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The following list contains our current publications. The most recent publications are located at the top.

2024

Benjamin J Straiton, Matthew A Charleston, and Qussai M Marashdeh

Abstract. Cryogenic fluid flow is a critical measurement parameter but is difficult to properly measure due to the extreme environmental conditions and the frequent presence of multiphase flow during saturated liquid transfers. Multiphase flow proves challenging for most flow measurement methodologies; furthermore, additional measurements of volume fraction, quality, and slip velocity are often required. In-line capacitance-based sensors have the potential to overcome these limitations. In this paper, a capacitance sensor in a multiphase cryogenic flow loop is evaluated for its ability to measure liquid volume fraction, gas phase velocity, and total mass flow rate for two-phase cryogenic nitrogen flow.

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20 June 2024

by Denghong Zhou , Kanat Karatayev Yilin Fan, Benjamin Straiton, and Qussai Marashdeh

Abstract: This work presents an experimental study on oil–water flow downstream of a restriction. The flow pattern, volumetric phase distribution, and their impacts on pressure drop are discussed. We employed two techniques to visualize the oil–water flow patterns, a high-speed camera and an Electrical Capacitance Volume Tomography (ECVT) system. The ECVT system is a non-intrusive device that measures the volumetric phase distribution at the pipe cross-section with time, which plays a critical role in determining the continuous phase in the oil–water flow, and therefore the oil–water flow pattern. In this study, we delved into the oil–water flow pattern and volumetric phase distribution for different valve openings, flow rates, and water cuts, and how they impact the pressure drop. The experimental results have demonstrated a strong relationship between the oil–water flow pattern and the pressure gradient, while the oil–water flow pattern is significantly influenced by the flowing conditions and the valve openings. The impacts of water cuts on the oil–water flow pattern are more obvious for smaller valve openings. For large valve openings, the oil and water phases tend to be more separated. This results in a moderate variation in the pressure gradient as a function of water cuts. However, it becomes more complex as the valve opening decreases. The pressure gradient generally increases with decreasing valve openings until the flow pattern becomes an oil-in-water dispersed flow. The impact of the valve on the pressure gradient is more pronounced in water-dominated flow when the water cut is above the inversion point, while it seems to be most obvious for medium water cut conditions.

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17 October 2023

Shah M. Chowdhury, Matthew A. Charleston, Qussai M. Marashdeh, and Fernando L. Teixeira

Abstract: Propellant mass gauging under micro-gravity conditions is a challenging task due to the unpredictable position and shape of the fuel body inside the tank. Micro-gravity conditions are common for orbiting satellites and rockets that operate on limited fuel supplies. Capacitance sensors have been investigated for this task in recent years; however, the effect of various positions and shapes of the fuel body is not analyzed in detail. In this paper, we investigate this with various fill types, such as annular, core-annular, and stratified fills at different positions. We compare the performance among several curve-fitting-based approaches and a machine-learning-based approach, the latter of which offers superior performance in estimating the fuel content.

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21 July 2022

Rafiul K. Rasel, Shah M. Chowdhury, Qussai M. Marashdeh, and Fernando L. Teixeira

Abstract: Electrical Capacitance Volume Tomography (ECVT) has emerged as an attractive technology for addressing instrumentation requirements in various energy-related multiphase flow systems. ECVT can monitor multiple flow conditions and reconstruct real-time 3D images from capacitance measurements using a large set of electrode plates placed around the processes column enclosing the sensed flow system. ECVT is non-intrusive and allows the measurement of changes in mutual capacitance between all possible plate pair combinations. The objective of this paper is to provide a comprehensive review of recent advances in ECVT, enabling robust monitoring of multiphase flows, especially water-containing multiphase flows.

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1 August 2022

SHAH M. CHOWDHURY, CODY PARK, YASWANTH POTTIMURTHY, QUSSAI M. MARASHDEH, FERNANDO L. TEIXEIRA, AND LIANG-SHIH FAN

ABSTRACT Electrical Capacitance Volume Tomography (ECVT) is a low-cost and high-speed sensing modality with great potential for industrial multiphase flow monitoring. In this work, we examine the use of the slope of the capacitance vector residual curve, as directly provided by the measurement data, to formulate a robust stopping criterion for the iterative image reconstruction in ECVT. The methodology is illustrated based on experimental data from a gas-solid fluidized bed. We show that the proposed stopping criterion can improve the performance of both the image reconstruction and the flow velocity profiling in ECVT applications. For concreteness, we focus on the popular Landweber iterative reconstruction algorithm although other reconstruction algorithms exhibiting semi-convergent behavior might benefit from the present analysis as well.

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8 September 2021

Claas Spille, Vaishakh Prasannan Tholan, Benjamin Straiton, Monika Johannsen, Marko Hoffmann 1, Qussai Marashdeh, and Michael Schlüter

Abstract: Against the background of current and future global challenges, such as climate change, process engineering requires increasingly specific solutions adapted to the respective problem or application, especially in gas–liquid contact apparatuses. One possibility to adjust the conditions in this kind of apparatuses is an intelligent and customized structuring, which leads to consistent fluid properties and flow characteristics within the reactor. In the course of this, the interfacial area for mass
transfer, as well as residence times, have to be adjusted and optimized specifically for the respective application. In order to better understand and advance the research on intelligent customized additively manufactured lattice structures (AMLS), the phase distributions and local gas holdups that are essential for mass transfer are investigated for different structures and flow conditions. For the first time a tomographic measurement technique is used, the Electrical Capacitance Volume Tomography (ECVT), and validated with the volume expansion method and a fiber optical needle probe (A2PS-B-POP) for an air-water system for different modes of operation (with or without cocurrent liquid flow in empty or packed state). The ECVT proved to be particularly useful for both in the empty tube and the packed state and provided new insights into the phase distributions occurring within structured packings, which would have led to significantly underestimated results based on the visual reference measurements, especially for a densely packed additively manufactured lattice structure (5 mm cubic on the tip). Particularly for the modified structures, which were supposed to show local targeted differences, the ECVT was able to resolve the changes locally. The additional use of a pump for co-current flow operation resulted in slightly higher fluctuations within the ECVT data, although local events could still be resolved sufficiently. The final comparison of the empty tube at rest data with a fiber optical needle probe showed that the results were in good agreement and that the local deviations were due to general differences in the respective measurement techniques.

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12 June 2021

Yan-Shu Huang, Sergio Medina-González, Benjamin Straiton, Joshua Keller, Qussai Marashdeh, Marcial Gonzalez, Zoltan Nagy, and Gintaras V. Reklaitis

Abstract: While measurement and monitoring of powder/particulate mass flow rate are not essential to the execution of traditional batch pharmaceutical tablet manufacturing, in continuous operation, it is an important additional critical process parameter. It has a key role both in establishing that the process is in a state of control, and as a controlled variable in process control system design. In current continuous tableting line operations, the pharmaceutical community relies on loss-in-weight feeders to monitor and understand upstream powder flow dynamics. However, due to the absence of established sensing technologies for measuring particulate flow rates, the downstream flow of the feeders is monitored and controlled using various indirect strategies. For example, the hopper level of the tablet press is maintained as a controlled process output by adjusting the turret speed of the tablet press, which indirectly controlling the flow rate. This gap in monitoring and control of the critical process flow motivates our investigation of a novel PAT tool, a capacitance-based sensor (ECVT), and its effective integration into the plant-wide control of a direct compaction process. First, the results of stand-alone experimental studies are reported, which confirm that the ECVT sensor can provide real-time measurements of mass flow rate with measurement error within −1.8 ~ 3.3% and with RMSE of 0.1 kg/h over the range of flow rates from 2 to 10 kg/h. The key caveat is that the powder flowability has to be good enough to avoid powder fouling on the transfer line walls. Next, simulation case studies are carried out using a dynamic flowsheet model of a continuous direct compression line implemented in Matlab/Simulink to demonstrate the potential structural and performance advantages in plant-wide process control enabled by mass flow sensing. Finally, experimental studies are performed on a direct compaction pilot plant in which the ECVT sensor is located at the exit of the blender, to confirm that the powder flow can be monitored instantaneously and controlled effectively at the specified setpoint within a plant-wide feedback controller system.

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2021

Shah Mahmud Hasan Chowdhury

Electrical Capacitance Volume Tomography (ECVT) refers to three-dimensional (3D) imaging of flow media exhibiting two or more material phases in a region of interest (RoI) based on electric permittivity variations. Such multiphase flows are commonly found in industrial settings such as gas-oil-water flow in oil pipelines, gas-solid flows in various chemical processes etc. An ECVT sensor is comprised of metal electrodes flush mounted on an insulating pipe wall surrounding the RoI. They are arranged in a multi-layer pattern being able to capture the 3D variation in permittivity, i.e. both the cross-sectional (xy) and the axial (z) variation. Because of the wall, there exists only capacitive coupling between the electrodes and the RoI, which makes the modality non-intrusive in nature. Other advantages include conformal sensor shape, cheaper electronics due to low-frequency operation, and fast acquisition rate suitable for capturing fast moving flows. The mutual capacitance measured among the electrodes is used, with the aid of an appropriate image reconstruction algorithm, to reconstruct a 3D image of the permittivity distribution corresponding to the actual material distribution in the RoI. A limitation of ECVT is the poor image resolution compared to other imaging modalities, e.g. X-ray, which originates from the ill-posed nature of the inverse problem associated with ECVT. Flow velocimetry has been a topic of interest for decades. A lot of information about a flow can be derived if the velocity profile can be determined. Although ECVT can perform flow imaging, there has not been a convenient way of determining the velocity profile.

Previous efforts include cross-correlating two successive images, which is computationally intensive and not robust as cross-correlation works in very simple cases only. Moreover, errors incurred in image reconstruction are compounded with cross-correlation which makes the situation worse. In this regard, a different velocimetry method is documented in this dissertation which is free of cross-correlation. The method exploits a mapping between the moving flow and the temporal change in capacitance. It formulates a new forward problem, which can be solved using the conventional image reconstruction methods used for imaging. This method overcomes the limitations with the previous cross-correlation based approach, however, it has its own shortcoming. It is more challenging than imaging as it deals with three unknowns, i.e. the velocity components in three axial directions, as opposed to only one unknown for imaging which is the permittivity. The number of known variables is, however, only one for both problems which is the capacitance. This difficulty often degrade the performance of velocimetry as compared to imaging in similar cases, which is documented in terms of simulation results. In addition to that, experimental results are included with various data conditioning methods such as data smoothing, outlier removal etc.

Another contribution documented in this dissertation is the electronic scanning for ECVT, which aims improving the image resolution. For electronic scanning, a high electrode density sensor is employed as compared to a conventional sensor. Then, the electrode segments are connected and reconfigured dynamically to mimic physical rotation and displacement of the sensor on its axis. It is shown that electronic scanning is capable of increasing the resolution over conventional ECVT, however, at the cost of additional acquisition time because of the scanning. In this regard, a number of scanning strategies are described featuring different synthetic electrode shapes, and the optimum one is pointed out considering different acquisition times. Also, the strategies are implemented in SPICE to evaluate their feasibility in circuit aspects, e.g. signal to noise ratio (SNR), as compared to a conventional ECVT sensor. The conclusions derived from this analysis would serve future hardware implementation and testing of electronic scanning with adaptive ECVT sensors. Lastly, a study is included for volume fraction estimation of a two-phase flow based on ECVT capacitance data. The estimated volume fraction is intended to be used as a stopping criterion for an iterative image reconstruction method used throughout this dissertation.

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15 March 2021

Rafiul K. Rasel, Benjamin Straiton, Qussai Marashdeh, and Fernando L. Teixeira

Abstract—Real-time monitoring of water volume fraction in multiphase flows is an important problem for a number of industrial applications. The water phase in the multiphase flows may correspond to either the dispersed phase or the continuous phase. In the past, several low-cost and nonintrusive techniques based on the electrical capacitance tomography (ECT) has been developed to image and monitor in real-time multiphase flows containing water. However, such monitoring becomes increasingly challenging for high salinity levels, and no reliable ECT-based method is presently available which could work for obtaining water volume fraction in multiphase flows for all water salinity levels. In this paper, we propose a new approach based on the Hanai’s formula for complex dielectric constant and taking advantage of the Maxwell-Wagner-Sillars effect to obtain, to a good approximation, water volume fractions in multiphase flows containing water as either dispersed or continuous phase.

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2021

Daniel Ospina Acero, B.S., M.S.

Abstract: Electrical Capacitance Tomography (ECT) and its derived technologies represent one of the preferred mechanisms to study multi-phase flows in industrial applications due to their low cost, relatively fast imaging speed, non-invasiveness, non-intrusiveness and robustness. One important weakness of these technologies, however, is that they are part of what is known as soft-field imaging techniques, where the operating frequencies of the interrogating fields are very low, ultimately resulting in low spatial resolution. In addition, the problem of image reconstruction in ECT defines an inverse problem, which corresponds to a series of particular challenges in the solution process: mainly, lack of uniqueness in the solution, and high degree of numerical instability. This reality in practical applications results in severely underdetermined systems of equations, with particular sensitivity towards random perturbations in the input data. In the last few years there have been numerous efforts to address those difficulties in ECT-based systems, but they essentially can be categorized in two main sets. The first one corresponds to the exploration of different strategies in the algorithms to perform the image reconstruction, and the second one corresponds to different hardware mechanisms to try to obtain more information from the sensing domain. The work that we present in this dissertation deals with both.

In the first case, we employ the Bayesian regression framework configured by the Relevance Vector Machine (RVM) to define an algorithm for ECT applications that can concurrently provide image reconstruction results and uncertainty estimates about the reconstruction. To illustrate the RVM operation in ECT, we simulate typical ECT scenarios, making explicit the connection between the reconstructed pixel values and the corresponding uncertainty estimates in each case. We compare the RVM reconstruction performance with that of the Iterative Landweber Method (ILM) and the least absolute shrinkage and selection operator (LASSO) in all the considered scenarios. The results show that, in addition to the key advantage of providing uncertainty measures, RVM can achieve similar reconstruction results with either lower or similar computational complexity.

In the second case, we introduce an efficient synthetic electrode selection strategy for use in Adaptive Electrical Capacitance Volume Tomography (AECVT), which is a volumetric imaging technology that introduces different changes in the configuration of the sensor to allow for more flexible scanning procedures. The proposed strategy is based on the Adaptive Relevance Vector Machine (ARVM) method and allows to successively obtain synthetic electrode configurations that yield the most decrease in the image reconstruction uncertainty for the spatial distribution of the permittivity in the region of interest. The problem is first formulated as an instance of the Quadratic Unconstrained Binary Optimization (QUBO). By noting that the QUBO formulation is an NP-hard problem and thus prohibitive in practice, we then introduce the Reduced ARVM method, corresponding to the application of the ARVM method to a reduced search space. By using the Reduced ARVM method, good image reconstruction and low uncertainty levels can be achieved in AECVT with considerably fewer measurements. To corroborate our analysis, we present simulation results for three representative AECVT scenarios.

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17 January 2020

Daniel Ospina Acero, Qussai M. Marahsdeh, Senior Member, IEEE, Fernando L. Teixeira, Fellow, IEEE

Abstract—We present a Relevance Vector Machine (RVM) based algorithm for electrical capacitance tomography (ECT) applications that can concurrently provide image reconstruction results and uncertainty estimates about the reconstruction. To illustrate the RVM operation in ECT, we simulate typical ECT scenarios, making explicit the connection between the reconstructed pixel values and the corresponding uncertainty estimates in each case. We compare the RVM reconstruction performance with that of the Iterative Landweber Method (ILM) and the least absolute shrinkage and selection operator (LASSO) in all the considered scenarios. The results show that, in addition to the key advantage of providing uncertainty measures, RVM can achieve similar reconstruction results with either lower or similar computational complexity.

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24 April 2020

Shah M. Chowdhury, Qussai M. Marashdeh, Senior Member, IEEE, and Fernando L. Teixeira, Fellow, IEEE

Abstract: Electrical Capacitance Volume Tomography (ECVT) has been applied for imaging of multiphase flows found in industrial applications. The ill-posed nature of the image reconstruction problem in ECVT and the consequent low resolution can be alleviated by employing electronic scanning enabled by electrode segmentation and reconfiguration during data acquisition. Here we study electronic scanning strategies that mimic physical rotation and shifting of the sensor along its symmetry axis. First, we study the feasibility of electronic scanning by analyzing the capacitance transducer circuit in SPICE. Then, we simulate electronic scanning using the finite element method for different electrode shapes, for which we compare the image reconstruction results and acquisition time. We find a noticeable improvement in image resolution for the scanning cases over conventional ECVT. Finally, among the scanning cases, we emphasize a particular electrode shape that provides the best image resolution along with the minimal amount of acquisition time.

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25 December 2020

Daniel Ospina Acero, Shah M. Chowdhury, Student, IEEE, Qussai M. Marashdeh, Senior Member, IEEE, and
Fernando L. Teixeira, Fellow, IEEE

Abstract: Electrical capacitance tomography is a widely used sensor modality for flow imaging in many industrial settings. Adaptive electrical capacitance volume tomography (AECVT) extends the capabilities of traditional ECT by enabling direct volumetric imaging and an improved resolution. Construction of the sensitivity matrix is a necessary step to obtain flow images. This step requires the computation of the electric field inside the sensing domain, which is done via a typical field solver, such as the finite-element method. In this work, we present an efficient and flexible method to construct the sensitivity matrix for AECVT based on individual electrode segment excitations and their judicious combination to form desired matrix elements. We illustrate how the proposed method yields the same sensitivity matrix as the traditional method but at a much lower computational cost. Once all segment contributions are obtained, we also indicate how the proposed method, unlike the traditional approach, can generate the sensitivity matrix on demand for an arbitrary combination of synthetic electrodes and obviating the need for any additional field computations. Finally, we present image reconstruction results for two different experimental scenarios where the mutual capacitance data and the corresponding sensitivity vectors are obtained through the proposed measurement combination scheme.

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17 December 2019

Qussai Marashdeh

Abstract: The Phase I development of the 4Phase GS Flow Meter for Pulverized Coal saw the successful development of a mass flow algorithm for gas-solids flow. The algorithm saw success measuring the volume fraction, velocity, and mass flow of solid particles at volume fractions below 1%. A weather proof DAS that allows for the operation of an ECVT system in hot, humid, and dusty environments was also designed. All tasks outlined in the Phase I proposal have been successful completed. The ECVT system developed in Phase I is now ready to be tested on a pilot scale coal pulverizer system.

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12 December 2019

Qussai Marashdeh

Abstract: Phase IIA was focused on completing technically challenging aspects of Phase II related to algorithm development, feature extraction, and complete system testing. Our work in Phase II successfully addressed the technical challenge of developing a DAS for the advanced adaptive technology of AECVT. The scope in Phase II included initial tasks related to algorithm development and feature extraction toward the full implementation of a working prototype. However, due to the increased complexity of DAS, we had to adopt an alternative design to what was initially proposed. The advanced design included using multiple Field Programmable Gate Arrays (FPGA’s) where each FPGA needs to be designed for compatibility with other electronic components, simulated, inspected after fabrication, and programmed for receiving plate activation patterns from the software and report back flow measurements. This advanced design required more time and resources than initially planned. With a successfully designed and tested Adaptive DAS ready, work on Phase IIA was able to move forward into firmware design, software design, sensor design, data collection, and algorithm development.

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14 June 2019

Rafiul K. Rasel, Student Member, IEEE, Joshua N. Sines, Qussai Marashdeh, Senior Member, IEEE, and Fernando L. Teixeira, Fellow, IEEE

Abstract: Electrical capacitance tomography (ECT) is a widely used imaging modality to image two-dimensional cross sections of multiphase flows. Recent developments in electrical capacitance volume tomography (ECVT) have made it possible to directly obtain volumetric images from measured data. An ECVT is instrumental for obtaining accurate phase hold up information and velocity information that are needed for the optimization of certain flow processes. However, compared to ECT, the high correlation between the measurements in ECVT exacerbates the ill-conditioning of the associated image reconstruction problem. Previous studies have suggested that neglecting mutual capacitance data between the ECVT electrodes located at cross-planes that are well separated along the sensor axis can be done without significantly affecting the reconstructed image. In addition, this may help constrain the ill-conditioning of the reconstruction problem. Here, we examine in detail and quantify the effect of reduced cross-plane acquisition strategies for optimizing the image reconstruction and constraining the ill-conditioning of typical ECVT settings.

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09-12 January 2019

Rafiul K. Rasel, Daniel Ospina Acero, Fernando L. Teixeira

Abstract: Process tomography is a well-established imaging modality to monitor a variety of flow processes in industrial applications. Traditionally, this has been done through imaging of a cross section of the domain. In recent years, much interest has been devoted to volume process tomography, where a three-dimensional reconstruction is directly obtained. However, depending on the sensor design, the number of independent measurements can be much higher in volume tomography compared to its two-dimensional counterpart. This makes the reconstruction problem more challenging and may prevent real-time monitoring in certain cases. In this work we investigate the optimal choice of cross-layer measurements to provide accurate volumetric tomography while minimizing image reconstruction costs using electrical capacitance volume tomography as example.

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October 2019

Joshua N. Sines, Soohwan Hwang, Qussai M. Marashdeh, Andrew Tong, Dawei Wang, Pengfei He, Benjamin J. Straiton, Christopher E. Zuccarelli, Liang-Shih Fan

Abstract: A novel approach to studying dynamic three phase systems using Electrical Capacitance Volume Tomography (ECVT) is proposed and verified against previously published pressure gauge techniques and hydrodynamics patterns. In this three-phase study, hold up of water, glass beads, and air are measured simultaneously in a slurry bubble column reactor. Application of ECVT to investigate three phase systems holds several advantages over pressure gauges including the ability to deliver non-invasive real time direct measurements without making assumptions about the hydrodynamics. Results support the conclusion that ECVT can be used in place of pressure gauges to obtain accurate holdup measurements of three-phase flow systems in real time applications.

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09-12 January 2019

Daniel Ospina Acero, Shah M. Chowdhury, Fernando L. Teixeira,

Abstract: We apply the Adaptive Relevance Vector Machine to automatically select the measurement set in a tomographic setting, from all the arrangements or combinations of the measuring elements, that yield the lowest level of uncertainty about the estimated results, while maintaining good image reconstruction. To illustrate the proposed method, we present simulation results derived from Electrical Capacitance Tomography.

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09-12 January 2019

Shah M. Chowdhury, Rafiul K. Rasel, Fernando L. Teixeira

Abstract: In this paper, a soft-field tomography-based velocity profile reconstruction is conducted for different two-phase flow models. The method is based on the use of the sensor sensitivity gradient in the region of interest based on a Laplacian interrogating field. The described method offers a robust and reliable velocity profile measurement over earlier cross-correlation-based methods.

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21 July 2020

Joshua N. Sines, Benjamin J. Straiton, Christopher E. Zuccarelli, Qussai M. Marashdeh, Fernando L., Teixeira, Liang-Shih Fan, and Brian J. Motil

Abstract: Passive cyclonic gas-liquid separators (PCGLSs) are commonly used in microgravity conditions where gravity settling separation is difficult or impossible. In this study, displacement-current phase tomography (DCPT) is used to measure various features of the gas-liquid flow inside of a PCGLS. The liquid holdup, liquid angular velocity, and gas core size are investigated. The liquid holdup is also measured in a gas-liquid flow that simulates the injection flow for a PCGLS. It is found that the gas core contracts and expands in a periodic motion as air is injected with water. This motion becomes more noticeable as the air flow rate is increased. It is also found that the liquid layer angular velocity has a positive linear trend with the air flow rate under constant water flow rates. A basic linear relation is derived to relate the liquid angular velocity to the air and water flow rates. All DCPT and electrical capacitance phase tomography (ECVT) results closely match the visual confirmation methods used for each flow feature.

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2018

Joshua N. Sines, Benjamin J. Straiton, Christopher E. Zuccarelli, Qussai M. Marashdeh, Fernando L. Teixeira, Liang-Shih Fan, and Brian J. Motil

Abstract:  Passive cyclonic gas-liquid separators (PCGLSs) are commonly used in microgravity conditions where gravity settling separation is difficult or impossible. In this study, displacement-current phase tomography (DCPT) is used to measure various features of the gas-liquid flow inside of a PCGLS. The liquid holdup, liquid angular velocity, and gas core size are investigated. The liquid holdup is also measured in a gas-liquid flow that simulates the injection flow for a PCGLS. It is found that the gas core contracts and expands in a periodic motion as air is injected with water. This motion becomes more noticeable as the air flow rate is increased. It is also found that the liquid layer angular velocity has a positive linear trend with the air flow rate under constant water flow rates. A basic linear relation is derived to relate the liquid angular velocity to the air and water flow rates. All DCPT and electrical capacitance phase tomography (ECVT) results closely match the visual confirmation methods used for each flow feature.

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19 January 2018

Dawei WangMingyuan XuQussai MarashdehBenjamin StraitonAndrew Tong, and Liang-Shih Fan

Abstract: A three-dimensional ECVT sensing technique is applied to imaging complex slugging phenomena of a gas–solid fluidized bed under ambient and elevated temperature conditions. The study indicates that the time interval between rising slugs decreases with an increase in the gas velocity, reaching a nearly steady time interval value of about 1 s between two slugs when the gas velocity is ∼1.7 m/s above the minimum fluidization velocity. The fluidized bed behaves as a bubbling fluidized bed at low gas velocities. In slugging regime, the slug rise velocity increases with the gas velocity. A mechanistic analysis of forces around the dense phase solid particles suggests that the relationship between the slug rise velocity and the gas velocity for the square-nosed slugging bed is not strictly linear and is highly related to the interparticle forces, internal friction of particles, and gas velocity in addition to the wall stress.

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March 2018

Justin M. Weber, Michael M. Bobek, Ronald W. Breault, Joseph S. Mei, Lawrence J. Shadle

Abstract: There is a paucity of riser data for industrial scale units, particularly with regard to the solids fraction. This is especially true for detailed spatially distributed values. To alleviate this problem, NETL installed a 0.445 m tall electrical capacitance volume tomography (ECVT) sensor 9.66 m from the gas distributor of its industrial size (15.45 m high and 0.3 m diameter) circulating fluidized bed (CFB) cold model. A series of tests were conducted to investigate the gas-solid flow behavior using high density polyethylene (PPE) solids. Static electricity was successfully minimized using Larostat and humidification. Time averaged radial solid fractions profiles are presented and discussed. The time and spatially averaged solid fractions measured by the ECVT agree well with estimates from the pressure drop. The annular thickness was measured and found to increase with increases in the solids flow rate and decrease with increases in the gas velocity. Comparisons of the annular thickness and solids fraction as determined from the ECVT unit were compared to existing correlations. The average error ranged from 13% to 275% which is not surprising since the literature correlations were developed from data on much smaller units and for significantly different particles.

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March 2018

Chris Zuccarelli, Benjamin Straiton, Joshua Sines, Qussai Marashdeh

Abstract: Displacement Current Phase Tomography (DCPT) is a real-time 3D imaging and measurement technique for the online study of multiphase flow behavior. Here, it is applied for the study of a bubbly, two-phase flow of gas and water. A straight cylindrical column was constructed and an experiment conducted where the air mass flow rate through the column was varied. A DCPT system was used to capture real-time, three-dimensional data about the bubbly flow, and this data was analyzed to determine important factors about the bubbly flow, such as void fraction, bubble size, bubble frequency, and bubble velocity.

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March 2018

Chris Zuccarelli, Benjamin Straiton, Joshua Sines, Qussai Marashdeh

Abstract: Electrical Capacitance Volume Tomography (ECVT) is a real-time 3D imaging and measurement technique for the online study of multiphase flow behavior. Here, it is applied for the study of two fluidized beds, one with Geldart Class A particles and another with Class B particles. A straight cylindrical column was constructed and an experiment conducted where the air mass flow rate through the column was varied. An ECVT system was used to capture real-time, three-dimensional data about the fluidized beds, and this data was analyzed to determine important factors about the fluidized beds, such as void fraction, bubble size, bubble frequency, and bubble velocity.

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11 February 2018

Joshua Sines, Benjamin Straiton, Christopher Zuccarelli, Qussai Marashdeh

Abstract: Electrical Capacitance Volume Tomography (ECVT) is a real-time 3D imaging and measurement technique for the on line study of multiphase flow behavior. Here, it is applied for the study of a static three phase oil-water-gas system. A cylindrical test column was constructed and an experiment conducted where the air and water volume fractions were varied in an oil continuous background. An ECVT system was used to capture real-time data about the system and this data was analyzed to determine the volume fraction of the three phases and analyze the systems accuracy in determining these volume fractions.

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8 October 2018

Rafiul K. Rasel, Qussai Marashdeh , and Fernando L. Teixeira, Fellow

Abstract: Imaging of multiphase flows holding water as continuous phase (i.e., water-dominated flows) is very challenging for conventional electrical capacitance tomography (ECT) due to the high permittivity of water. In this paper, we introduce a new approach, based on the multi-frequency excitation of ECT sensors, for imaging and real-time monitoring of water-dominated columnar or slug vertical flows. The proposed method exploits differences between measurements obtained at distinct frequencies caused by the Maxwell-Wagner-Sillars effect, which is present in multiphase flows with at least one conducting phase. To illustrate this new approach, several numerical simulations are carried out for two-phase and three-phase mixtures containing air, methylamine, and/or oil as dispersed phases and with water as the continuous phase. Experimental results are also provided to validate the findings.

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15 February 2018

Shah Chowdhury, Qussai M. Marashdeh2, and Fernando L. Teixeira

Abstract: Proper normalization of the measured capacitance data is a prerequisite in electrical capacitance tomography (ECT). Conventional methods, such as parallel and series normalization, assume a higher permittivity perturbation in a homogeneous (lower) permittivity background. Although this is applicable to a number of cases, some two-phase flows are better modeled instead as a lower permittivity perturbation in a homogeneous (higher) permittivity background. A different normalization method is proposed for such cases, which provides similar image quality as conventional but is particularly beneficial for velocimetry applications based on sensitivity gradient of the ECT sensor. Simulation and experimental results are provided to illustrate the advantages for the proposed normalization technique.

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25 November 2018

Cagdas Gunes, Shah M. Chowdhury, Christopher E. Zuccarelli, Qussai M. Marashdeh, and Fernando L. Teixeira

Abstract: Displacement-current phase tomography (DCPT) is a process tomographic technique originally proposed to overcome the limitations of electrical capacitance tomography (ECT) for two-phase flows where one phase is electrically conductive such as water. Both DCPT and ECT are 2D cross-sectional imaging techniques. In this paper, two new developments based on DCPT are described. First, we describe the extension of DCPT to perform direct volumetric imaging. Second, a new method for fluid flow velocimetry (3D velocity profiling) based on volumetric DCPT is proposed. The simulation and the experimental results are provided to demonstrate the proposed techniques for the imaging of water-dominated vertical flows.

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29 June 2018

Zeeshan Zeeshan, Christopher E. Zuccarelli, Daniel Ospina Acero, Qussai M. Marashdeh, and Fernando L. Teixeira

Abstract: Electrical capacitance tomography (ECT) exhibits several attractive features that are important for industrial process tomography applications. These features include low cost, high speed, and nonintrusive nature. However, due to its soft-field character, a relatively low image resolution is an outstanding challenge for ECT. While many efforts have been made to tackle this challenge by improvements in image reconstruction algorithms, relatively less has been done to enhance the basic ECT hardware sensor configuration and data acquisition process. In this paper, a new measurement acquisition strategy is introduced to increase image resolution when using adaptive ECT (AECT). The proposed strategy is based on the manipulation of synthetic electrodes plates (“metaplates”) formed by a set of combined smaller physical electrodes (segments). The synthetic electrodes are sequentially activated with partial overlap of constituent segments to provide a fine-stepped axial and/or azimuthal electronic scan along the entire sensor. Consequently, an increased number of independent capacitance measurements are made available. Reconstruction results using the proposed measurement acquisition strategy (AECT) are shown to illustrate the enhanced resolution and stability in the imaging of objects compared to conventional ECT sensors.

Link

2018

Cagdas Gunes

Abstract: Process tomography is the investigation and imaging of a physical process in region of interest (RoI), such as fluid flow for example, on time and spatial scales around those of the process dynamics. The data gathered from the RoI may be utilized for diverse purposes such as characterization of industrial monitoring and control, design and optimization of industrial hardware, combustion flame imaging, and flow imaging, to name just a few. Due to nature of these applications, the associated sensors often need to be operated in harsh environments under very high pressure and/or temperature conditions. This reduces the currently available sensing modalities to a handful of choices as the possible candidates. Among these modalities, electrical capacitance tomography (ECT) holds great potential due to its relatively fast, non-invasive, nonintrusive imaging characteristics in addition to lightweight and inexpensive hardware. These attractive characteristics also carry over to electrical capacitance volume tomography (ECVT) which find applications in petroleum, chemical, and biochemical industries. Despite all these benefits, ECT and ECVT systems also have a few challenges that demand research efforts. First, typical operational frequencies are below 10 MHz, which make these “soft-field” modalities yield relatively low resolution compared with “hard-field” imaging counterparts such as X-ray. Second, current hardware design imply a high degree of correlation between mutual capacitance measurements and therefore an highly ill-conditioned inverse (imaging) problem. In addition, with the increasing demand for volume tomography, more challenging applications are being sought after by industry such as exploration of larger RoI with better resolutions. Therefore, these scenarios imply increased computational costs for the volumetric imaging problem and make it more difficult real-time ECVT imaging applications. In this dissertation, we introduce displacement-current phase tomography (DCPT) for process tomography. The operation principle of DCPT is based on the imaging of the imaginary part of the permittivity inside the RoI, which is complementary to real-part permittivity imaging obtained by ECT. While using the same ECT hardware, DCPT provides better resolution for certain classes of applications involving lossy media. This method is also extended to 3D volume tomography based on the use of ECVT hardware. DCPT is also extended to velocimetry applications, where the objective is to image the flow velocity in the RoI, based on ECVT hardware. Finally, a faster reconstruction approach for ECT/ECVT systems based on sparse representation of images in the Fourier domain is proposed and studied to facilitate real-time imaging for applications involving volumetric RoIs.

Link

2018

Cody Park

Abstract: The chemical looping process is a novel process platform capable of efficiently converting fossil fuels to energy or chemical products with in-situ carbon capture. The process may be designed for a variety of fuel feedstocks, from coal and biomass to natural gas, and can yield a flexible range of products such as syngas and electricity. In the process, a metal oxide oxygen carrier oxidizes a fuel source by providing lattice molecular oxygen in one reactor. The depleted oxygen carrier is transported to a second reactor where it is re-oxidized with air and transported back to the first reactor in a cyclic manner. The process then results in a pure product or flue gas stream while circumventing the need for air separation units or carbon separation units associated with other carbon capture techniques. As the chemical looping platform approaches commercial deployment, the need for an advanced process control architecture is made evident. Experience from operation of several sub-pilot and pilot scale units by The Ohio State University has revealed that the operating parameters of the chemical looping process are highly intertwined and non-linear in nature. In particular, transient state changes experienced during start-up and shut-down of the process is particularly difficult and will only grow increasingly complex as the process is scaled up.

The purpose of this work is then to develop control techniques, algorithms, and architecture for controlling the chemical looping process. Sliding Mode Control is investigated as a superior alternative to classical control methods for non-linear control loops in terms of both control properties as well as ease of implementation. The controllers are tested and compared against Proportional-Integral control for regulation of the system pressure, pressure balance, non-mechanical gas seals, and solids circulation rate of a Syngas Chemical Looping sub-pilot unit. The start-up, fuel injection, and shut-down procedures are automated and tested multiple times in the sub-pilot unit, enabling complete automation of the process. Electrical Capacitance Volume Tomography technology is developed as an option for monitoring the solids circulation rate in the chemical looping system, a critical parameter for precise control of the process. Electrical Capacitance Volume Tomography is a non-intrusive, non-invasive process flow measurement technique, capable of providing real-time volume images of two phase flow systems. In this work, experiments and data analysis methods are developed for the imaging and measuring of packed moving bed flow at ambient conditions and elevated temperatures. A method is developed for measuring mass flow and flux through a sensing region. Finally, future work for advanced control development and Electrical Capacitance Volume Tomography is proposed.

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2017

Qussai Marashdeh, Teixeira, and OSU Graduate Students

Abstract: Electrical Capacitance Volume Tomography (ECVT) is a 3D imaging technique for Multi-phase flow measurement. ECVT is among few know non-invasive imaging tools that can be used for commercial applications (low cost, suitable for scale-up,
fast, and safe). Three-Phase flow systems are used in many energy processes. A high temperature ECVT system and sensor was developed and fabricated for testing and demonstration.

Link

19-26 August 2017

Shah Chowdhury, Cagdas Gunes, Qussai M. Marashdeh, and Fernando L. Teixeira

Abstract: The use of electrical capacitance volume tomography (ECVT) is discussed for fast velocity profile imaging associated with two-phase flows in industrial processes. Different combinations of reconstruction algorithms are evaluated by comparing the resolutions obtained and the reconstruction times. A suitable combination of reconstruction techniques is recommended to produce fast but accurate results.

Link

19-26 August 2017

Cagdas Gunes, Shah Chowdhury, Qussai M. Marashdeh, and Fernando L. Teixeira(1)

Abstract: Electrical Capacitance Tomography (ECT) is an imaging modality for spatial reconstruction of the dielectric permittivity distribution inside a region of interest (RoI). ECT utilizes mutual capacitance measurements obtained from electrode sensor pairs placed on a dielectric vessel surrounding the RoI. Displacement-Current Phase Tomography (DCPT) is a variant technique based on the phase information of capacitance measurements enabled by the same harware as ECT. DCPT is predicated on having the sensor plates excited by time-harmonic signals in the quasi-static regime, as commonly done in ECT. Under the presence of lossy media in the RoI, it can be shown that DCPT has an extended linear range (versus ECT) for the dependency between the measurement data and the spatial distribution. This result, together with the fact that no electrical contact is necessary unlike electrical impedance tomography (EIT), makes DCPT, either separately or in combination with ECT, a suitable modality for the reconstruction of lossy media distributions. In this summary paper, we present a comparison between DCPT and ECT results for the imaging of air-water flow systems.

Link

22 September 2017

Rafiul K. Rasel, Cagdas Gunes, Qussai M. Marashdeh, and Fernando L. Teixeira

Abstract: We introduce a method based on the Maxwell-Wagner-Sillars (MWS) effect to improve the performance of displacement-current phase tomography (DCPT) applied to two-phase flow imaging. DCPT utilizes as set of mutual admittance measurements between electrodes placed around a region of interest (RoI). This measurement can extract the phase of the displacement current between the electrodes so as to characterize the spatial distribution of the conductivity or dielectric loss inside the RoI. By exploiting the fact that the measured data at different frequencies will exhibit distinct MWS effects, the proposed approach can extract additional information from the measure data set and improve the resolution of DCPT for the imaging of two-phase flows. Numerical simulations along with experimental results illustrate the main findings of this paper.

Link

27 March 2017

Rafiul K. Rasel, Christopher E. Zuccarelli, Qussai M. Marashdeh, Liang-Shih Fan, and Fernando L. Teixeira

Abstract: We describe an approach, based on electrical capacitance tomography (ECT) sensors, to decompose and continuously monitor multiphase flow components (fractional areas or volumes) in mixtures containing conducting phases. The proposed approach exploits the Maxwell-Wagner-Sillars effect at distinct frequencies to reconstruct each phase of a multiphase flow and is also utilized to estimate the fractional volume of the various phases of the mixture. The approach is illustrated for a three-phase mixture composed of air, water, and oil. This approach utilizes the very same ECT measurement apparatus used for flow imaging and, as such, inherits its high speed of acquisition and suitability for real-time operation.

Link

23 May 2017

Cagdas Gunes, Qussai M. Marashdeh, and Fernando L. Teixeira

Abstract: We compare electrical capacitance tomography (ECT) and displacement-current phase tomography (DCPT) results for non-invasive imaging of lossy media. ECT is based on mutual capacitance measurements between electrode pairs surrounding the region of interest (RoI), whereas DCPT is a relatively less mature sensing modality that utilizes the phase information inherent in the displacement current measured by such electrode pairs excited by time-harmonic voltages (in the electroquasistatic regime). DCPT and ECT can be implemented using basically the same hardware components and used alongside to provide complementary information for imaging purposes or separately to reconstruct the spatial distribution of the loss tangent or the permittivity within the RoI, respectively. We show that the (nonlinear) relationship between the measured phase in DCPT and the conductivity distribution in the RoI has a more extended linear range than the nonlinear relationship between the measured capacitances in ECT and the permittivity distribution in the RoI. Of note, DCPT does not require electrical contact with the RoI in contrast to electrical impedance tomography. To illustrate the potential of DCPT, we evaluate its performance using both numerical examples and experiment results.

Link

2017

Zeeshan, B.E., M.Sc., M.S.

Abstract: Electrical Capacitance Tomography (ECT) is a sensing modality commonly used to find the dielectric permittivity distribution inside a region of interest (RoI) from the boundary electrode capacitance measurements. ECT find applications in various industrial processes due to its low-cost and noninvasive/nonintrusive nature. The ECT reconstruction problem is inherently nonlinear, and the imaging resolution is limited by the soft-field nature and limited number of measurements (due to minimum electrode size constraints to provide a given SNR) enabled by the capacitance measurement system. In order to increase the number of measurement without degrading SNR, adaptive electrical capacitance tomography (AECT) and its 3-D variant adaptive electrical capacitance volume tomography (AECVT) are introduced. The proposed adaptive strategy is based on the manipulation of synthetic electrodes comprised of a set of smaller physical electrodes (segments) enabled by AECT/AECVT hardware. AECT increases the number of measurements; however, the increased amount of correlation between different measurements makes the inverse problem (image reconstruction) more ill-conditioned. Spatially adaptive reconstruction techniques (SART) are introduced that take advantage of the Laplacian nature of the interrogating field in AECT/ECT by utilizing synthetic electrodes based on different segment partition sizes while reconstructing in different portions of the RoI. The reconstruction can be sequentially performed starting from the peripheral region of ii the RoI, where the achievable resolution is higher, towards the center region of the RoI. SART also makes it possible to use different AECT sensing modes together to achieve higher spatial and radiometric resolution as well as to ameliorate some the nonlinear artifacts. The simultaneous activation of multiple electrodes can be advantageous to manipulate the sensing field distribution and capture more spatial information for imaging purposes. However, conventional methods for sensitivity map computation in ECT are inadequate in the presence of multielectrode activation because the mutual coupling between electrodes is not properly accounted for. This coupling becomes especially critical in adaptive electrical capacitance volume tomography (AECVT) sensors, where signals from many small electrode segments are combined into synthetic electrodes. To address this issue, a more general approach is presented for sensitivity map computation in AECVT.

Link

2017

Mingyuan Xu

Abstract: Electrical capacitance volume tomography (ECVT) is a novel 3-D imaging technology for multiphase flow systems. It can capture dynamic flow behaviors in real time and with sufficient fidelity, which can be useful for laboratory fluid mechanics studies as well as industrial process monitoring and diagnosis. To date, ECVT has been successfully applied to various multiphase flow systems, including gas-solid fluidized bed, gas-liquid bubbling bed, gas-solid-liquid trickle bed and flow systems with complex geometries. However, since ECVT was initially developed only for cold flow systems, most of the experiments are conducted at ambient temperature. High-temperature applications of ECVT are greatly desired since most industrial processes operate at elevated temperatures. For example, it is proposed to use ECVT for imaging solid flow at 1000 °C in chemical looping systems to provide real time solids circulation data. To explore the possibilities of employing ECVT at high temperatures, a special heated fluidized bed test unit is built with ceramic inner lining in the ECVT sensor assembly, which protects the sensor from excess heat at high temperatures.

Work in this thesis is focused on studying the slugging phenomenon at different temperatures in the fluidized bed test unit with Geldart D chemical looping oxygen carrier particles as the fluidized solid and air as the fluidizing gas. It not only serves to evaluate the performance of ECVT at high temperatures, but also to examine the effect of temperature on slugging fluidized bed behaviors. Little research has been published on this topic due to the difficulty of fluidized bed characterizations at high temperatures. The experiments were conducted at temperatures ranging from 25 °C to above 700 °C. The results show that slug rise velocity and frequency increase as gas velocity increases, which is consistent with literature data and theory. The results also show that the effect of temperature on the correlation between gas velocity and slug properties is minimal. In addition, a preliminary test for solids circulation rate measurement is conducted in the test unit to explore the proposed application of ECVT in chemical looping. Future plans for the test unit and continuing research on the slugging behavior are also proposed.

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23 September 2016

Shah Chowdhury, Qussai M. Marashdeh, and Fernando L. Teixeira

Abstract: Velocity profiling of a flow involves the task of determining the velocity vector at every point in a given flow volume. A new method is proposed for velocity profiling of multiphase flows based on electrical capacitance volume tomography (ECVT) sensors. The proposed method utilizes a mapping between the change in measured capacitances and the displacement of flow that is effected by the spatial gradient of the sensitivity distribution. This novel mapping not only avoids the need for costly image cross correlations but also is fully compatible with existing ECVT sensor and image reconstruction algorithms. Simulation and measurement results are provided to demonstrate the proposed method.

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17 February 2016

Aining Wang, Qussai Marashdeh, and Liang-Shih Fan

Abstract: Passive cyclonic gas–liquid separators (PCGLSs) have unique advantages compared with other types of gas–liquid separators. In this study, liquid distribution inside a horizontally installed PCGLS is investigated using electrical capacitance volume tomography (ECVT). The liquid distribution is measured under various gas and liquid flow rates. It is found that the inlet liquid flow rate is the dominating factor influencing the liquid distribution. The angular velocity of the liquid layer is found to be proportional to the liquid flow rate when no gas is injected. The center axis of the gas core is observed to be lower than the center axis of the separator cylinder, and it will drift towards the separator׳s center axis with increasing liquid flow rate. A mechanistic model is derived, and flow field parameters are solved analytically to qualitatively explain this phenomenon. The calculated gas core positions match the ECVT images well.

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2015

Z. Zeeshan, F.L. Teixeira and Q. Marashdeh

Abstract: Electrical capacitance tomography (ECT) is a low-cost, high-speed imaging technique useful in many industrial settings. ECT is predicated on the knowledge of sensitivity maps between capacitance electrodes that blanket the imaging domain. The simultaneous activation of multiple electrodes can be advantageous to manipulate the resulting field distributions and capture additional spatial information for imaging purposes. However, conventional methods for sensitivity map computation in ECT are not adequate in the presence of multielectrode activation because the mutual coupling between electrodes is not properly accounted for. This coupling becomes especially critical in adaptive electrical capacitance volume tomography (AECVT) sensors, where signals from many small electrode segments are combined into synthetic electrodes. A more general approach is presented for sensitivity map computation in AECVT based on the actual posteriori (induced) charge distributions rather than the conventional approach based on boundary conditions with no account for electrode interactions.

Link

1 January 2015

Aining Wang, Qussai M. Marashdeh2, Fernando L. Teixeira3, and Liang-Shih Fan

Abstract: Spatial resolution represents a key performance aspect in electrical capacitance volume tomography (ECVT). Factors affecting the resolution include the “soft-field” nature of ECVT, the number of capacitance channels used, the ill-conditioned nature of the imaging reconstruction problem, and the signal-to-noise ratio of the measurement apparatus. In this study, the effect of choosing different numbers of capacitance plates on the performance of ECVT is investigated. Specifically, two ECVT sensors with 12 and 24 capacitance channels but covering equal volumes of a cylinder are used to examine the resulting impact on the image resolution.

Link

2015

Aining Wang

Abstract: Electrical capacitance volume tomography (ECVT) is a novel non-invasive process tomography technique which can provide phase distribution information inside the imaging domain. Compared with other radiation based or magnetic resonance based process techniques, the cost of ECVT is very low, and it has high imaging speed. Compared with conventional electrical capacitance tomography, ECVT can deliver 3-D images and can accommodate to the imaging domains with irregular geometries. In the current study, ECVT is applied to various multiphase flow systems; the feasibilities of ECVT are demonstrated, and the limitations are discussed.

The major limitation of capacitance based tomography techniques is the low spatial resolution. One possible improvement approach is to increase the number of capacitance plates. In the current study, after introducing the basic principle of ECVT, a 24 channels ECVT sensor is compared with a 12 channels sensor. Different static solid objects are imaged by both sensors, and the results indicate that the image quality from 24 channels sensor is much better than the 12 channels system.

Trickle beds are widely used in industrial processes. A trickle bed is a column with gas and liquid concurrently flow downward through a packed bed. Although the structure is simple, the hydrodynamics is complex in a trickle bed, and there are several flow regimes exist. In this study, of particular interest are the trickling regime and pulsating regime. By applying ECVT to an air-water trickle bed, the liquid maldistribution in the trickling regime is observed. The pulse properties in pulsating regime are quantified. A mathematical model is derived to estimate the actual liquid velocity inside the pulsating trickle bed, and it is found that the pulsation is wave propagation. In gas-liquid separation, sometimes a passive cyclonic gas-liquid separator is favored because of its simple structure, high efficiency and low energy consumption. In this study, ECVT is applied to a passive cyclonic gas-liquid separator, and the liquid distribution and the gas core behavior are investigated. A hydrodynamic model is mathematically derived to explain the gas core behavior, and the calculated results match the ECVT images well.

Bubble motion inside bubble columns is a very important topic. In this study, ECVT is applied to bubble columns with various distributors operating in different flow regimes. The spiral motion of the bubble plume is imaged, and the results match the data from optical fiber probe. Some other phenomena, such as flow regime transition, and the bubble acceleration inside a tapered conical shape column are also investigated. The last portion of this work considers ECVT applications in gas-solids systems. The gas jet in a fluidized bed is imaged by ECVT and MRI, and the results are compared quantitatively. As for irregular shape imaging domain, a bend shape ECVT is employed to investigate the solids distribution inside the riser exit region in a circulating fluidized bed.

By conducting this study, feasibilities of ECVT applications on multiphase flow systems
are demonstrated. In the last chapter of this dissertation, future works are recommended.

Link

17 September 2014

Aining WangQussai MarashdehLiang-Shih Fan

Abstract: Electrical Capacitance Volume Tomography (ECVT) is a 3D, real-time imaging technique that is recently developed to image the multiphase flow behaviour in columns of regular or irregular geometries. In this study, the ECVT measurements are conducted to obtain phase holdups and flow structures in bubble columns of a straight-cylinder shape and a tapered-cylinder shape with porous and orifice gas distributors. The phase holdups obtained by the ECVT in a straight-cylinder bubble column with porous gas distributor are verified by other measurement techniques and correlation equations reported in the literature. The flow regimes of the bubble columns are also characterized by the ECVT. Particularly, a dynamic 3D flow structure, which is uniquely represented by the spiral motion of the bubble plumes occurring within the heterogeneous regime of the gas-liquid flow in a straight-cylinder shape bubble column with perforated distributor, is captured for the first time instantaneously over the entire flow field with the ECVT. Other flow behaviour such as the converging flow pattern of the gas bubbles in a tapered-cylinder shape bubble column is also revealed by the ECVT.

Link

11 December 2013

Qussai M. Marashdeh, Fernando L. Teixeira, Liang-Shih Fan

Abstract: Electrical capacitance volume tomography (ECVT) has shown to be an effective low-cost and high-speed imaging technique suitable for many applications, including 3-D reconstruction of multiphase flow systems. In this paper, we introduce the concept of adaptive ECVT based upon the combination of a large number of small individual sensor segments to comprise synthetic capacitance plates of different (and possibly noncontiguous) shapes while still satisfying a minimum plate area criterion set by a given SNR. The response from different segments is combined electronically in a reconfigurable fashion. The proposed adaptive concept paves the way for ECVT to be applicable in scenarios requiring higher resolution and dynamic imaging reconstruction.

Link

8 November 2014

Aining Wang, Qussai Marashdeh, Brian J. Motil, Liang-Shih Fan

Abstract: Experimental results of the air–water pulsating flows in a trickle bed column were obtained using the electrical capacitance volume tomography (ECVT) system. Detailed 3-D pulse structures in both the fully developed and the transient conditions were illustrated. Pulse frequency, pulse traveling velocity, average liquid holdup and liquid holdup inside the gas-rich and liquid-rich regions, respectively, were measured. Based on a simplified model, the linear liquid velocities inside the gas-rich and liquid-rich regions were estimated. The results revealed that the gas flow rate was the most important parameter in controlling the pulsating flow properties. Discussion on the physical nature of the pulsating flow was also given.

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December 2013

Justin M. Weber, Ky J. Layfield, Dirk T. Can Essendelft, Joseph S. Mei

Abstract: Being able to accurately predict the performance and operation of multiphase flow systems continues to be a significant challenge. In order to continue the advancement of knowledge and to develop better models, a 10 cm diameter fluidized bed of 185 μm glass beads was used along with an Electrical Capacitance Volume Tomography (ECVT) sensor and high speed pressure measurements. Three dimensional images of the gas–solid flow structure were obtained and analyzed as well as frequency information from the high speed pressure transducers. The experimental data was then compared to four computational models performed with CPFD Software’s Barracuda code exploring different techniques to handle the perforated distributor plate.

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July 2013

Justin, M. Weber, Joseph S. Mei

Abstract: Understanding the fundamentals of gas–solid fluidized beds and, in general, multiphase flows has been a significant task since the conception of gas–solid fluidization and fluid particle systems. Various measurement techniques have been applied in an attempt to better understand the fundamentals of the complex gas–solid flow structures that form in fluidized beds. This information may potentially provide a better design, scale-up, and operation of these systems as well as lead to accurate performance predictions of multiphase flow systems. Electrical Capacitance Volume Tomography (ECVT) has now reached a point of development where these multiphase flow structures can be imaged accurately and reliably in three dimensions at good resolutions and sampling rates to provide significant insight into the internal gas–solid flow structures. A 10 cm ECVT sensor was used in order to investigate the bubble behavior of a 10 cm diameter bubbling fluidized bed (BFB) of 185 micron glass beads at various fluidization velocities. Three dimensional images of gas–solid flow structures as well as time average vertical and radial solid fraction profiles are presented in this paper, and average bubble diameter and bubble frequency are discussed and compared to various correlations available in the published literature.

Link

2013

Qussai Marashdeh, 2Brian Motil, Aining Wang, and Liang-Shih Fan

Abstract:

Electrical Capacitance Volume Tomography (ECVT) is a 3D imaging technique for viewing cold flow processes. It can be applied to hot units too.

ECVT is among the few known non-invasive fluid imaging tools that can be used for Space applications (Features: low cost, suitable for different applications, fast, and safe)

Tech4Imaging LLC is a technology company acclaimed for the development and commercialization of ECVT.

Tech4Imaging has a complete system of acquisition hardware, sensors, and reconstruction software for imaging multiphase flow systems (fluidized beds, trickle beds, slurry columns, flow through porous media, etc.)

Link

February 2014

Dr. Qussai Marashdeh

Abstract: A detailed understanding of multiphase flow behavior inside a Circulating Fluidized Bed (CFB) requires a 3-D technique capable of visualizing the flow field in real-time. Electrical Capacitance Volume Tomography (ECVT) is a newly developed technique that can provide such measurements. The attractiveness of the technique is in its low profile sensors, fast imaging speed and scalability to different section sizes, low operating cost, and safety. Moreover, the flexibility of ECVT sensors enable them to be designed around virtually any geometry, rendering them suitable to be used for measurement of solid flows in exit regions of the CFB. Tech4Imaging LLC has worked under contract with the U.S. Department of Energy’s National Energy Technology Laboratory (DOE NETL) to develop an ECVT system for cold flow visualization and install it on a 12 inch ID circulating fluidized bed. The objective of this project was to help advance multi-phase flow science through implementation of an ECVT system on a cold flow model at DOE NETL. This project has responded to multi-phase community and industry needs of developing a tool that can be used to develop flow models, validate computational fluid dynamics simulations, provide detailed real-time feedback of process variables, and provide a comprehensive understating of multi-phase flow behavior. In this project, a complete ECVT system was successfully developed after considering different potential electronics and sensor designs. The system was tested at various flow conditions and with different materials, yielding real-time images of flow interaction in a gas-solid flow system. The system was installed on a 12 inch ID CFB of the US Department of Energy, Morgantown Labs. Technical and economic assessment of Scale-up and Commercialization of ECVT was also conducted. Experiments conducted with larger sensors in conditions similar to industrial settings are very promising. ECVT has also the potential to be developed for imaging multi-phase flow systems in high temperature and high pressure conditions, typical in many industrial applications.

Link

2013

Qussai M. Marashdeh, Fernando L. Teixeira, and Liang-Shih Fan

Abstract: Electrical Capacitance Volume Tomography (ECVT) has shown to be an effective low-cost and high-speed imaging technique suitable for many applications, including 3D reconstruction of multiphase flow systems. In this paper, we introduce the concept of adaptive ECVT based upon the combination of a large number of small individual sensor segments to comprise synthetic capacitance “plates” of different (and possibly noncontiguous) shapes while still satisfying a minimum plate area criterion set by a given SNR. The response from different segments is combined electronically in a reconfigurable fashion. The proposed adaptive concept paves the way for ECVT to be applicable in scenarios requiring higher resolution and dynamic imaging reconstruction.

Link

September 2012

T.C. Chandrasekera, A. Wang, D.J. Holland, Q. Marashdeh, M.Pore, F. Wang, A.J. Sederman,

Abstract: Magnetic resonance imaging (MRI) and electrical capacitance volume tomography (ECVT) have been compared for the visualisation of a jet of air issuing from a distributor provided with a single orifice and supporting a bed of poppy seeds contained in a vertical tube of 50 mm diameter. The mean diameter of the seeds was 1.2 mm: the orifice was 4 mm in diameter. MRI and ECVT images were acquired in three dimensions for flow rates of air such that, when divided by the cross-sectional area of the tube, they gave superficial velocities below that required for minimum fluidisation. The ECVT images were found to be of lower contrast (as well as resolution) than the MRI, owing to smoothing inherent to the ECVT reconstruction process. An adaptive threshold method is developed to recover the 3D structure of the jet from the ECVT results. This method describes the smoothing in the ECVT images by a point-spread function that can be objectively defined by comparison with the MRI results. Using the new adaptive threshold method, the maximum discrepancy in the measured jet length by ECVT was an overestimation by 7 mm in comparison with the MRI results. The discrepancies in the measured maximum jet widths appeared to be ca. 2 mm.

Link

13 Jully 2012

Fei WangQussai Marashdeh, Aining Wang, and Liang-Shih Fan*

Abstract: Electrical capacitance volume tomography (ECVT) is a newly developed imaging technique that can quantify three-dimensional (3D) multiphase flows in a complex, geometric flow field. In this study, the 3D phase distribution images inside a gas–solid circulating fluidized bed (CFB) are obtained using ECVT. Specifically, measurements are made at a riser section and a 90° bend-shape riser exit section of the CFB. Inside the vertical riser, a symmetric core–annulus structure with a low solids holdup in the riser center along with a high solids holdup near the riser wall is observed. The average volume solids holdup and the thickness of the annulus decrease with the superficial gas velocity. A core–annulus flow structure is formed both in the vertical and horizontal parts of the bend. The annulus structure is noncentro-symmetric in the horizontal part of the bend. The solids holdup in the annulus near the top wall area in the bend is higher than that in other locations of the annulus. At a higher superficial gas velocity in the riser, the centrifugal acceleration increases due to high solids velocity in the bend, and more solids are separated to the outside of the bend from the main stream. A “reversed-S” shape solids holdup distribution along the diagonal line is also observed. The solids holdup increases and then decreases from the outer corner to the center of the bend, which indicates that a relatively dilute region is formed near the outer corner of the bend.

Link

2011

Fei Wang, Qussai Marashdeh, and Liang-Shih Fan

Abstract: Experimental studies using electrical capacitance volume tomography (ECVT) are conducted to examine gas-solid flows in a riser and a bend of a 0.05 m (2 in) ID gas-solid circulating fluidized bed (CFB) system. The quantitative measurements using ECVT are made that illustrate a three-dimensional symmetric core-annulus structure in the riser and a non-centro-symmetric core-annulus structure in the bend. Results on the volume solids holdup distributions in the riser and in the bend at various operating conditions are also obtained.

Link

1 June 2010

Fei Wang, Zhao Yu, Qussai Marashdeh, Liang-Shih Fan

Abstract: In this paper, the real time, dynamic phenomena of the three-dimensional horizontal gas and gas/solid mixture jetting in a 0.3 m (12 in) bubbling gas–solid fluidized bed are reported. The instantaneous properties of the shape of the jets and volumetric solids holdup are qualified and quantified using the three-dimensional electrical capacitance volume tomography (ECVT) recently developed in the authors’ group. It is found that the horizontal gas jet is almost symmetric along the horizontal axis during its penetration. As the jet width expands, the total volume of the gas jet increases. A mechanistic model is also developed to account for the experimental results obtained in this study. Comparison of jet penetration length and width between the model prediction and ECVT experiment shows that both the maximum penetration length and the maximum width of the horizontal gas jet increase with the superficial gas velocity. When the horizontal gas jet coalesces with a bubble rising from the bottom distributor, it loses its symmetric shape and can easily penetrate into the bed. For the horizontal gas/solid mixture jet penetration in the bed, the tail of the jet at the nozzle shrinks and the jet loses its jet shape immediately when the jet reaches its maximum penetration length, which are different from the characteristics exhibited by the gas jet. The solids holdup in the core region of the gas/solid mixture jet is higher than that in the gas jet. The penetration length of the horizontal gas/solid mixture jet is also larger than that of the gas jet.

Link

9 March 2010

Fei Wang, Qussai Marashdeh, Liang-Shih Fan, and Warsito Warsito

Abstract: This article reports recent advances and progress in the field of electrical capacitance volume tomography (ECVT). ECVT, developed from the two-dimensional electrical capacitance tomography (ECT), is a promising non-intrusive imaging technology that can provide real-time three-dimensional images of the sensing domain. Images are reconstructed from capacitance measurements acquired by electrodes placed on the outside boundary of the testing vessel. In this article, a review of progress on capacitance sensor design and applications to multi-phase flows is presented. The sensor shape, electrode configuration, and the number of electrodes that comprise three key elements of three-dimensional capacitance sensors are illustrated. The article also highlights applications of ECVT sensors on vessels of various sizes from 1 to 60 inches with complex geometries. Case studies are used to show the capability and validity of ECVT. The studies provide qualitative and quantitative real-time three-dimensional information of the measuring domain under study. Advantages of ECVT render it a favorable tool to be utilized for industrial applications and fundamental multi-phase flow research.

Link

2010

Fei Wang, Qussai Marashdeh and Liang-Shih Fan

Abstract: A 3-D Electrical Capacitance Volume Tomography (ECVT) sensor is developed here for the measurement of gas-solid flows in a 90-dgree bend at the exit region of a CFB riser. The instantaneous 3-D flow structure and the volumetric solids holdup in the bend are quantitatively measured using ECVT. The experimental results indicated that the solids reflection and volumetric solids holdup distribution in the exit region was affected by the geometry of the bend and the operating conditions of the CFB.

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2010

Fei Wang, M.S.

Abstract: Fluidized beds provide good mass and heat transfer characteristics, temperature homogeneity, high flowability of particles, and high mixing rates between solid particles and gas. Gas-solid fluidized beds have been employed extensively in chemical, petrochemical, metallurgical, food, and pharmaceutical industries. A comprehensive understanding of the complex hydrodynamics and transport phenomena in gas-solid fluidized beds are required for successful application of these systems in industry. Moreover, much of the fundamental research reported in the literature on gas-solid fluidization properties have been performed with large gas-solid fluidized beds. Little is known about gas-solid fluidization in the mini- and micro-scale channel sizes ranging from 10-3 m to 10-2 m and 10-4 m to 10-5 m, respectively. A comprehensive study on the hydrodynamics of gas-solid fluidization and the significant wall effect in the mini- and micro-channels is needed for micro-scale reactor design.

In this study, the dynamic flow behaviors in gas-solid fluidized beds are investigated by using Electrical Capacitance Volume Tomography (ECVT). Several advanced cylindrical and bend ECVT sensors are developed for the measurements. It is found that during the process of gas jetting in a 0.3 m bubbling gas-solid fluidized bed the horizontal gas jet almost maintains its symmetry along the horizontal penetration axis. The horizontal gas jet loses its symmetric shape and can easily penetrate into the bed during the horizontal gas jet and rising bubble coalescence. The prediction from a mechanistic model established in this study and ECVT experiment show that both the maximum penetration length and width of the horizontal gas jet increase with the superficial gas velocity in the bed. For the horizontal gas/solid mixture jet, the tail of the jet at the nozzle shrinks and the jet loses its jet shape immediately when the jet reaches its maximum penetration length, which is different from those exhibited by the gas jet. The maximum penetration length of the gas/solid mixture jet is larger than that without solids in the jet stream under the same operating conditions. The time-averaged volume solids concentration in three gas-solid bubbling fluidized beds with diameters of 0.05 m, 0.1 m and 0.3 m decreases with superficial gas velocity. The time-averaged volume solids concentrations in the 0.1 m and 0.3 m beds are consistent with each other, but are higher than that in the 0.05 m bed at a given superficial gas velocity. The bubble size determined from ECVT with a threshold value of 0.3 for the solids concentration is consistent with those from the literature. In a 0.05 m ID gas-solid circulating fluidized bed, a symmetric core-annulus structure in the riser is observed. It is found that the thickness of the annulus and solids holdup in the annulus near the wall of the riser decrease with gas velocity. A core-annulus flow structure is formed both in the vertical and horizontal parts of the bend. The annulus structure is non-centro-symmetric in the horizontal part of the bend. The solids holdup in the annulus near the top wall area in the bend is higher than that in other locations of the annulus. The solids holdup at the top wall region in the bend increases with the superficial gas velocity and the solids flux.

Gas-solid fluidization in the mini- and micro-channels is examined experimentally using FCC particles in six mini- and micro-channels with sizes ranging from 700 µm to 5 mm. The data conduced from a visualization system reveal a significant increase in the minimum fluidization and bubbling velocities as well as the wall friction in the mini- and channels. The pressure overshoot in the 2 mm, 3 mm, and 5 mm channels in this study is between 30% – 70%. Additionally, the maximum stable bubble size increases with the superficial gas velocity and channel size. The round-nosed slug and the wall slug are observed in the mini- and micro-channels. The fluidization regimes in the channels are significantly different from that in large gas-solid fluidized beds as the criterion for conventional regime transition are not predictive for that in the mini- and micro-channels. Differing from fluidization in a large bed, there is regime transition instability in that particulate fluidization is observed to form in the 700 µm and 1 mm channels through the bubbling/slugging transition as the gas velocity increases beyond that for the fixed bed.

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2009

Qussai Marashdeh, B.S., M.S., Ph.D.

Abstract: Electrical Capacitance Volume tomography (ECVT) is gaining increased attention as a tool for imaging and understanding multi-phase flow systems. ECVT has the advantage of providing qualitative and quantitative information of the dynamic flow behavior of the process under investigation. ECVT non-invasive sensors are potentially a useful tool for researchers in various process industries. Validation of ECVT images using other established measurement technologies is vital to establish confidence in the reliability of ECVT technology for quantitative measurements of multi-phase flow systems.

Work in this thesis is focused on using different measurement techniques to validate ECVT imaging of similar flow systems. Specifically, Magnetic Resonance Imaging (MRI) and fiber optics probes are used here. MRI is a well established imaging tool that has the reputation of providing precise high resolution cross-sectional images. On the other hand, fiber optics probes provide local density and velocity information of multi-phase flows. The combination of both techniques to validate ECVT measurements is expected to provide an acceptable estimate of the accuracy of ECVT imaging.

In addition, comparison of different ECVT images obtained by different numbers of capacitance channels is provided in the last chapter of this thesis. This comparison is useful in estimating the extent of ECVT technology in providing high resolution images.

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January 2009

D. J. Holland,*, Q. Marashdeh, C. R. Mu¨ller, F. Wang, J. S. Dennis, L.-S. Fan, and L. F. Gladden†

Abstract: This paper reports the first quantitative comparison of magnetic resonance (MR) and electrical capacitance volume tomography (ECVT) on a 50 mm diameter gas-fluidized bed of silica-alumina catalyst support particles (dp ) 58 µm). ECVT data were acquired at a temporal resolution of 12.5 ms and a nominal spatial resolution of 2.5 mm × 2.5 mm × 4.5 mm. Snapshot MR data were acquired at a temporal resolution of 26 ms and a spatial resolution of 1.9 mm × 1.9 mm in the transverse plane and 1.9 mm × 3.8 mm in the axial plane. The particles were doped with water to produce a detectable signal with MR. The two techniques are demonstrated to produce quantitatively comparable time-averaged measurements of the voidage. The bubble frequencies measured from the snapshot images using both techniques were found to be in good agreement. However, the signal intensity inside the gas bubbles was more accurate when measured with MR, and the wake structure could be more clearly resolved using MR. This was attributed to the effect of the smoothing, or point spread function, of the ECVT measurements. An initial estimate of the smoothing in the ECVT has been performed by assuming a Gaussian point spread function.

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2008

Fei Wang, Qussai Marashdeh, W. Wasito, and Liang-Shih Fan

Abstract: The horizontal gas-solid jet penetration of a gas-solid fluidized bed is studied using electrical capacitance volume tomography (ECVT). ECVT is a non-invasive imaging technique developed by the authors and it involves providing 3D concentration maps from capacitance sensors.. The fluidized bed under investigation is of 0.3m (12 inch) ID with a 0.5m ID disengagement section and has a total height of 2.4m. A gas-solid jet side injection, with 1 inch ID, penetrates the wall of the fluidized bed in the middle of the ECVT test region. Solids in the side injection are supplied through and blown into the fluidized bed using high pressure gas. Fluid catalytic cracking catalysts (Group A) are used in this study. The superficial gas velocity from the distributor of the gas-solid fluidized bed employed ranges from 0.03 to 0.24 m/s and the gas velocity from the side jet penetration ranges from 0 to 16 m/s. In this study, we observe and analyze gas and gas-solid side injection in the bubbling regime of the fluidized bed, variation in bubble shape, formation, and coalescence.

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05 March 2007

Warsito Warsito, Qussai Marashdeh, Liang-Shih Fan

Abstract:  A dynamic volume imaging based on the principle of electrical capacitance tomography (ECT), namely, electrical capacitance volume tomography (ECVT), has been developed in this study. The technique generates, from the measured capacitance, a whole volumetric image of the region enclosed by the geometrically three-dimensional capacitance sensor. This development enables a real-time, 3-D imaging of a moving object or a real-time volume imaging (4-D) to be realized. Moreover, it allows total interrogation of the whole volume within the domain (vessel or conduit) of an arbitrary shape or geometry. The development of the ECVT imaging technique primarily encloses the 3-D capacitance sensor design and the volume image reconstruction technique. The electrical field variation in three-dimensional space forms a basis for volume imaging through different shapes and configurations of ECT sensor electrodes. The image reconstruction scheme is established by implementing the neural-network multicriterion optimization image reconstruction (NN-MOIRT), developed earlier by the authors for the 2-D ECT. The image reconstruction technique is modified by introducing into the algorithm a 3-D sensitivity matrix to replace the 2-D sensitivity matrix in conventional 2-D ECT, and providing additional network constraints including 3-to-2-D image matching function. The additional constraints further enhance the accuracy of the image reconstruction algorithm. The technique has been successfully verified over actual objects in the experimental conditions.

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12 February 2007

Qussai Marashdeh, Warsito Warsito, Liang-Shih Fan, and Fernando L. Teixeira

Abstract: A new noninvasive system for multimodal electrical tomography based on electrical capacitance tomography (ECT) sensor hardware is proposed. Quasistatic electromagnetic fields are produced by ECT sensors and used for interrogating the sensing domain. The new system is noninvasive and based on capacitance measurements for permittivity and power balance measurements for conductivity (impedance) imaging. A dual sensitivity map of perturbations in permittivity and conductivity is constructed. The measured data along with the sensitivity matrix are used for the actual image reconstruction. The new multimodal tomography system has the advantage of using already established reconstruction techniques, and the potential for combination with new reconstruction techniques by taking advantage of combined conductivity/permittivity data. Moreover, it does not require direct contact between the sensor and the region of interest. The system performance has been tested on representative data, producing good results

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2006

Q. Marashdeh, A.-H. A. Park, L.-S. Fan, and F. L. Teixeira

Abstract: The applicability of different electrical tomography sensors depends on the interrogating signal as well as the sensor itself. In all electrical tomography sensors, the electrical field distribution plays a major role on the measured boundary electrical property. The electrical field distribution is based on the electrical property distribution inside the imaging domain. In this study, the electrical capacitance tomography sensor is used to study the effect of conductivity value on the field distribution. Keywords: Conductive, Electrical capacitance sensor; Multiphase flow; Particle;

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2 April 2006

Qussai Marashdeh, Warsito Warsito, Liang-Shih Fan, and Fernando L. Teixeira

Abstract: A new technique for solving the forward problem in electrical capacitance tomography sensor systems is introduced. The new technique is based on training a feed-forward neural network (NN) to predict capacitance data from permittivity distributions. The capacitance data used in training and testing the NN is obtained from preprocessed and filtered experimental measurements. The new technique has shown better results when compared to the commonly used linear forward projection (LFP) while maintaining fast prediction speed. The new technique has also been integrated into a modified iterative linear back projection (Landweber) reconstruction algorithm. Reconstruction results are found to be in favor of the NN forward solver when compared to the widely used Landweber reconstruction technique with LFP forward solver.

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10 July 2006

Q MarashdehW WarsitoL-S Fan, and F L Teixeira

Abstract: A combined multilayer feed-forward neural network (MLFF-NN) and analogue Hopfield network is developed for nonlinear image reconstruction of electrical capacitance tomography (ECT). The (nonlinear) forward problem in ECT is solved using the MLFF-NN trained with a set of capacitance data from measurements based on a back-propagation training algorithm with regularization. The inverse problem is solved using an analogue Hopfield network based on a neural-network multi-criteria optimization image reconstruction technique (HN-MOIRT). The nonlinear image reconstruction based on this combined MLFF-NN + HN-MOIRT approach is tested on measured capacitance data not used in training to reconstruct the permittivity distribution. The performance of the technique is compared against commonly used linear Landweber and semi-linear image reconstruction techniques, showing superiority in terms of both stability and quality of reconstructed images.

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Qussai Marashdeh, B.S., M.S.

Abstract: Electrical tomography techniques for process imaging are very prominent for industrial applications due to their low cost, safety, high capture speed, and suitability for different vessel sizes. Among electrical tomography techniques, electrical capacitance tomography has been the subject of extensive recent research due to its noninvasive nature and capability of differentiating between different phases based on permittivity distribution. Research in electrical capacitance tomography is inherently interdisciplinary, and areas of research in it can be categorized as: (1) sensor design, (2) hardware electronics, (3) and image reconstruction. Work presented in this dissertation includes developments in image reconstruction and sensor design.

Work on image reconstruction presented in this dissertation include developments of both forward and inverse solutions. A feed forward neural network based forward solver has been developed for fast and relatively accurate forward solutions. The forward solver has been integrated into a Hopfield optimization reconstruction technique to provide a fully non-linear image reconstruction process. In addition, a 3D volume image reconstruction has been developed by extending the 2D neural network multi objective image reconstruction technique (NN-MOIRT) to 3D applications, and inclusion of new objective functions tailored for 3D imaging.

Developments on sensor related topics provided in this dissertation are 3D capacitance sensor designs for 3D imaging and non-invasive capacitance sensors for simultaneous permittivity/conductivity imaging. In the former case, a 3D sensor with axial variation in field distribution has been used for volume imaging based on the developed Hopfield 3D optimization image reconstruction. In the latter case, an extension of the conventional capacitance sensor based on capacitance and power measurements has been provided for simultaneous imaging of permittivity and conductivity distributions.

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