For the study of variable diameter tube affects the quantity of sequential oil transportation of the refined oil, applying multiphase flow model, the 90# gasoline and 0# diesel oil as the object of alternate transportations, according to different variable diameter pipeline structure form and different tapered Angle on the oil transportation.The results show that the growth rate of the length of the mixing section decreases obviously and the length of the mixing section decreases for a short time when the mixing oil enters the sudden expansion pipe, then the length of the mixed oil section growth accelerated obviously, but inferior to the level before variable diameter and with the increase of taper Angle, the different length were mixed with different degrees of decreased; after the mixed oil section flows into reducing pipe, the length of the mixed oil section growth obviously larger, and appeared the trend of decrease, but still higher than before the variable diameter, and with the increase of tapered tube taper Angle, the length of the mixed oil section all have varying degrees of increase.

In order to study the problem of distribution of mixed oil in T-shape pipeline of refined oil products. And the control equation of the sequential transport mixed oil is established by using multiphase flow model, 90 ^# gasoline and 0 ^# diesel are used as the alternate transportation objects. The process of downloading the mixed oil formed by gasoline and diesel under different conveying sequences through the branch pipe is numerically calculated, and the distribution of mixed oil quantity is obtained. The influence of the mixed oil in the main line on the mixed oil section under different conveying sequence is analyzed. The results show that the mixed oil in the main pipeline can be shortened by the appropriate amount of oil in the station provided along the line, which can significantly shorten the length of the mixed oil section and reduce the download pressure on the mixed oil section of the pipeline at the end station.