Study On Flow Characteristics Of Two-phase Flow In Sudden Contraction Tube

In the actual production of oil and gas fields,gas and water are usually mixed in oil products in gathering and transportation system and long distance pipeline network,so two-phase and multi-phase flow are common in pipeline transportation.As a common pipe connection mode,it is very important to study the change of two-phase flow characteristics in the sudden contraction pipe.Based on the knowledge of fluid mechanics theory,the flow pattern of oil-water two-phase flow and gas-liquid two-phase flow through the sudden contraction pipe is numerically simulated by FLUENT software,the effects of these factors on flow pattern and local drag coefficient were investigated.Based on the pressure nephogram,phase distribution nephogram,streamline diagram and velocity vector diagram,we find the following change rule: the two-phase fluid will form a vortex on the pipe wall near the sudden contraction section before and after flowing through the sudden contraction section;The flow direction of the upper and lower eddies is different,but the eddies are maintained by exchanging momentum with the central main flow The influence length of the velocity core area in the small diameter pipe increases with the decrease of the inlet velocity and the increase of the sudden contraction ratio.For gas-liquid two-phase flow,the size and position of the vortex change with the flow pattern,and the influence of the velocity core area in the small diameter pipe increases with the increase of the length inlet velocity,the liquid viscosity and the sudden contraction ratio.When the difference between oil viscosity and water is too large,the larger the Oscillation amplitude of the pressure curve and the higher the water cut,the faster the pressure drops When there is little difference between the viscosity of oil and water,the pressure drop in the large and small sections is independent of the water cut,and the pressure drop in the sudden contraction section decreases with the decrease of the water cut,the more the pressure rises,the less obvious.The coefficient of local resistance decreases with the increase of sudden contraction ratio,independent of water content,oil viscosity and inlet velocity.In this paper,the two-phase flow in the pipe sudden contraction section is simulated under the conditions of different two-phase inlet flow velocity,oil viscosity,water content(liquid holdup of gas-liquid two-phase flow)and pipe sudden contraction ratio.The flow characteristics of different kinds of two-phase flow in the pipe sudden contraction section are shown by cloud chart,and the influence rules of the above factors on the flow characteristics of two-phase flow in the pipe sudden contraction are summarized.The research results are helpful for understanding Perfect the two-phase flow calculation method of the pipe with sudden contraction,and provide the theoretical basis for optimizing the structure design of the two-phase flow pipe.