Study On The Gas & Liquid Multiphase Transportation Pipeline Pressure Drop Model

With the development of the oil industry,as well as the rising demand for oil,the proportion of oil imports is constantly increasing.Under this circumstance,people pay more and more attention to costs of transportation,making long-distance oil and gas pipeline been widely used due to its huge advantage in terms of its economy and security.At present,The flow type of long transport pipeline is mostly gas-liquid two-phase flow.Studies of gas-liquid two-phase flow are mostly about horizontal two-phase flow or vertical two-phase flow,but the problem is in the actual laying process,gas-liquid mixed pipeline often wear across some obstacles,which brings an angle of tilt.Because of the complexity of gas-liquid two-phase flow,the application of horizontal two-phase flow model or vertical two-phase flow model brings a very large deviation and low prediction accuracy.Also,the existing pressure drop calculation model can hardly be widely used,so study regarding gas-liquid two-phase flow requires instant efforts.In this paper,the study on the low-angle atmospheric-liquid ratio two-phase flow is the main point.The pressure drop around the gas-liquid two-phase flow is discussed from the following aspects:The research progress of gas-liquid two-phase flow pattern and pressure drop model at home and abroad were summarized.Based on the study,it is found that research on flow pattern of gas-liquid two-phase flow in inclined pipe was relatively few in the past,and experience-based flow pattern method was widely used in most studies;in addition,the application of pressure drop model,in current situation,has limitations;finally,the three kinds of treatment methods and four basic models of pressure drop are summarized.Design and conduct experiment on small angle atmospheric / liquid ratio two-phase flow.The experience was conducted in a plexiglass tube with an inner diameter of DN60.During the experiment,the flow rate of the two-phase gas-liquid flow,average pressure,pipe pressure drop,holding rate and temperature and other basic parameters were measured.Meanwhile,experimental flow chart was drawn,the influence on flow pattern exerted by pipe inclination was summarized,and the flow pattern with the pipe inclination of 15° was also analyzed by utilizing the flow pattern pictures shot during the experiment with the help of the high speed camera system.The conclusion that the flow pattern and the transformation of flow pattern would have a direct influence on the liquid holding rate and pressure drop was obtained.Therefore,the pressure drop model based on flow pattern should be given priority when calculating the pressure drop of gas-liquid two-phase flow.Based on the experiment,the formation mechanism of the annular flow was analyzed,the mechanism model of the annular flow formation was established,and the limit equation of the flow pattern was obtained.Two methods to calculate the liquid holding rate and three ways to calculate pressure drop based on flow pattern were selected to predict the theoretical liquid holdup and pressure drop under experimental conditions.Through the error analysis,the coefficients in the Beggs-Brill method with the least error were chosen to correct the angle,and the error was obviously reduced after the correction.And then the formula for calculating the pressure drop of the two-phase flow was obtained.In this paper,the influence of the inclination angle on the pressure drop was analyzed theoretically.Based on this study,the empirical formula was obtained by optimizing the pressure drop model.The empirical formula can be applied to the experimental conditions and can be used to predict low pressure atmospheric / liquid ratio.