成品油管道拖尾油形成机理研究

拖尾油是混油的尾段。在成品油顺序输送过程中不可避免地会产生拖尾油，而拖尾油会污染后行油品。在盲管段主要是由于死油区的前行油品混入主管而形成拖尾油。传统的混油量计算式没有考虑拖尾油的影响，采用雷诺时均法对紊流进行模拟计算，利用CFD对不同的流速及盲管长度的情况进行模拟得到混油相关实验数据，模拟结果表明，盲管中油品替换速度与流速呈指数关系，为使混油量较小，流速最好控制在1.6 m/s内。盲管长度与油品替换时间呈指数关系，为减少混油量，盲管长度应小于5倍主管管径。利用MATLAB对盲管段油品替换时间、盲管长度和流速进行多元非线性拟合，得到盲管段所产生的拖尾油长度，结合混油长度计算的Austin-Palfery式得到混油长度的计算修正公式。对比现场实际数据表明，修正公式计算得到的混油量更加接近实际值。

Study on Formation Mechanism of Trailing Oil in Product Oil Pipeline

Trailing oil is the tail section of contamination in oil pipelines. It is generated in batch transportation, and it has an effect on the quality of oil. In the dead-leg section, the main reasons for the formation of trailing oil contamination is the outflow of the preceding batch that remains in the dead-legs. The traditional calculation formula of oil mixing does not consider the influence of trailing oil. The Reynolds time-averaged method is used to simulate turbulence. To obtain contamination-related experimental data, Computational Fluid Dynamics (CFD) software is used to simulate different flow rates and bypass lengths. The oil replacement rate in a dead-leg is exponentially related to the flow speed and the length of the dead-leg is exponentially related to the replacement time of the oil. To reduce the amount of contamination, the main flow speed should be kept at about 1.6 m/s, and the length of the dead-leg should be less than five times the diameter of the main pipe. The MATLAB software was used to perform multi-nonlinear regression for the oil substitution time, the length of the dead-leg, and the flow speed to calculate the contamination length. A modified equation for calculating the length of the contamination was obtained by combining the Austin-Palfery equation with new factors. Using engineering data, the contamination predicted by the corrected equation is closer to the actual contamination than that predicted by other equations.