Study On Optical Measurement Of Phase Distribution For Bubble Flow And Slug Flow In Small Channels

Gas-liquid two-phase flow in small channels exists widely in the fields of energy,petroleum,chemical industry,etc.Research on process parameter measurement of gas-liquid two-phase flow is key to the safety and efficiency of industrial production and can provide effective data for theoretical research and modeling.However,due to the complex characteristics of the gas-liquid two-phase flow in small channels,conventional parameter measurement techniques still need to be improved.Based on optical measurement technique and principle of geometrical optics,research on phase distribution measurement of bubble flow and slug flow in small channels is carried out.The main work and innovations of this dissertation are as follows:1.An optical measurement system for gas-liquid two-phase flow in small channels is designed and developed.In this system,two laser sheets are used to irradiate the gas-liquid two-phase flow horizontally and vertically.Meanwhile,two high-speed CMOS sensors are used to measure the light intensity distributions generated as the laser sheets pass through the gas-liquid two-phase flow.Based on the light intensity distributions,information of the phase distribution of the two-phase flow can be further obtained.2.A new phase distribution measurement method for bubble flow and slug flow in small channels is proposed.Firstly,an adjustable ellipse with parameters(x,y,a,b)is used to characterize the cross-sectional phase distribution of bubble flow and slug flow,the corresponding light intensity distribution is calculated based on principle of geometrical optics.Then,features of the light intensity distribution are extracted and the relationship between the features and the phase distribution parameters(x,y,a,b)is analyzed.Based on the relationship,the phase distribution model of bubble flow and slug flow in small channels is established.Finally,the least square method is used for model recognition.3.Based on the presented phase distribution measurement model,the bubble profile of gas-liquid two-phase flow is reconstructed.According to the measurement results of light intensity distribution,the phase distributions at different sampling instants are obtained and utilized to reconstruct the profile of bubble.Experimental results indicate that the presented method is effective.4.Based on the phase distribution measurement model,a method of estimating the liquid film thickness of gas-liquid two-phase flow in small channels is proposed.According to the phase distributions measured at different sampling instants,the thickness of the liquid film can be estimated.Experimental results indicate that the proposed method is feasible,and the estimated liquid film thickness is in accordance with existing empirical formulas.