Simulation study on electrical resistance tomography using metal wall for bubble detection

Industrial process pipelines are mostly known to be constructed from metal which is a conducting material. Bubbles or gas detection are crucial in facilitating the bubble columns performance. By employing the Electrical Resistance Tomography (ERT) technique, a simulation study using COMSOL has been conducted to investigate the effect of excitation strategy, bubble sizes and locations towards the metal wall system. As for the current excitation strategy, conducting boundary protocol has to be applied when it comes to metallic vessel to overcome the grounding effect. Bubbles with a greater size than 2 mm and especially the one that is located near the wall boundary are much easier to detect. Further potential improvements to the current design and image reconstruction of the ERT system are desirable to improve the detection of small and centred bubble

Study and design of an ultrasonic flow tomographic front-end multi level measurement system

With the rapid evolution of electro-acoustical technology, ultrasonic tomography has made considerable progress in industry. An ultrasonic tomography system provides non-invasive and non-intrusive flow visualisation that enhances the understanding of fluid flow processes. The function of ultrasonic tomography is to continuously monitor the dynamics of liquid flow without interrupting the flow. The ultrasonic tomography technique is fully supported by a front-end hardware system. The front end is defined as all the hardware circuitries, including the ultrasonic transducer up to the Analogue-to-Digital Convertors (ADCs), even though the primary focus is the analogue signal processing components. We present here the challenges and trade-offs in the implementation of a front-end system by first explaining the basic operation of such a system, and then indicating what particular performance parameters are needed to ensure optimal system operation. Based on the results from our research studies, we propose an improved front-end multi-level solution that is more accurate than previous solutions and provides real-time measurement capability

Fundamental Sensor Development in Electrical Resistance Tomography

This paper will provide a fundamental understanding of one of the most commonly used tomography, Electrical Resistance Tomography (ERT). Unlike the other tomography systems, ERT displayed conductivity distribution in the Region of Interest (ROI) and commonly associated to Sensitivity Theorem in their image reconstruction. The fundamental construction of ERT includes a sensor array spaced equally around the imaged object periphery, a Data Acquisition (DAQ), image reconstruction and display system. Four ERT data collection strategies that will be discussed are Adjacent Strategy, Opposite Strategy, Diagonal Strategy and Conducting Boundary Strategy. We will also explain briefly on some of the possible Data Acquisition System (DAQ), forward and inverse problems, different arrangements for conducting and non-conducting pipes and factors that influence sensor arrays selections

Image reconstruction of metal pipe in electrical resistance tomography

This paper demonstrates a Linear Back Projection (LBP) algorithm based on the reconstruction of conductivity distributions to identify different sizes and locations of bubble phantoms in a metal pipe. Both forward and inverse problems are discussed. Reconstructed images of the phantoms under test conditions are presented. From the results, it was justified that the sensitivity maps of the conducting boundary strategy can be applied successfully in identifying the location for the phantom of interest using LBP algorithm. Additionally, the number and spatial distribution of the bubble phantoms can be clearly distinguished at any location in the pipeline. It was also shown that the reconstructed images agree well with the bubble phantoms

Review of wire-mesh tomography in different experiments

Wire-mesh tomography is completely new to the tomography field. First founded in 1998, the wire-mesh tomography had been used in several sectors as secondary optional sensors. This sensor can be used to gain void fraction distribution in multiphase flow visualization. By using tomography techniques, several measurements like velocity or phase fraction boundaries can be determined and analysed. The sensor basically built perpendicularly as transmitter and receiver layer located above and below respectively. With wires made of tinned copper and 16 sensors for each layer, the tomography is considered low-cost, easy built and can sustain in a harsh environment to investigate multiphase flow. As an instantaneous tomography method, wire-mesh tomography has advantage in speed but has less image resolution because classic wire-mesh tomography image reconstruction methods only provide same amount of pixels as measurement number. In order to increase image resolution, a new image reconstruction method based on sensitivity map is proposed, which is of providing more pixels (sub pixels) by solving inverse problem with capacitive wire-mesh tomography image reconstruction. The image reconstruction algorithms, including the traditional wire-mesh direct image reconstruction algorithm, the linear back projection, the projected Landweber iteration, and the total variation based iteration, are conducted and the results are compared each other

Hardware Development of Dual-Modality Tomography Using Electrical Resistance and Ultrasonic Transmission Tomography for Imaging Liquid and Gas

In decades, single-modality technique focuses on particular application such as liquid/gas, gas/solid, liquid/liquid and liquid/solid which has drawbacks in imaging complex flow with multiple components. This paper focuses on the development of dual-modality tomography system (DMT) integrating ultrasonic tomography and electrical resistance tomography (ERT) to visualize cross-sectional images of two-phase liquid/gas in vertical column. A combination of soft-field and hard-field tomography system measures different physical parameters of two-phase liquid/gas specific of two different material properties which are conductivity (σ) and acoustics impedance (Z). A DMT system is developed with 16 units of ultrasonic transceiver sensors, and 16 units of ERT electrode positioned alternately on a single-plane arrangement to perform measurement simultaneously. The reconstructed tomographic images obtained from measurement data from these two modalities are then fused into a single tomographic image by employing discrete wavelet transform (DWT)

Hardware Development of Dual-Modality Tomography Using Electrical Resistance and Ultrasonic Transmission Tomography for Imaging Liquid and Gas

In decades, single-modality technique focuses on particular application such as liquid/gas, gas/solid, liquid/liquid and liquid/solid which has drawbacks in imaging complex flow with multiple components. This paper focuses on the development of dual-modality tomography system (DMT) integrating ultrasonic tomography and electrical resistance tomography (ERT) to visualize cross-sectional images of two-phase liquid/gas in vertical column. A combination of soft-field and hard-field tomography system measures different physical parameters of two-phase liquid/gas specific of two different material properties which are conductivity (σ) and acoustics impedance (Z). A DMT system is developed with 16 units of ultrasonic transceiver sensors, and 16 units of ERT electrode positioned alternately on a single-plane arrangement to perform measurement simultaneously. The reconstructed tomographic images obtained from measurement data from these two modalities are then fused into a single tomographic image by employing discrete wavelet transform (DWT)

Wire-mesh tomography sensors for multiphase flow investigations

Wire-mesh tomography is new to the tomography field. First founded in 1998, the wire-mesh tomography had been used in several sectors as secondary optional sensors. The wire-mesh sensor can be used to gain void fraction distribution in multiphase flow visualization. By using tomography techniques, several measurements like velocity or phase fraction boundaries can be determined and analysed. The sensor basically built perpendicularly as transmitter and receiver layer located above and below respectively. The sensor wires are made of copper and 16 sensors for each layer, those sensors are considered low-cost, easy built and withstand a harsh environment to investigate multiphase flow. Traditional wire-mesh tomography image reconstruction methods only supply the same number of pixels as the measurement number, therefore wire-mesh sensors have a speed benefit but a lower image resolution. The findings from the previous experiments indicate difference in capacitance and other factors on the output

Wire mesh tomography system for horizontal two-phase fluid flow investigation

Simultaneous flow of liquid and gas is commonly found in process industries, such as petroleum pipeline transport, chemical process, oil and gas pipeline transport and many more. Phase distribution monitoring and visualizing for such flow is important to ensure the operation safeness and effectiveness. This study aims to investigate wire-mesh tomography system on solid-free two-phase flow monitoring and visualization. Experiment was conducted on a horizontal liquid/gas flow with an inner diameter of 84mm. A 16 x 16 wire-mesh sensor was designed and applied in this study to obtained the raw data from the target flow. The sensor worked together with transceiver circuit and data acquisition and image reconstruction software to visualize the flow condition and void fraction. Tomogram images were resulted as the final results of this experiment

Application study on bubble detection in a metallic bubble column using electrical resistance tomography

Electrical resistance tomography (ERT) has been chosen as the field of study because of its advantages of being low cost, suitable for various kinds and sizes of pipes and vessels, having no radiation hazard, and being non-intrusive. In the development of ERT systems for metallic bubble column, prior knowledge of the fundamental process of the ERT system whilst improving the design and operation of the process equipment is essential. The fabricated electrodes need to be electrically insulated from the metal wall. Besides that, conducting boundary strategy is implemented to overcome the grounding effect of the metallic vesse