Research On Flow Structure And Characteristics Of Downward Liquid Film In Annular Flow Based On Laser-induced Fluorescence

As a type of important gas-liquid two-phase flow characterized by the low liquid flow rate,little power consumption and excellent mass and heat transfer,annular flow has been widely used in the fields of chemical industry,energy,metallurgy,aerospace and so on.It is of great significance to accurately measure its parameters and further study the flow mechanism.Laser-induced fluorescence(LIF)is a non-invasive,high spatial-temporal multiphase flow diagnostic technique.The vertical falling film and the liquid film of gas-liquid annular flow in downward pipe along the axial section of the pipeline are measured based on the LIF technique.Aiming at the vertical falling film and the liquid film of gas-liquid two-phase annular fluid,the spatial-temporal flow structure analysis are carried out at different liquid-phase Reynolds numbers and different gas-liquid apparent velocities respectively.For the circumferential liquid film along the radial section of the pipeline,the visual dual-view sensor is designed,analyzed and optimized in this paper.The sensor increases the effective measurement angle of the liquid film in the circumferential direction.At the same time,the optimized sensor is used to measure the circumferential liquid film.The specific work is as follows:1?Based on the analysis of domestic and abroad measurement of liquid film in annular flow,the LIF technology for non-intrusive and whole field measurement is adopted.The characteristic parameters of vertical falling film under different Reynolds numbers are extracted and compared with the classical research models.Through analyzing in time-frequency domain and the reconstructed liquid-film spatial-temporal structure image,the flow fluctuation and flow mechanism of the liquid film are studied and analyzed.2?Aiming at the gas-liquid two-phase annular flow,the axial liquid film in the vertical downward pipe section is measured and analyzed by LIF at different gas velocities and liquid velocities.The characteristic parameters of the liquid film are extracted and the influence of gas-liquid phase velocities on the disturbance of liquid film is analyzed.The spatial-temporal structure of the liquid film is reconstructed,and the spatial-temporal structure and flow mechanism of the annular flow liquid film are realized.3?Aiming at the circumferential liquid film in the radial section of the pipeline,in order to increase the effective measurement angle,a virtual dual-view visual sensor is designed and optimized.At the same time,the actual circumferential liquid film under different liquid-phase Reynolds numbers is taken by LIF.The sensor device can realize the measurement of the flowing state of the circumferential liquid film in a high spatial-temporal resolution.