Study On ECT Multiphase Flow Measurement System

Multiphase flow is widely used in oil and gas production processes where monitoring the flow pattern,phase content and media distribution in the pipeline is of great importance for the safety and efficiency of the production process.ECT has become an important tool for multiphase flow measurement due to its visibility,non-intrusive,non-interfering,fast imaging speed and low cost,but ECT systems still face problems such as insufficient accuracy of measurement data and artefacts in reconstructed images when measuring multiphase flow parameters.In order to solve the problems of ECT system in multiphase flow measurement,this paper develops the ECT multiphase flow measurement system from hardware circuit design,software development,measurement method,imaging optimization and other aspects.The main research work and results of this paper are as follows:(1)In this paper,we developed an array electrode sensor for ECT multiphase flow measurement system,completed a CDC-based micro-capacitance measurement circuit,realized the electrode switching circuit,ARM control circuit,power supply circuit and other circuits that are compatible with the micro-capacitance measurement circuit,and developed the control program of the hardware circuit.After experimental tests,the relative error of the hardware circuit in measuring the standard capacitance is 0.0054% and the relative standard deviation is0.0078%;the signal-to-noise ratio of each capacitance measurement channel is 40 d B at the minimum and 64 d B at the maximum in the null-full field measurement experiment.(2)We proposed a multi-phase flow pattern identification scheme based on the BPNN model.The scheme extracts features from the capacitance vector that have strong correlation with the flow pattern to construct feature vectors for training and testing the BPNN model.The results show that the trained BPNN model can accurately identify multi-phase flow patterns and investigate the relationship between phase content ratio and capacitance value.(3)We present an optimized model for ECT imaging based on PCNN image fusion,which takes as input the reconstructed images of the Tikhonov regularization algorithm and the Landweber iterative algorithm.The optimized images combine the advantages of the Tikhonov regularization algorithm and the Landweber iterative algorithm,reducing the artefacts at the edges and in the middle of the images,improving the accuracy of ECT imaging,and measuring the phase inclusion rate with high accuracy based on the optimized images.(4)We have developed a simple and functional ECT multiphase flow measurement system based on QT and MATLAB.The upper computer software has the functions of controlling the lower computer,receiving capacitance data,inversion imaging,flow pattern identification,phase content measurement and ECT image optimization.The ECT multiphase flow measurement system has been tested in the laboratory to simulate gas-solid two-phase flow in various flow patterns.The test data showed that the success rate of the ECT multiphase flow measurement system designed in the thesis was 100% for flow pattern prediction and the average relative error of the phase inclusion rate was 4.78%.