Research On Measurement Method Of Liquid Film And Phase Fraction In Gas-Liquid Swirling Flow

Gas-liquid two-phase flow is a common phenomenon of fluid flow in nature and industrial applications,which is widely used in chemical,metallurgical and aerospace fields.Gas-liquid swirling flow is a special form of gas-liquid two-phase flow.It is a rotational motion,which superimposes both circumferential and radial velocities in the axial direction.This flow pattern has a very important application in the industrial process.In this study,the flow parameters of liquid film and phase fraction in gas-liquid swirling flow are studied,in order to further understand and explore the gas-liquid swirling flow,and to provide new technical means for industrial applications.Firstly,a coaxial capacitance measurement method for gas-liquid swirling flow field is proposed.The principle of the method is given,and the structure of the hydrocyclone and capacitance sensor is designed.In this flow field,the gas phase flows in the center of the pipeline in the form of gas nucleus and the liquid phase flows along the pipe wall in the form of liquid film,which effectively overcomes the influence of flow pattern on the measurement of capacitance sensor.Secondly,the water volume fraction experiment is carried out on the horizontal wet-gas test loop of Tianjin University.Capacitance signal shows that the sensor has a good resolution for water volume fraction.Because the capacitance signal reflects the information of water holdup,a model for predicting the water volume fraction based on the slip ratio of swirling flow is proposed,and the relationship between water volume fraction and water holdup is established.The measurement of the water volume fraction within 10%is realized,with an average absolute error of 0.24%.Thirdly,based on the experimental method of conductivity probe,the liquid film of swirling flow is studied and the distribution of circumferential liquid film of swirling flow under three experimental installation modes is investigated.The non-uniformity parametert_at _m^-1 of circumferential liquid film of horizontal swirling flow is proposed to reflect the non-uniformity of circumferential liquid film distribution.Based on Martinelli parameter X,the model oft_at _m^-1 is established.The average relative error of the model prediction is 3.79%.At the same time,the vertical positive U-type is determined as the optimum installation mode.On this basis,the prediction model of average liquid film thickness of vertical swirling flow is established,and the average liquid film thickness of swirling flow can be predicted.The average relative error is8.26%.Finally,the structure of capacitance sensor is further optimized,and the vertical measurement scheme is proposed.The vertical dynamic experiments of 0-10%low water volume fraction and 10-40%high water volume fraction are carried out,and the measurement of water volume fraction in the range of 0-40%is realized.Normalized capacitance parameter C*is defined to establish the model for measuring water volume fraction.The average absolute errors for predicting water volume fraction under low and high water volume fraction are 0.25%and 1.26%,respectively,and the maximum value of repeatability is 0.76%.