| Gas-liquid two-phase slug flow is currently widely used in offshore oil exploration,multi-phase pipeline transportation and chemical industry,and the intermittent characteristics of the plug flow in the vertical pipe will cause intermittent fluid stress impact on the multi-phase mixture pipeline.When the fluctuations are severe enough,it may even cause downtime or damage to the downstream conveying equipment.Therefore,the study of the characteristics and occurrence of the slug flow is important for suppressing or eliminating the slug flow.The microbubble fluid has the characteristics of being difficult to aggregate and slow to move,which will affect the back-mixing flow of the slug flow in the boundary layer during the movement,and thus have a certain influence on the motion characteristics of the slug flow.Due to the intermittent characteristics and relatively complex phase distribution characteristics of gas-liquid two-phase flow,a multi-phase flow online measurement system for vertical pipe is proposed to characterize the slug flow in this thesis.The slug flow experiment was carried out on a slug flow experimental platform with an inner diameter of 50 mm.The main research contents and conclusions of this paper are as follows:A gas-liquid two-phase flow multi-parameter online measurement system is presented.The system combines electrical resistance tomography and high-speed camera with traditional pressure method.It is capable of measuring macroscopic pressure and gas velocity and visualizing slug flow and reconstructing cross-sectional gas-liquid distribution.Experimental study of the slug flow was carried out under different working conditions on the slug flow experimental platform with an inner diameter of 50 mm.By using statistical and nonlinear methods,the variation of the average gas content,liquid gas content,pressure fluctuation and slug generation period of the slug unit are analyzed.Results show that the gas content and pressure fluctuation of severe slug flow have a single peak distribution,which can be used as a reference for flow pattern determination.The fluctuation of gas content in the slug flow shows a large diversity,illustrating the diversified probability distribution from a single peak to many peaks.And the pressure fluctuations show the probability distribution law dominated by the single peak in the high-pressure region.In order to understand the fluid properties of microbubbles,the adsorption characteristics,occurrence characteristics and stability of the microbubbles generated by the microbubble generating pump in the two-phase flow are studied.From the microscopic characteristics of microbubble wall adsorption,microbubbles have less aggregation and characteristics.The result also shows that the change of the outlet velocity of the microbubble generating pump will reduce the production concentration of microbubbles.However,under a certain liquid velocity range,a significant number of microbubbles in liquid are generated stably.Experiments are performed to study the effects of microbubble into the slug flow.Through experimental research,an optimal suppression scheme for slug flow is found to introduce the microbubble fluid into the bottom of the vertical tube.The result shows that under low gas-liquid ratio conditions,the microbubbles passing through the vertical tube will change the flow characteristics of the slug,mainly by enhancing the disturbance of the boundary layer to suppress the movement of the slug unit,thereby suppressing the slug flow.When the gas-liquid ratios are 1.2,1.4 and 1.8,the suppression effect of microbubbles is mostly significant. |
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