Investigation On The Characteristics Of Gas-liquid Two-phase Flow With Low Liquid Holdup In Horizontal/micro Tilting Pipe

In the process of wet natural gas pipeline transportation,with the influence of terrain and other factors along the pipeline,the parameters,such as temperature,pressure,etc in the pipeline will change,resulting in the precipitation of liquid in the pipeline.When the transportation speed of wet natural gas is low,the liquid precipitated from the pipe will deposit in the pipeline,forming liquid accumulation.The liquid accumulation in the pipeline will not only reduce the area of the gas transportation channel to affect the gas transportation efficiency,but also corrode the pipeline,increasing the energy loss in the pipeline,even causing accidents when the pipeline is seriously blocked.The characteristics of gas-liquid two-phase flow in the process of natural gas pipeline flow play vital roles to the design of pipeline size,selection of pressurization equipment,pigging times and prevention of gas hydrate formation.Accurate prediction of critical liquid carrying velocity,pressure drop and liquid holding rate in wet natural gas transportation is of great significance to prevent liquid accumulation in wet natural gas pipeline,design of pipeline and reduce operation cost of enterprises.In this paper,the flow mechanism of the liquid accumulation in the wet natural gaspipeline is studied.For the gas-liquid two-phase stratified flow with a low liquid holdup in the micro inclined pipeline,based on the gas-liquid two-phase flow balance equation and the new gas-liquid interface shape a closed relationship,_a critical liquid carrying velocity prediction model considering droplet entrainment is established.Meanwhile calculation models of friction pressure drop and liquid holdup of low liquid holdup gas-liquid two phase smooth stratified flow and wave stratified flow for considering droplet entrainment are established according to the criterion of flow pattern transition.Combined with the experimental data,the model of this paper is verified and compared with the FLAT interface model,ARS interface model,Double-Circle interface model and MARS interface model.The results show that model of this paper is of higher prediction accuracy and can be used to predict the critical liquid carrying gas velocity,pressure drop and liquid holdup in wet natural gas pipeline.The effects of pipeline inclination,operating pressure,liquid density and natural gas composition on critical liquid carrying velocity and critical liquid holding capacity in micro inclined pipeline are analyzed.At the same time,the effects of pipeline diameter,liquid flow rate,liquid density,gas flow rate,operating pressure and natural gas components on the pressure drop and liquid holdup in the pipeline are analyzed.In this subject research,theoretical bases for the design and efficient operation of wet natural gas pipeline are provided.