Study On The Forward Problem And Array Electrodes Optimal Design Of Three-dimensional ERT System

ERT(Electrical Resistance Tomography),which characterized by lower costs,non-invasive and visualization,is one of the most promising research subjects in two-phase flow detection fields.At present,research has mainly been focusing on two-dimensional space,with little research on three-dimensional space.However,the three-dimensional information such as the geometrical shape,relative location and space distribution of dicrete phase is needed to get in most cases.In order to realize the three-dimensional observation of the measured field,the study of three-dimensional ERT technology and optimization design of array electrodes is necessary.This thesis was set in the ERT technology,based on the experiments in laboratory and simulations in the finite element analysis software ANSYS and fluid analysis software FLUENT,the array electrodes were analyzed and studied.Explorative research on the multi-objects optimization methods and district three-dimensional tomography algorithm was made based on the solution of forword problem,the simulative and physical experiments were proceeded to verify the optimized results.The main work of this thesis is showed as follow:(1)The mathematical model of ERT system was established based on the assumption of the quasi-static current field,the methods of deducing the system equation using finite element method and calculating the voltage distribution was discussed,the solution of forward problem was completed.(2)According to the same layer and different layers of ERT system sensor with three layers array electrodes,the influences of electrode size,interlayer spacing and the thickness of shielding layer were analyzed on the basis of ANSYS simulation research.(3)Considering the limitation of orthogonal test in three-dimensional ERT senor,Multi-objects optimization algorithms were proposed,including the orthogonal design based on fuzzy math and multivariant nonlinear regression analysis based on uniform design,the parameters of sensor were comprehensive optimized and results were compared and analyzed.(4)A district three-dimensional ERT imaging reconstruction algorithm was proposed for taking away the disadvantages of two-dimensional interpolation algorithm.The algorithm of sensitivity coefficient matrix was improved account of the problems such as dimension increasing,calculation complexity,the speed was increased by more than 10 times afer algorithm imorovement.(5)The gas-solid two phase flow in vertical pipe was simulated in fluid analysis software FLUENT in order to simulating the actual measurement,the output of three-dimensional ERT system was obtained.The optimized sensor structure was verified by comparing the imaing quality.The experiments were proceeded in laboratory,the experimental results were consistent with simulation resluts,which proved the feasibility of three-dimensional ERT in actual measurement situation.In this thesis,three-dimensional ERT system was proposed,the simulative and experimental validation was proceeded using optimized arry electrodes sensor,the results revealed that the correlation coeddicient achieve above 0.6 after optimization.