| Residual water brought by water-replacing-oil operation and diesel oil refining will deposit in the low-lying area of the pipeline in the transportation due to the difference of oil-water density and the fluctuation of pipeline topography.If the velocity of following oil reaches certain value,the water can be carried to the upward inclined section and oil-carrying-water two-phase flow comes into being.Under this situation,the flow pattern of oil-water two-phase flow has significant impact on the pressure drop and critical oil-carrying-water condition.Most of the subjects of present study is situation that oil and water flow together at an initial velocity in a pipe with small diameter to become oil-water two-phase flow later rather than the change rule of the flow pattern of oil-water two-phase flow in the upward inclined section of pipe with big diameter.Therefore,the study on the change of flow pattern of oil-carrying-water two-phase flow in upward inclined pipe is launched in this paper.The flow pattern of diesel-water two-phase flow in upward inclined pipe has been studied by literature research,experiment in flow loop,numerical simulation and theoretical model dedction.Flow pattern maps under experimental and simulation condition has been built.Flow pattern discrimination model of oil-water two-phase flow in upward section has been deducted and fitted,based on which flow pattern of oil-water two-phase flow in upward section of pipe can be decided directly.A series of experiments of oil-carrying-water two-phase flow under several diameters(80 mm?100 mm),inclined angles(10°?45°)and superficial velocities of oil(the flow velocity rises from 0.168 m/s until the water can be carried out of the pipe)were launched using experimental flow loop.The distribution of oil and water in upward inclined section was observed and operation condition parameters and corresponding flow patterns were obtained.Based on experimental condition,ICEM software was used to establish geometric models with different inclination angles and diameters.Based on grid independence study,the grid generation scheme is made.3D Fluent numerical simulation under different diameters and inclined angles were launched according to the principle of dichotomy and the single variable controlling.The numerical simulation methods are proved to be right by experiment results.Flow pattern map within the diameter range of experiment and simulation condition was obtained and the impact of operation data on flow pattern of oil-water two-phase flow in upward inclined section was analyzed.Based on the results of the experiment with 100 mm diameter and the simulaiton with 200 mm diameter,a dimensionless number reflecting force balance has been deducted and flow pattern discrimination model of oil-water two-phase flow in upward section is fitted.The flow pattern discrimination model is verified and corrected with the data of experiment with 80 mm diameter.The result of experiments and simulation indicates:under the above experiment condition,major flow patterns in the pipe are stratified-wavy flow,stratified-wavy flow with water droplets and dispersion of water in oil.The dispersion degree of water phase in the upward inclined section increases from the flow pattern stratified-wavy flow,stratified-wavy flow with water droplets and dispersion water in oil.With the increase of diameter,the upward incliend angle at which the flow pattern whose dispersion degree of water phase is relatively lower will change into a higher one decreases.With the same diameter,the velocity at which the flow pattern transfer occurs decreases with the increase of the inclination angle.At the same inclination angle,the increase of pipeline diameter contributes to the increase of the lowest superficial velocity of oil phase at which the flow pattern whose dispersion degree of water phase is lower changes into the higher one increases with the increase of diameter.According to the flow pattern maps and flow pattern discrimination model of oil-water two-phase flow in upward section,the flow pattern in this section can be predicted with operation data including pipeline diameter,upward inclined angle and superficial velocity and physical parameters of oil and water. |
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