Measurement Of Gas Phase Characteristics In Gas-liquid Two-phase Flows Using Optical Fiber And Conductance Sensors

Gas-liquid two-phase flows are widely existed in petrochemical,nuclear industry,power engineering and other fields.The flow behaviors are of high irregularity,randomness and instability due to complex interaction in gas-liquid two-phase flows,which lead to a great challenge to measure the flow parameters.A comprehensive understanding of local flow characteristics of gas-liquid two-phase flows.is of great significance to monitor the production process in real time and optimize flowrate sensor.A combined measurement system of optical sensor and conductance sensor is proposed to measure local flow parameters of gas-liquid two-phase flows in vertical upward small pipe.We optimize the structure of conductance sensor by ANSYS.We performed experiment of gas-liquid two-phase flows to investigate the radial distribution of concentration,velocity along with chord length distribution of three flow patterns(slug flow,churn flow,bubble flow).Then the drift flux model is developed based on the measurement results of quick closing valves and arc shape conductance sensor.The innovated results of this study are stated as follows:1.The radial distribution of local gas holdup and velocity in slug and bubble flows present in parabolic shape while the distribution in churn flow under low turbulence increase and then decrease from the wall to the center of the pipe.The distribution is gradually transformed to parabolic shape with increasing turbulence of the fluid.Large gas blocks in churn flow do not appear in the center of the pipe and the chord length reaches the maximum on both sides of pipe centerline.The chord length of bubble flow gradually increases from pipe wall to the center.2.The temporal evolution characteristics of the flow structure in gas-liquid two-phase flows in different flow patterns are analyzed by Local Detrended Cross-Correlation Analysis(LDCCA).The flow structure evolution of slug flow is more obvious when the gas slug and liquid slug alternate while the evolution in churn flow is more obvious near the pipe center.As for bubble flow,the flow structure evolves more easily in the center of pipe.The above conclusions are in good agreement with the results of multi-scale detrended cross-correlation analysis.3.The gas holdup of different flow conditions are obtained by quick closing valves to correct the holdup which measured with arc shape conductance sensor.According to the corrected gas holdup,we established the drift model of vertical upward gas-liquid two-phase flows and predict the holdup of slug flow,churn flow and bubble flow.Absolute average relative error is less than 10%,which shows good gas holdup prediction effect.