Research On The Application Of Electrical Resistance Tomography

Two-phase flow widely exists in industry. The research on two-phase flow is developing rapidly and has been one of the frontier subjects concerned in the world. However, two-phase flow measurement is difficult owing to its complexity. In many cases, its measurement technique is the bottleneck of the development of research on two-phase flow.Electrical resistance tomography (ERT) is a kind of Process Tomography (PT) technology and has the advantages of low cost, simplicity, non-invasion, wide applicability, etc.. ERT has become one of important techniques for two-phase flow measurement. Unfortunately, ERT technique for two-phase flow is still on the stage of laboratory research, though many research works have been reported. There are some problems which should be solved in ERT. The topics of this dissertation are ERT image reconstruction algorithms proposition and application in two-phase flow measurement. The main works are listed as follows:1) The FEM model of ERT is proposed and an ERT software package is developed. The software package has lots of function, such as area dividing, flow pattern setting, the sensitivity coefficient calculating and the ERT forward problem solving.2) Based on the Tikhonov regularization principle and Algebraic Reconstruction Technique (ART) algorithm, a hybrid image reconstruction algorithm for ERT is constructed, which has been used in ECT. Tikhonov regularization principle is introduced to overcome the instability problem of image reconstruction and ART algorithm is used to improve the image quality of the original reconstructed image.3) Based on the optimization principle, a modified BFGS algorithm is proposed. In the new algorithm, an inexact search direction is selected and theHessian matrix of the objective function is replaced with the identity matrix in order to reduce computation and raise image reconstruction speed.4) The two new image reconstruction algorithms are compared with the existing algorithms normally used in ERT of two-phase flow. Experimental results show that the two new algorithms can reconstruct higher quality images. And they are stable and fast. When the image area is divided into a larger number of pixels, the time increment for image reconstruction of the modified BFGS algorithm is smaller than that of other iterative reconstruction algorithms.5) The software for real-time voidage measurement of gas/liquid two-phase flow was developed on the basis of the modified BFGS algorithm. The on-line experiments have been carried out and show that the time for measuring one voidage is less than 0.1 second and the maximum error is less than 8%.