Research On Structure Optimization And Measurement Model Of Near Infrared System Based On Rectangular Differential Pressure Flowmeter

Gas-liquid two-phase flow is widely appeared in field of industrial production.The measurement of flow,phase holdup and other parameters is of great significance for the control and safety of the production process,so the accurate measurement on the related parameters of gas-liquid two-phase flow is particularly significant.This paper combines a differential pressure flowmeter with near-infrared spectroscopy to design a new type of gas-liquid two-phase flow detection device for rectangular pipelines,achieved two-phase non-separation measurement.The main work is as follows:First,a rectangular differential pressure flowmeter is designed.Using CFD fluid simulation software,combined with the basic theory of gas-liquid two-phase flow,three structural parameters affecting the performance of the flowmeter:plate spacing,shrinkage angle and expansion angle is simulated and determined.Secondly,established the gas liquid two phase flow measurement system,pressure acquisition and storage system,near infrared signal acquisition and storage system,and the single-phase experiment is carried out on the vertical installation of gas-liquid two-phase flow detection device.Single-phase water flow ranges from 1m3/h to 11m3/h,and a single-phase water flow calculation model is obtained.The relative error of single-phase water flow is within 0.8%.Finally,based on the single-phase flow experiment,the gas-liquid two-phase flow dynamic experiment was carried out.The liquid flow rate range was 1m3/h~11m3/h,and the gas flow rate range was 0.12m3/h~0.6m3/h.By analyzing the relationship between the four-channel near-infrared signal and the phase holdup ratio,a phase holdup measurement model was established and the liquid phase holdup error was within 3.5%.By comparison,it is found that the homogeneous flow model has a better prediction effect on the point where the liquid flow rate is greater than 2m3/h.Modified the classic model to correct the model total flow measurement error within 4.5%.Establish the relationship of two-phase differential pressure,Fr_g,Fr_l,and combine the phase-containment rate measurement model to obtain the total flow measurement model,in which the total flow relative error of the slug flow is within6.5%,and the total flow relative error of the bubbly flow is Within 1.5%.