| Multiphase flow is ubiquitous around us,widely exists in industrial applications,and has great economic significance.Multiphase mixed technology of transportation is of great significance to the development of onshore and offshore oil and gas fields.In fluid transportation the elbow is an important pipe part.It changes the velocity and the direction of fluid.At the same time,the elbow would suffer the huge pressure and imp act.This paper simulates the oil-gas-water multiphase flow in the combined pipe with double elbow and risers,The reverse z-type pipe and the n-type pipe combined with the above two pipes by CFD,which analyzed the variation of wall pressure under different angle of elbow,length of risers,velocity of inlet and Crude oil viscosity,gas volume fraction's flow pattern and distribution of velocity of the fluent in Z-shaped pipes.The results of the experiment shows that with the increase of the angle of the bend,the pressure which come from the fluid on the outside diameter wall of the elbow decrease,and the area of action surface increases.And if we increase the length of the riser,the wall pressure of the elbow is decrease.Moreover it is easy to form a slug flow in pipe which is difficule to be discharged.The increase of fluid inlet velocity will increase the external wall pressure of the curved pipe significantly to a certain extent,and the increase of fluid velocity at a large speed will not change the external wall pressure significantly.In the inverted z-type pipe,the pressure distribution is basically the same as that in the z-type pipe,but under the action of gravity,themaximum velocity appears at the outside diameter of the second bend.With the increase of crude oil viscosity,the oil phase gradually developed from oil droplets to larger oil masses.With the increase of gas volume fraction,the fluid gradually developed from small bubbles to large bubbles,and the flow pattern also developed towards the flow of bubbles to slug flow. |
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