Research And Development Of Wire Mesh Sensor And Imaging Measurement Of Two-Phase Flow In Vertical Pipe

Regardless of the transportation of oil and gas on land or the exploration and development of oil and gas in deep water,the flow in the pipeline is usually gas-liquid mixture.Compared with the single-phase flow,the two-phase flow has strong volatility and randomness.The study of the flow properties of multiphase flow is the key to ensure the stability of production and transportation.Wire mesh sensor is a kind of measurement method between local flow parameter measurement and tomography,which can measure two phase flow parameters such as bubble size distribution,phase velocity,interface area and density,flow pattern and so on.Compared with the traditional multiphase flow imaging method,the screen sensor has higher spatial and temporal resolution,and the image reconstruction algorithm is more intuitive and simpler.At present,the screen sensor is widely used in foreign countries,and has been commercialized,but the price is very expensive,the domestic research on the screen sensor is less,the screen sensor measurement technology of autonomy in the field of multiphase flow detection has a broad prospect of development.This paper independently designed and developed a low-cost screen sensor multiphase measuring device for multiphase flow theory research is of great significance.In this paper,a 16×16 conductivity wire mesh sensor is designed to measure the local conductivity of the fluid at the intersection point of the gas-liquid two-phase flow in 50 mm vertical pipes.The data acquisition system consists of excitation module,multi-channel switching module,signal conditioning module and multi-channel data acquisition module.The production of wire mesh sensor includes hardware and software.In the hardware part,the circuit schematic diagram,PCB and signal board were designed in turn.In cooperation with PCI-6229 and PCI-1714 UL,the analog switch chip ADG1434,high-speed buffer LMH6560 MA and OPA656 U are respectively used to realize the function modules such as excitation generation,data acquisition and data transmission,and each module was tested by oscilloscope.The software part realizes the functions of data receiving,data storage and image reconstruction and other functions in turn.The final system can capture images at a speed of up to 15,625 frames per second with a spatial resolution of 3mm.By changing the gas-liquid flow rate,the vertical gas-liquid two-phase flow measurement experiments of bubble flow,slug flow,churn flow and annular flow are carried out.It shows that the imaging measurement system designed by the wire mesh sensor in this paper can identify and measure the gas-liquid two-phase flow at different flow rates stably and effectively.The average liquid holdup of the cross section decreases with the increase of the apparent velocity of the gas phase and increases with the increase of the apparent velocity of the liquid phase.At high apparent gas velocity,the WMS is more sensitive to the amplitude of gas phase signal,and the relationship between the average liquid holdup of section and the apparent liquid velocity is small.The dominant factor is the apparent gas velocity.The accuracy of WMS measurement of phase holdup depends on the apparent flow velocity,the flow state,and the spatial resolution of WMS structure.On the basis of the characteristics of gas-liquid two-phase slug flow and churn flow in vertical riser pipe,the average gas holdup,phase distribution of cross-section,side pseudoview and PDF curves of slug flow and churn flow are studied by WMS in the vertical riser pipe.According to the cross-sectional image and the side pseudo-view in the time dimension are given by using the adjacent interpolation algorithm,the process of producing a complete liquid plug and the process of the liquid structure circulation in the slug flow are observed directly.The characteristics of the flow pattern generation process of agitated flow are from the regular circle in the center of the tube in the gas phase and the ring in the wall of the tube in the liquid phase to the mutual fusion of the gas and liquid phases and the irregular shape.According to the different time required for the liquid structure to pass through the sensor cross section,it is shown that the cycle period is uncertain and the liquid structure is diversified,which explains the reason that the average gas content curve of the sensor cross section decreases and rises rapidly but the cycle fluctuation is not determined.The average gas holdup increases with the increase of the gas phase apparent flow rate and decreases with the increase of the liquid phase apparent flow rate.Compared with churn flow,the gas-liquid interface of slug flow is obvious and stable.The local gas holdup in different regions of liquid plug is different,and the turbulence degree is different.The PDF probability density curve of slug flow is bimodal,located at low gas holdup and high gas holdup respectively,while the PDF probability density function of churn flow is unimodal.Under high gas holdup,the hem width of the curve narrates gradually,and the probability density of the curve increases gradually.At low gas holdup,the peak value becomes lower and the hem of the curve becomes wider.The detailed information of the flow structure of slug flow and churn flow is provided intuitively.