Study On Calculation Method Of Pressure Drop And Liquid Holdup Of Low Liquid Loading Gas-Liquid Two-Phase Annular Flow

Low liquid loading gas-liquid two-phase annular flow is a common flow form in onshore and offshore natural gas gathering and transportation pipeline,as the exploration and development of oil moves to more remote places,the transportation pipelines are getting longer and longer,only calculate pressure gradient and liquid holdup in the pipelines accurately can we ensure the safety and the normal operation of the pipeline.In recent decades,great progress has been made in the study of gas-liquid two-phase flow at home and abroad.However,there are few studies on the low liquid loading gas-liquid two-phase flow.Therefore,in this paper,theoretical analysis and numerical simulation are combined to study the low liquid loading gas-liquid two-phase annular flow in the following aspects.Firstly,the PSD and PDF statistical characteristics of the three flow patterns were obtained through the statistical analysis of the pressure/differential signals of stratified flow?annular flow and slug flow,which provided a basis for the identification of flow patterns.Secondly,for the low liquid loading gas-liquid two-phase annular flow,the calculation models of pressure drop?liquid holdup and entrainment rate of annular flow proposed by Xiao(1990)are improved,and a calculation model of pressure drop and liquid holdup considering entrainment of droplets is established.Based on MyEclipse 10,the calculation process of the improved model and Xiao's original model in this paper was programmed.By comparing the calculation results of the two models with the relevant experimental data,it was concluded that the improved model in this paper has higher calculation accuracy degree and has better effect.Finally,Fluent software was used to establish a physical model for the annular flow in horizontal pipe.Through numerical simulation of each condition,the influences of superficial velocity of gas-liquid phase?pipe diameter? gas-liquid interface tension and other factors on the pressure drop and liquid holdup of the gas-liquid two-phase annular flow were obtained.