摘要：

为探究成品油管道顺序输送甲醇的混油演化规律，本研究首次在国内开展了甲醇—汽油中试级顺序输送试验。试验系统设有透明观测段，可实时可视化混油界面形貌，并配备在线密度计以连续监测混油区内浓度变化。研究系统评估了管道运行长度、流速及输送顺序对甲醇—汽油混油长度发展的影响，并将结果与相同工况下汽油—柴油顺序输送试验进行对比，以揭示两种介质组合体系的共性与差异。
试验结果表明，在恒定流速下，甲醇推汽油和汽油推甲醇两种输送顺序的混油长度均随运行长度增加而增长，但增长率逐渐减缓，呈现非线性趋势，说明混油区扩展在长距离输送中趋于饱和。在固定运行长度下，当流速从0.8 m/s提高至1.5 m/s时，混油长度总体呈下降趋势，表明提高流速可通过增强湍流剪切与界面扰动有效抑制混油区发展。形貌观察显示，汽油—甲醇混油与汽油—柴油混油均呈均匀透明的扩散掺混状态，无分层或界面突变现象，证实了两种体系中因介质互溶性良好，湍流扩散均为主导混油机制。然而定量比较表明，所有试验条件下汽油—甲醇混油长度均明显短于汽油—柴油混油，这可归因于甲醇与汽油间较低的黏度差异及更快的分子扩散平衡速度。
汽油—甲醇混油与汽油—柴油混油在宏观扩散行为上表现出显著类比性：两者混油区均沿管道轴向对称发展，浓度分布从前行液体逐渐过渡至后行液体，与经典湍流扩散模型一致；两种体系中流速升高均使相同运行距离下的混油长度缩短，且变化趋势一致。这一类比性表明，现有汽油—柴油混油长度预测模型，可通过将试验测定的甲醇—汽油体系有效扩散系数代入模型框架进行修正，从而适用于汽油—甲醇混油长度的定量预测。本研究结果为甲醇在多产品成品油管道中的输送工程设计、运行优化及风险评估提供了重要的试验数据与理论指导，有助于推动甲醇作为清洁替代燃料在现有管道基础设施中的推广应用。

关键词: 甲醇, 汽油, 顺序输送, 混油, 中试试验

Abstract:

To investigate the mixing evolution during batch transportation of methanol in refined oil pipelines, a pilot-scale sequential transportation trial of methanol and gasoline was carried out. The experimental system was equipped with a transparent observation section for real-time visualization of the mixing interface morphology, along with online density meters to continuously monitor concentration variations within the mixed zone. The study systematically evaluated the effects of operational pipeline length, flow velocity, and transportation sequence on the development of methanol-gasoline mixing oil length. In addition, the results were compared with those from gasoline-diesel batch transportation under identical operating conditions to identify both common features and differences between the two liquid-pair systems.
Experimental results indicated that under a constant flow velocity, the mixing oil length increased with increasing operational length for both transportation sequences, namely methanol pushing gasoline and gasoline pushing methanol. However, the growth rate gradually declined as the distance extended, revealing a nonlinear trend and implying that the mixing zone expansion approaches a saturation state over long-distance transport. Under a fixed operational length, when the flow velocity was raised from 0.8 m/s to 1.5 m/s, the mixing oil length exhibited a general decreasing trend, demonstrating that higher flow velocities effectively suppress mixing zone development by enhancing turbulent shear and interfacial disturbance. Morphological observations showed that both gasoline-methanol and gasoline-diesel mixing oils presented uniform and transparent diffusion-mixing states without observable stratification or abrupt interface transitions, confirming that turbulent diffusion serves as the dominant mixing mechanism in both systems due to the good miscibility of each liquid pair. Quantitatively, however, the gasoline-methanol mixing oil was consistently shorter than the gasoline-diesel mixing oil under all tested conditions, which can be attributed to the lower viscosity contrast and faster molecular diffusion equilibration between methanol and gasoline.
A significant analogy was identified between the macroscopic diffusion behaviors of gasoline-methanol and gasoline-diesel mixing oils. In both cases, the mixing zone developed symmetrically along the pipeline axis, with concentration profiles exhibiting a gradual transition from the leading liquid to the trailing liquid, in agreement with classical turbulent diffusion models. Increasing the flow velocity shortened the mixing oil length over the same transportation distance for both systems, and the trend remained consistent across all velocity conditions examined. This behavioral analogy suggests that the existing well-established predictive models for gasoline-diesel mixing oil length can be adapted to gasoline-methanol systems by substituting the experimentally determined effective diffusion coefficient for the methanol-gasoline pair into the model framework. The findings of this study provide essential experimental data and theoretical guidance for the engineering design, operational optimization, and risk assessment of methanol transportation in multiproduct refined oil pipelines, thereby supporting the broader application of methanol as a clean alternative fuel within existing pipeline infrastructure.

Key words: methanol, gasoline, batch transportation, mixed oil, pilot test