Being aimed at the problem of contaminated oil in batch transportation of the same gasoline and diesel on different density condition during product oil flowing through the downhill and uphill, with the help of VOF model, the numerical calculation of threedimensional flow model was established. The influence of contaminated oil from different sequence，density，pipe range on boundary layer region was researched on the uphill and downhill road. The results showed that for uphill pipeline the length of the mixed oil of forward diesel was longer than forward gasoline，and the mixed oil volume of forward diesel was greater than forward gasoline. For downhill pipeline the length of the mixed oil of forward gasoline was longer than forward diesel and the mixed oil volume was greater than forward diesel. During forward the same gasoline and trailing diesel for different density diesel, the smaller density could help reduce mixed oil volume.

In batch transportation of finished oil products, mixed oil would be produced by adjacent batch oil. The cases of 30°, 45°,60° or 90° for the joint line of the variable diameter part and the straight pipe of the variable diameter pipe were calculated by the CFD software. The conclusion show the relationship and the change law between the angle of the joint of the variable diameter part and the length were researched. The results show that with the angle increased, the mixed oil segment length decreased in the sudden expansion pipe and the opposite conclusion in the reducer, which was coincided with engineering basic phenomenon.

In regions of complex terrain, refined oil will inevitably pass after elevation, shutdown, such as downhill different path. The pipe inclination angle and shutdown time of downhill pipeline blending have a great influence on mixed oil characteristics. Using CFD multiphase flow model and studying three-dimensional inclined pipe, on the shutdown time, angle and sequence transportation on mixed oil characteristics were numerically simulated respectively. The results of the study show that before shutdown while the forward gasoline and backward diesel, the dip angle is bigger, the mixed oil quantity is less; the inclination angle is smaller, it is more prone to mixed oil. When the forward diesel and backward gas ,contaminated tail is longer and the inclination angle is bigger, the mixed oil quantity is bigger while the inclination angle is smaller, the mixed oil quantity is less but there is less effect on the mixed oil. The inclination angle has greater influence on the former than the latter.After shutdown, the longer the time of shutdown is, the more the mixed oil is with the equal angle. With the same time, the bigger the angle is, the greater the mixed oil. While the forward diesel and backward gasoline, with the shutdown time prolonging the mixed oil quantity is more and more uniform. When the inclination angle and the angle of pipeline is the same, shutdown time and angle has greater influence on the condition of the forward gasoline and the backward diesel.