An investigation into the use of a mixture model for simulating the electrical properties of soil with varying effective saturation levels for sub-soil imaging using ECT

Pipelines made of dielectric materials such as Polyethylene (PE) are becoming increasingly popular. With no suitable inspection technique for dielectric pipes, there is an urgent need to develop new technology for their inspection. This paper presents a novel pipe inspection technique using Electrical Capacitance Tomography (ECT) imaging. Traditionally ECT is used for industrial process tomography as a low resolution but fast tomographic imaging technique. Typically commercial ECT can provide a resolution of approximately 10 percent of the imaging region. In this paper a limited region tomography technique is developed take into account prior knowledge about the geometry of the pipe. This has signiflcantly enhanced the imaging resolution of the ECT system, making it a viable pipe inspection solution. The experimental results in this study demonstrate an interior wall loss area as small as 0.195 percent of the ECT cross sectional imaging region is repeatable and can be reliably detected. A narrowband pass fllter method (NPFM) is used as a means to limit the region for the ECT algorithm. This results in an unprecedented resolution, making ECT a viable non-destructive evaluation (NDE) technique for plastic pipes. The NDE application of the ECT for PE pipes is demonstrated in this paper with several experimental results. A wall loss of depth of 1.5mm could be detected for an ECT sensor array of 150mm in diameter, showing a high resolution and high deflnition ECT (HD-ECT) imaging that has not been reported before.

ECT imaging and CFD simulation of different cyclic modulation strategies for the catalytic abatement of hazardous liquid pollutants in trickle-bed reactors

In electrical capacitance tomography (ECT), the electrode-to-gap ratio (EGR) of a sensor is one of the design parameters. It is commonly believed that a larger EGR would result in higher quality of tomographic images. However, no quantitative study has been reported. In this paper, the effect of EGR on ECT imaging is investigated quantitatively. ECT sensors with different EGR of 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 and 10:1 are simulated and images are reconstructed using linear back projection (LBP) and Landweber iteration algorithms for two typical permittivity distributions. The relative image errors are calculated against the real permittivity distributions. The sensitivity distributions of the ECT sensors with different EGR are analyzed and compared. The results show that the effect of ECR on ECT imaging can be neglected when it is larger than 6:1.

Experiments were carried out to monitor the evolution of the deposition of fine particles in trickle-bed reactors during the flow of nonpolar hydrocarbon oil-like liquid suspensions using electrical capacitance tomography (ECT) imaging. The accuracy of the ECT rendition was validated in the pristine (i.e., deposit-free) bed state by comparing the liquid holdup measurements from ECT with the liquid holdup from residence time distribution (RTD) measurements. The pulse-flow characteristics (pulse velocity and frequency) estimated from the ECT signals were in agreement with existing literature data. For filtration experiments, the effects of the initial liquid suspension distribution, the gas and liquid superficial velocities, and single-phase flow (i.e., zero gas velocity) on the structure of the deposition in the bed were studied. ECT imaging successfully tracked the unsteady-state progression of bed plugging throughout the trickle bed. It was found that increasing the liquid or gas superficial velocity res...

Imaging floating metals and dielectric objects using electrical capacitance tomography

Electrical Capacitance Tomography (ECT) system helps user to understand the flow distribution inside the close pipe by detecting the variation of permittivity distribution in the inspection area. Generally, most reported ECT systems are implemented to circular shape pipe only. However, square shape pipes are sometimes found in power industry and chemical reactor, therefore this paper is studying the electrical distribution of ECT system within a square pipe. ECT is able to provide fast response, low cost and non-radiation system but similar to all other electrical tomography system, ECT suffers from soft-field effect. This paper proposes segmentation excitation to overcome this problem. Segmentation excitation applies when more than one electrode excited at one time. This paper focuses Protocol 2 or 2-electrode excitation for 8-electrode square ECT system. The simulation was done by using COMSOL Multiphysics. The images of the excitations are presented in this paper. The electrical potential is recorded at the center of the system to analyses the strength of the electrical potential. In addition for square ECT system, the corner configuration provides 3.40% higher electrical potential compared to side excitation configuration.

Electrical capacitance tomography (ECT) technique has been developed due to its inherent simplicity and low cost. The tomographic images are obtained based on the permittivity differences between the investigated materials and background material (air, in most cases). The dynamic range of capacitance measurements in ECT could be 40 dB or higher. Simultaneously, the changes in the measured capacitances take up only 5% of the full measurement range. Therefore, the capacitance measuring circuit should be of high dynamic range as well as high precision, which constitutes one of the greatest challenges in ECT system design. The standing capacitances in ECT measurements may be canceled by differential measurement. In this paper, a recently developed differential ECT scheme has been presented. An active screen is employed as the differential electrode in the sensor, which is placed between the measuring electrode array and outer screen. Accordingly, a transmitter channel is implemented to accommodate the active screen, which enables the active screen to deliver multi-level AC signal. Simulation and experimental results show that the differential ECT system has a signal-to-noise ratio of 16 dB higher than the previous design, i.e. the non-differential system.

Electrical capacitance tomography (ECT) technique is a new technique for two-phase flow measurement. This paper describes the basic principles of ECT. Forward and inverse problem of ECT are analyzed in detail. The conventional image reconstruction algorithm, i.e., linear back projection algorithm has been given. Then, the new image reconstruction algorithm for ECT based on radial basis function (RBF) neural network has been presented. Using the measurement data obtained from the ECT simulation software developed by the author, the reconstructed images were obtained. Results indicate that RBF neural network is suitable for solving the nonlinear problem of ECT image reconstruction. Comparing with linear back projection algorithm, this algorithm has advantages of higher accuracy.

The Electrical Capacitance Tomography (ECT) imaging pipeline relies on accurate estimation of electric field distributions to compute electrode capacitances and reconstruct permittivity maps. Traditional ECT forward model methods based on the Finite Element Method (FEM) offer high accuracy but are computationally intensive, limiting their use in real-time applications. In this proof-of-concept study, we investigate the use of Graph Convolutional Networks (GCNs) for direct, one-step prediction of electric field distributions associated with a circular ECT sensor numerical model. The network is trained on FEM-simulated data and outputs of full 2D electric field maps for all excitation patterns. To evaluate physical fidelity, we compute capacitance matrices using both GCN-predicted and FEM-based fields. Our results show strong agreement in both direct field prediction and derived quantities, demonstrating the feasibility of replacing traditional solvers with fast, learned approximators. This approach has significant implications for further real-time ECT imaging and control applications.

Chapter 5 Electrical Capacitance, Electrical Resistance, and Positron Emission Tomography Techniques and Their Applications in Multi-Phase Flow Systems

Electrical capacitance tomography (ECT) is a non-destructive imaging technique that aims at visualisation of the permittivity distribution of a dielectric object based on the measured capacitance. Volumetric image reconstruction of three-dimensional ECT is a non-linear ill-posed inverse problem. In this paper, the non-linear iteration steps of a regularised Gauss-Newton method have been implemented to solve the inverse permittivity problem of 3D ECT. The forward problem is solved using the finite element method (FEM). The sensitivity matrices are calculated using an adjoined field formulation. The results are presented based on simulated data with additional simulated noise, showing the importance of 3D modelling and non-linear considerations.

The usage of Electrical Capacitance Tomography (ECT) is not limited to the imaging of mixtures in process equipment, it also can be used to measure the concentration profiles of component, and in certain case ECT is being used to investigate the boundaries and phase sizes within vessels and pipelines. There are quite a number of type of ECT sensors such as circular structure, square structure, concentric -annulus and parallel structure which are used for particular applications. In this paper, a study was carried out in order to investigate the behavior of electric field on the miniature parallel ECT. Simulations using COMSOL Multiphysics are being done to study the effect of increasing the size of the test object and the effect of increasing the permittivity of the test object. The results show that (1) the electric field lines relatively follow the phantom shape corresponding to the increasing of the size of the phantom and (2) the electrical field lines seems to bend more around the when the permittivity increases. Presented simulations establish first step of investigation, however already proved its usefulness for ECT performance model validation.

Many Electrical Capacitance Tomography (ECT) techniques arc utilized recently in many industrial and medical processes. ECT is explored in research from various aspects such as how to reconstruct accurate images of the object under consideration, implantation of real-world recognition systems and/or image viewing devices. In this paper, a novel optimized single-stage fuzzy approach is proposed for reconstructing accurate images to display the materials distribution of the multi-phase flow in industrial pipelines. The proposed algorithm utilizes Fuzzy Inference System (FIS) to overcome the nonlinear response of the ECT system. Genetic algorithm is utilized to optimize the FIS parameters. The proposed optimized single-stage fuzzy algorithm is fast since it does not require solving nonlinear ECT problems to update the sensitivity matrix. The results show that the proposed optimized algorithm has high accuracy and promising features.

Electrical capacitance tomography (ECT) techniques have been developed to visualize industrial processes with dielectric materials. Phase sensitive demodulation is a key part of ECT system to improve speed and accuracy. Methods of demodulation are demonstrated in this paper, including analogue and digital methods. The problems about applying digital quadrature demodulation in ECT were simulated by SIMULINK. Validation shows that the digital phase sensitive demodulation is complete enough to meet the requirements of ECT system in accuracy and speed.

Shape based reconstruction of experimental data in 3D electrical capacitance tomography