管道顺序输送高差混油研究

Research on contamination caused by elevation difference in batching transportation

成品油管道线路起伏时相邻油品的密度差和粘度差是影响混油形成的重要因素。分析了两者对混油过程的影响 ,推导出了与混油区的物质分布相关的轴向有效分散系数 ,提出了管道顺序输送高差混油模型。湍流时 ,粘度对流速断面形成的影响在油流核心不明显 ,主要是密度差别导致流速断面变化而影响有效分散系数 ,因此 ,可忽略混油区粘度的变化。在此基础上简化模型 ,推导出了高差混油浓度分布的基本方程。通过算例对雷诺数、管长和倾角等影响混油的因素进行了分析。结果表明 ,倾角对混油的影响程度随着输送距离的增长和雷诺数的提高逐渐减小 ,特别是在高于临界雷诺数的高度湍流和长距离输送时 ,倾角对混油的影响程度相当小。

Density and viscosity differences between adjacent miscible products are the important factors affecting the contamination formed in the undulate multi_product pipeline.The effects of dendity and viscosity differences on contamination process were analyzed.The virtual axial dispersion coefficient related with mass distribution in mixing section was determined.A mathematical model of contamination caused by elevation difference in batching transportation was proposed.In turbulent flow,the influence of oil viscosity on formation of flowing velocity profile was not obvious in the core of oil flow.The change of flowing velocity profile resulted from the density difference had some effect on virtual axial dispersion coefficient.So the model was simplified without consideration of the viscosity variation,and an equation for contamination concentration distribution caused by elevation difference was developed.The factors affecting contamination,such as Reynolds number,pipeline length and inclination angle,were analyzed by means of several examples.The computation results showed that the effect of inclination angle on contamination decreased gradually with the increase of pipeline length and Reynolds number.Particularly,the degree of effect became invisible when pipeline was in completely turbulent flow,and Reynolds number was greater than critical Reynolds number while the pipeline was considerably long.