Study On The Applicationin Of ECT Image Reconstruction To Parameter Measurement Of The Two-Phase Flow

Electrical capacitance tomography (ECT) is a novel technology of computerisedtomography brought forward in late1980s, which has a number of capacitiveelectrodes mounted evenly around the periphery of measured insulation material, andmeasures the capacitance value between electrodes to know the distribution ofdielectric constant, thus a kind of visual information can be got about the phasedistribution of closed pipeline section, which is mainly used in detection of two-phaseflow in industrial pipeline. In comparison with the other techniques, ECT has itsadvantages of extensive applicability, being noninvasive, safe to operate. The visibletechnique is of a great developing potential in the two-phase flow parametermeasurement. So the improvement and development of ECT technique is a verysignificant research.More profound study is focused on the key problems such as field distributionmodel of ECT system, electric field characteristic parameters, optimized design ofstructure parameter of sensing array electrode, image reconstruction algorithm. Themain achievements made in this thesis are as follows:1. The mathematical model of sensitivity field is presented according to theprinciple analysis of ECT system and the following study is based on it. The result ofimage recognition proves the model is right.2. Using finite element simulating software ANSYS, the ‘soft-effect’ of sensingfield is analyzed in the ECT system.ANSYS program is written by the ansysparametric design language, and sensitivity field of capacitance sensor is simulated,from the result of sensitivity field analysis, the electric intensity distribution andpotential distribution have been obtained. A novel mixed normalization model withpositive sensitivity ares is put forward to improve the quality of images.3. Sensitivity distribution of the capacitance sensor sensitivity field is studied.The influence of the covering ratio and guards radius on capacitance andsensitive area are analyzed by the finite element method, and optimum design of the electrode architecture is proposed, and the suitable optimization structureparameters are selected by the simulation. Therefore, the accuracy of the sensitivityis improved to make the design of measure circuit easy and design theory of sensorsis perfected.4. To solve the “soft-field” problem of electrical capacitance tomography, amodified Landweber algorithm and a improved niche genetic algorithms arepresented based on the principle of8-electrode ECT system.