Study On The Law Of Gas-liquid Two-phase Flow With Low Liquid Volume And Liquid Carrying In Inclined Pipe

Low liquid volume gas-liquid two-phase flow widely exists in the process of natural gas exploitation and transportation.When transporting gas-liquid two-phase flow in undulating terrain or other complex terrain,it is easy to form liquid accumulation in low-lying areas of the pipeline,reducing the efficiency of natural gas collection and transportation.In addition,the problem of wellbore liquid accumulation is more common during the development of gas wells,which can reduce the production of gas wells and shorten the life of gas wells.Therefore,clarifying the liquid carrying mechanism and liquid accumulation prediction method,and determining the flow pattern of low liquid content gas-liquid two-phase flow in inclined pipes have important theoretical significance for ensuring wellbore production and safe operation of pipe networks,and optimizing production processes.In this paper,the low liquid content gas-liquid two-phase flow in inclined pipes is studied by means of experimental research,theoretical analysis,numerical simulation,and model comparison verification.The main research contents are as follows:(1)A total of 571 sets of experimental studies were conducted on low liquid content gas-liquid two-phase flow in inclined pipes using water and air at 10 pipe angles.Image capture and data acquisition were performed using high-speed cameras and pressure differential sensors.The flow patterns of gas-liquid two-phase flow in inclined pipes were observed to be slug flow,agitated flow,annular flow,and transition flow from agitated to annular flow.The variation rules of liquid holdup and pressure drop with gas liquid flow rate and pipeline inclination angle are analyzed and summarized.Under low liquid volume conditions,pipeline inclination angle has little impact on liquid holdup,but has a significant impact on pressure drop within the range of 0-55 °inclination angle,and its impact mechanism is given.(2)Based on experimental data,a pressure drop calculation model for low liquid content gas-liquid two-phase flow in inclined tubes was established by fitting and modifying the liquid holdup inclination correction coefficient based on the Beggs Brill model.Using experimental data to compare and verify the model and existing models,it is proved that the model has high accuracy and can be used to predict the pressure drop of low liquid volume gas-liquid two-phase flow in inclined pipes.(3)A liquid carrying experiment was conducted,and the results showed that the inclined section was the most prone position for liquid accumulation,with the most prone angle for liquid accumulation at 55 °.At the same time,numerical simulation was used to study the gas-liquid two-phase flow state under different inclination angles and gas flow rates.Compared to high-speed camera images,the flow details of the liquid film inversion during the critical liquid carrying state were more intuitively obtained,and the effects of pipeline inclination angles and gas flow rates on the cross-sectional liquid holdup were analyzed,verifying that the liquid holdup fluctuation curve can be used to distinguish the flow pattern.(4)Based on the circumferential model,considering the uneven distribution of the thickness of the liquid film in an inclined tube,and considering the changes in gas and liquid quantities,an expression for the average thickness of the liquid film was derived,and a new model was developed to predict the critical gas flow rate.The comparison of the new model with laboratory and field data shows that it has better performance and applicability than other models used in the past to predict liquid accumulation,providing a basic theoretical basis for predicting the critical liquid carrying flow rate in inclined pipes.The research content of this article provides a theoretical basis for the study of low liquid content gas-liquid two-phase flow in inclined pipes,and has good reference value for engineering applications.