Study On The Formation Mechanism Of Trailing Oil In Product Oil Pipeline

During the process of sequential transportation of oil products,there will be contaminated oil which is inevitable.This mixed oil will reduce the quality of oil products and bring about great losses of economic.At present,there are lots of studies about the contaminated oil,but the research on the trailing oil formed by the adhesion to the pipe wall and other station structures is very few,and the understanding is not profound enough.Those will lead to a large deviation in the field of actual contamination calculation and cutting process of mixed oil.Therefore,it is very important to study the formation of trailing oil in sequential transportation process,which has great guiding function for engineering practice.The formation mechanism of trailing oil in product oil pipeline is analyzed in this paper.It is found that there will be more trailing oil in dead pipe section,inclined pipe section and fluctuating section.The mainly reason of forming trailing oil in the dead pipe is that the leading oil flows into the main pipe.The mainly reason of the formation of the trailing oil in the inclined pipe section and the undulating section is that the leading oil is washed by the rear oil from the wall of pipe These trailing oil can't be ignored,and will have great impact on the quality of oil products,and sometimes,their length can reach at 40%of the total length.On the basis of understanding the formation mechanism of the trailing oil,we used Fluent software,and determined the rational wall function and boundary conditions on the basis of the basic theory of fluid mechanics,the theory of turbulent diffusion and the actual data.The process of oil contamination is simulated by using the model of VOF multiphase flow.The influence of velocity,sequence,diameter and length of dead pipe on the formation of trailing oil,the relationship between the speed of oil replacement in the dead pipe and the length of the trailing oil in the pipe was studied.Through these studies,we learned the effect of dead pipe on the trailing oil,and the optimum velocity and the length of the dead pipe The law of producing less oil in the inclined pipe section is found,and the general understanding of the formation law of the undulating trailing oil is broken.The theoretical formula of the length of contamination oil is corrected,and the effect of the trailing oil of the dead pipe section,the inclined pipe section and the undulating pipe section on the length of contamination oil is considered.This paper also simulates the contamination process during the shutdown of the inclined pipeline,and breaks the general understanding of the law of contamination in the undulating section,and determines the best place of the contaminated oil when the undulating section is stopped.The results of this paper have laid a certain foundation for the theoretical study of trailing oil,and the conclusions of the simulation results have a certain guiding significance for reducing the formation of trailing oil,calculating the length of contamination oil and cutting the mixed oil section in the actual production process.