Measurement Of Gas Phase Characteristics In Bubbly Oil-Gas-Water Flows Using Optical Fiber Sensor Array

Oil-gas-water three-phase flows are frequently encountered in petroleum exploitation and transportation industrial processes.The flow structures are more complicated due to significant differences in physical property and mutual interactions among phases,which makes it a great challenge to measure local flow parameters.Bubbly flow is a fundamental structure in three-phase flows and a comprehensive knowledge on local gas phase characteristics is of significant importance to design and optimize the structure of sensor as well as to develop oil-gas-water three-phase flow models.Considering the unique advantage of optical probe in high sensitivity to detect gas,two schemes:traversing bi-optical fiber probe and distributed probe array,are proposed to measure local gas flow characteristics comprehensively in this paper.Zemax software is used to optimize geometric construction of optical probe and experiments are carried out to investigate radial distribution of gas concentration,velocity along with chord length distribution of bubbly flows in a vertical upward pipe with small inner diameter.Moreover,nonlinear dynamic characteristics analysis is conducted based on signals collected by high-resolution conductance sensor.Several innovated results of this study are stated as follows:1.When U_sgg is low,the peak value of gas volume fraction appears near the pipe wall,and the peak shift to the center with U_sll increasing.When U_sgg is high,the maximum of gas volume fraction is always at the center and the minimum is always at the wall.The profile of gas volume fraction presents regular parabola-shape.When f_o is increasing,gas volume fraction at the center increases slightly and decreases at the wall accordingly,but the shape of profile remains unchanged.2.Local gas velocity is the largest at the center,and decrease with the increasing distance from the central part.The velocity also increases with U_sgg and U_sll increasing.Bubbles movement is obstructed and the velocity at every position decreases with f_o increasing.3.Bubble size at all positions in radial direction increases with rising U_sgg and decreasing U_sl.The distribution of bubble size will be more homogeneous when U_sll is high.Besides,increasing f_o will cause bubble coalescence and the bubble size will increase as well.4.Three-dimensional imaging of gas concentration is performed to reveal the spatial distribution regularities intuitively based on signals derived from distributed optical fiber probe array sensor.Results show that distributions of imaging agree well with the results derived from traversing bi-optical fiber probes and they are sensitive to the variations of nonlinear dynamic characteristics of flow system.