Study On The Visualization Measurement Method Of Gas-Water Two-Phase Flow Based On Wire Mesh Sensor (WMS)

Gas-water two-phase flow widely exists in many industry processes.Experimental research on the fluid flow and heat transfer of two-phase flow is of great significance to the efficient use of energy.However,it is difficult to measure two-phase flow parameters due to the complex flow characteristics and the changeable phase interface of gas-water two-phase flow,especially for visualization measurement.At present,the visualization measurement of gas-water two-phase flow includes the methods based on the principle of ray,optics and electronics.The electrical methods are widely used,because of low cost and measuring more parameters.Electrical methods include Electrical resistance tomography(ERT),Electrical capacitance tomography(ECT)and the method based on wire mesh sensor(WMS).Due to the advantages of simple structure,fast imaging,low development cost and so on.WMS method is intensively investigated in recent years.In this paper,the main work is to develop the measurement system based on WMS.Theoretical analysis and simulation calculation were done to ensure the feasibility of the system.Besides,some experiments were designed to verify the functionalities of the system.The paper consists of four parts as follows:(1)Theoretical analysis of the mathematical physical model of WMS.The working mechanism,the structure,the electric field distribution,and the image reconstruction algorithms of WMS are analyzed in detail.(2)Simulation of the WMS based on the ANSYS Maxwell software.The structure of the WMS and the imaging algorithms are researched.For the structure of the WMS,the influence of the wire diameter and the interval distance of wires are studied through emulating the electric field distribution.For the imaging algorithms,the forward problem of WMS is simulated at first.Then,four image reconstruction algorithms are compared.These algorithms include the nearest sampling,the linear interpolation,the cubic interpolation and the spline interpolation.(3)Design and realization of the WMS system.Firstly,a 32×32 WMS measurement hardware is designed including the circuit schematic,the printed circuit board(PCB)and the FPGA firmware.The system is composed of an excitation module,a data acquisition module and a data transfer module.Secondly,the functionalities verification of the switches ADG788,the analog digital converter AD7606 and the ethernet transceiver RTL8211 EG are implemented using oscilloscope.Finally,the software system is achieved.The functions of data acquisition,data storage,and image reconstruction are realized.The image acquisition speed can reach up to 3125 f/s.(4)System verification experiments.An experiment section with size of 34 mm × 34 mm is designed.On the middle of the section,a 16×16 WMS,which has the spatial resolution of 2 mm and the image acquisition speed of 625 f/s,is installed.To verify the correctness of the measurement result,the WMS is compared with a high speed camera(HSC).The results show that the WMS system can visualize the image of gas-water two-phase flow realtimely.