Research On Three-dimensional Measurement And Volume Characteristics Of Slug Bubble

Gas-liquid slug flow is one of the typical flow patterns of two-phase flow,which commonly occurs in industrial processes such as oil well production,pipeline transportation,and nuclear reactor cooling.Due to its intermittent characteristics,slug flow will cause severe vibration and corrosion of the pipeline system.Therefore,accurate analysis of slug flow characteristics is of great value to pipeline design optimization.In addition,slug flow has the characteristics of enhanced fluid recirculation,which is also of great significance for improving heat and mass transfer efficiency and improving equipment performance.In this work,an optical imaging system is designed based on Laser-induced Fluorescence technology to realize the three-dimensional measurement of slug bubbles.On this basis,the image processing methods,inter-layer interpolation,and Monte Carlo principle are deeply researched to reconstruct the morphology of irregular slug bubble and measure its volume.According to the measurement results,the volume-length model of slug bubble is established.The specific work is as follows.At first,the principle of Laser-induced Fluorescence is adopted to design the optical imaging system,realizing the simultaneous measurement of the cross-sectional shape and horizontal translational velocity of the slug bubble.In order to improve the measurement accuracy of flow parameters,image enhancement,threshold segmentation,image distortion correction methods and image feature matching algorithms are optimized respectively.Moreover,aiming at the characteristics of the bubble cross-sectional image,a spline interpolation method based on pixel position is proposed to achieve inter-layer interpolation,ensuring the smooth transition of the bubble surface morphology.Then the surface rendering algorithm based on the Marching Cube is used to complete the three-dimensional reconstruction,combined with the Monte Carlo principle to measure the volume parameter of the irregular slug bubble.In order to grasp more flow details,the CFD simulation of the three-dimensional flow behavior of slug flow is carried out.Combined with the experimental measurement and simulation,the bubble cross-sectional shape,local void fraction distribution,and local pressure field distribution in slug flow are analyzed in detail.Finally,based on the proposed bubble volume measurement method,a one-dimensional length-volume model of slug bubble is established.The model utilized the easy-to-measure bubble length to predict the slug bubble volume,which is more difficult to measure in the practical application.