operation process of A?Sai crude oil pipeline at low throughput. The change law of the oil temperature along the pipeline during the process of forward and reverse transportation is studied. The results show that the oil temperature along the pipeline decreases gradually under the steady state of forward transportation. The oil temperature drops first and then increases at the beginning of the reverse transportation, and then drops gradually after reaching the steady state.The oil temperature at the reverse inlet station decreases first and then increases slightly, and finally tends to be stable. The lowest temperature of crude oil in the process of forward and reverse transportation is the arrival temperature when the remaining crude oil is completely pushed out of the pipeline. In addition, the influence of inverse throughput on oil temperature drop during the inverse transportation was analyzed. The higher the inverse throughput is, the higher the lowest oil temperature in the process of inverse transportation is, and the faster the stable state of inverse transportation reaches. The temperature change of forward and reverse transportation obtained by SPS simulation analysis can provide certain basis for making the forward and reverse transportation scheme of A?Sai pipeline.

The crude oil produced by oil wells contains sediment, scale and other particles, which are deposited together with the wax in the process of crude oil pipeline transportation. It leads to a decrease in pipeline throughput, and may cause pipeline blockage and affect the safety of transportation in severe cases.The yield stress test and microscopic characteristic experiments show that there is a critical scale containing ratio in wax deposits of the influence of calcium carbonate scale on the strength of wax deposits. And it is found that the wax deposits containing scale will increase the breaking force on the wax layer and the pigging efficiency of the pig through the indoor pigging experiment of polyethylene pipeline. Based on the data of pigging experiment, a prediction model of pigging efficiency was established by using the π theorem. The model was validated by indoor experiments and third?party literature experimental data.