Study On Measurement Method Of Bubble Flow Parameters Based On High-speed Camera Method

Gas-liquid two-phase flow widely exists in nature,process industry,biomedicine and other fields.The measurement of its flow parameters is of great significance for the application of complex hydrodynamic characteristics analysis,flow process control system design,process production state prediction,and abnormal state diagnosis and so on.However,due to the complex interaction between gas-liquid two-phase flow,complex and changeable flow patterns,and the highly nonlinear flow process,there are many difficulties in the accurate detection of gas-liquid two-phase flow parameters,mainly manifested in the low measurement accuracy and the influence of specific flow conditions.Based on this,a "bubble flow parameter measurement method based on high-speed camera method" is proposed to measure the geometric parameters of uniform and non-uniform bubbles in vertical pipes.The main work is as follows.(1)The dynamic experiment platform of gas-liquid two-phase flow is built,and the dynamic experiment of gas-liquid two-phase flow in 50 mm inner diameter vertical pipeline is designed.Under different flow conditions,a large number of transient morphological images of gas-liquid two-phase flow were collected by high-speed camera,and the evolution law and flow characteristics of gas-liquid two-phase flow were summarized.On this basis,the flow pattern of vertical gas-liquid two-phase flow at low velocity is defined,and the flow pattern diagram is summarized.The boundary of gas-liquid two-phase flow transition from slug to bubble flow is determined experimentally,and compared with the existing theoretical flow pattern transition boundary,the evolution law of gas-liquid two-phase flow is clarified.(2)A method of "parameter measurement of non-uniform rising bubbles based on image processing technology" is proposed.Through the contour detection and image positioning of the high-speed image of non-uniform bubble flow,the parameters such as area,perimeter and rising speed of non-uniform rising bubble are measured.The relationship between nonuniform rising bubble parameters and flow conditions is studied and summarized.The results show that when the gas-liquid mixing velocity is constant,the rising velocity of the bubble is negatively correlated with the equivalent area of the bubble;With the change of gas-liquid mixing velocity,the average area of non-uniform bubbles is negatively correlated with the mixing velocity and the rising velocity of bubbles,and the rising velocity of bubbles is positively correlated with the mixing velocity.(3)A "measurement method of uniform bubble flow parameters based on improved Res Net-UNet network" is proposed to measure the geometric parameters of uniform bubble flow.The improved Res Net-UNet network realizes the segmentation of bubble and liquid environment by combining UNet network and Res Net residual network and adding a new input normalization layer.In addition,this paper adopts the methods of "concave point matching algorithm based on k-cosine curvature calculation" and "least square ellipse fitting" to solve the error caused by bubble adhesion in geometric parameter measurement.The measured parameters such as bubble flow area and perimeter are jointly analyzed with the measurement index of fluid complexity.The results show that with the increase of mixing velocity,the perimeter and area of uniform bubbles tend to decrease,and their morphology gradually has irregular distortion,bubbles gradually change into regular spherical bubbles,and the complexity of gas-liquid two-phase flow system also increases gradually.