Numerical Simulation Of Leak And Diffusion By Small Apertures On Buried Refinery Oil Pipelines

ABSTRACT:Pipeline transportation has the characteristics of low cost, less influence from the outside, low loss and convenient operation and management, so it is the main way of refinery oil transportation. The total mileage of refinery oil pipeline network in China is more than15000km at present. However, the accidents of refinery oil leakage and explosion were frequent at home and abroad due to welding defects (pores, slag, cracks etc.) of the pipeline, corrosion perforation, external injury, construction damage, punch robs the oil etc. Hence once the refinery oil pipeline leaks, it will not only cause great economic loss and affect the public safety and the environment, but also cause other serious accidents such as fire or explosion. Therefore, studies on the leakage and diffusion process of refinery oil pipeline have great significant to predict the spread of refinery oil, develop the emergency rescue scheme and reduce accident loss.The study chose Lan-Cheng-Yu refinery oil pipeline as the object, and established a two-dimensional model of leakage and diffusion of buried refinery oil pipelines. By using the VOF multi-phase flow model, the CFD porous media model and the Realizable k-epsilon model, the computational fluid dynamics method was adopted to simulate its process of leakage and diffusion of diesel oil in the soil. Fistly, the reliability of the model was verified by comparing between the experimental data and the simulation results. Secondly, five factors (such as:the diameter of aperture, the location of aperture, the soil porosity, the soil saturation and the soil temperature) were studied in a detail. Moreover, the influence of these five factors in the process of diffusion was analyzed.In the same condition of other factors, four processes of leakage and diffusion were simulated where the leakage aperture diameter was equal to3mm,10mm.30mm and100mm respectively. The results showed that, the aperture diameter was the main factor to affect the oil volume fraction distribution and the diesel oil’s diffusion velocity. With the increase of the aperture diameter, the range of volume fraction distribution of the diesel and the average speed of the leakage and diffusion of the diesel increased. The aperture diameter had little effect on the water ring out of diesel oil front.In the same condition of other factors, three processes of leakage and diffusion were simulated where the location of aperture was on the right side, right above and right below of the pipeline respectively. The results showed that, the location of aperture was the main factor to affect the shape of oil volume fraction distribution and soil saturation contour. When the location of aperture is on the right side, the diffusion velocity of the diesel oil in the horizontal direction was the maxmum and the diffusion velocity of diesel in the vertical direction was the minimum.In the same condition of other factors, four processes of leakage and diffusion were simulated where the soil porosity was equal to0.3,0.45,0.6and0.75respectively. The results showed that, with the soil porosity increasing, the range of volume fraction distribution of the diesel and the average speed of the leakage and diffusion of the diesel decreased. The soil porosity had little effect on the soil saturation contour.In the same condition of other factors, four processes of leakage and diffusion were simulated where the soil saturation was equal to0.1,0.3,0.6and linear distribution respectively. The results showed that, with the soil saturation decreasing, the range of volume fraction distribution of the diesel and the average speed of the leakage and diffusion of the diesel in the horizontal direction decreased, but the average speed of the leakage and diffusion of the diesel in the vertical direction increased.In the same condition of other factors, four processes of leakage and diffusion were simulated where the average soil temperature was in one of the four seasons (etc:spring, summer, autumn and winter) respectively. The results showed that, with the soil temperature increasing, the range of volume fraction distribution of the diesel and the average speed of the leakage and diffusion of the diesel in the horizontal and vertical direction increased. The soil temperature had little effect on the soil saturation contour.Finally, on the basis of the leakage accident of Lan-Cheng-Yu refinery oil pipeline, the diffusion range of the diesel oil within9minutes was analysed by buliding a model of leakage and diffusion of the pipeline. Then the emergency response was analysed based on the result.The leakage and diffusion model established and the calculation method used in this paper is general, which can be used to simulate the leakage and diffusion of refinery oil pipeline under different regions and conditions. At the same time, the results of this study have important significance for setting up a leakage accident emergency plan and environment control.