Research On 3D Image Reconstruction Of Electrical Capacitance Tomography

Electrical Capacitance Tomography(ECT)is a new type of visual measurement method in the field of multiphase flow detection.In the middle of the 20 th century,with the gradual maturity of computed tomography(CT)technology.The principle of Process Tomography(PT)technology is born,it is also based on sensitivity.ECT technology is a kind of PT technology based on the principle of capacitive sensitivity.Because the technology has many advantages such as low equipment manufacturing cost,non-contact detection,simple operation and high safety,it has become a research hotspot in recent years,and gradually moves from the laboratory to the industrial application field.On the basis of the traditional ECT two-dimensional image reconstruction basic principle,model establishment,algorithm implementation and other processes,this paper uses COMSOL and MATLAB to study the related problems in ECT threedimensional image reconstruction.The main research contents and conclusions are as follows:(1)Optimization design of structural parameters of 3D ECT sensor.The effects of shielding layer radius,layer spacing,plate height and plate width on the sensitivity field uniformity index and the measured capacitance value dynamic range index are analyzed.It is found that each parameter is not a simple proportional or inverse relationship with the two indicators.In the range of values in this paper,there are optimal values.On the basis of this,the orthogonal test method is used to simulate the combination of these four parameters,and a set of better parameter combination schemes is obtained.And using this scheme for image reconstruction,the imaging effect is good.(2)Research on the excitation measurement mode of a three-layer 24-electrode array.The lateral and longitudinal excitation measurement modes of three layers of 24 electrodes were proposed.Six modes of single-electrode excitation single-electrode measurement,two-electrode excitation two-electrode measurement and three-electrode excitation two-electrode measurement were designed.The independent measurement number,capacitance measurement value,uniformity distribution uniformity,uniformity of sensitive field distribution and reconstructed image error of the mode,the performance of the longitudinal three-electrode excitation two-electrode measurement mode is good.(3)Research on 3D ECT image reconstruction algorithm.The linear Back Projection Algorithm,Landweber Algorithm,Conjugate gradient Algorithm and Algebraic Reconstruction Technique are introduced.The image reconstruction process of five typical medium distribution models is realized based on MATLAB software programming.The four algorithms are compared.The algorithm running time,image relative error and correlation coefficient,among which the algebraic reconstruction algorithm performs well in imaging results and evaluation indicators.