| The detection to transportation characteristics of oil-air two phase flow in the oil-air lubrication system is an important question to be solved urgently in order to evaluate the lubrication situation. An Electronical Capacitance Tomography (ECT) system, which is aimed at the transportation of oil-air two phase flow in a special small diameter pipeline, is designed and their performance is analyzed in this thesis, and the research work and conclusions are as follows,(1) The sensitivity matrix modeled about a horizontal pipe of the oil-air lubrication system is quickly solved by COMSOL soft, and the soft filed effect of sensitivity filed in this kind of pipe is studied with COMSOL and MATLAB co-simulation software, then the sensitivity matrix and the imaging precision is analyzed under two different situations, one is that the soft filed effect is considered and the other is not, simulating a two-phase pattern of the oil lubrication system in horizontal pipe. The results show that the value of sensitivity field exist a relatively small change when detection electrode is away from oil; however, the value of sensitivity field change obviously when detection electrode is close to oil. In addition, in the process of two-phase flow imaging in a horizontal pipe, the accuracy of image can be further improved when the soft effect is considered.(2) The three-dimensional pipe model on array electrodes is built by COMSOL soft, the potential cloud is obtained under different array electrode structures, the capacitance values of three-dimensional electrodes are solved in the case of empty field and full field respectively, and an expression used to calculate quickly sensitivity filed is derived according to the characteristics of small pipe in oil-air lubrication system. The lateral sensitivity and the sensitivity homogeneity are defined and employed to evaluate ECT’s array electrode characterization of oil-air lubrication system, combining with another two traditional assessments which are the sensitivity and the range of measured capacitance values. The results show that the sensitivity of relatively uniform distribution and better detection sensitivity can be obtained by analyzing characteristics of ECT’s array electrode.(3) Based on the oil-air lubrication system characteristics for small detected pipe, the electrical capacitance tomography with the compensation for capacitance is designed, the key component module in the system is simulated and the algorithmic process is wrote on compensation capacitances. In addition, ECT system is evaluated according to three important assessments. The results show that this system is characterized by short detecting time, the resistance of impurities capacitance, a low distortion about the output.(4) Three methods to digitally extract ECT capacitance values are compared and all capacitance values of three digital demodulations are solved. Then digital quadrature demodulator is selected as the most optimal digital demodulation by four evaluations. The results show that the speed and accuracy of the system are improved more. |
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