Xueyao Wang

Dynamic reconstruction algorithm based on the split Bregman iteration for electrical capacitance tomography

Electrical capacitance tomography (ECT) is considered a promising visualization measurement technique, in which image reconstruction algorithms play an important role in real applications. In this paper, a dynamic reconstruction model, which integrates the ECT measurement information and the dynamic evolution information of the reconstruction objects, is presented. A generalized objective function, which simultaneously considers the ECT measurement information, the dynamic evolution information of the objects of interest, the temporal constraints and the spatial constraints, is proposed. An iteration scheme that integrates the beneficial advantages of the split Bregman iteration technique and the homotopy algorithm is developed for solving the proposed objective function. Numerical simulations are implemented to evaluate the feasibility and effectiveness of the proposed algorithm. For the cases simulated in this paper, the accuracy of the images reconstructed by the proposed algorithm is improved and the artifacts in the reconstructed images can be removed effectively, which indicates that the proposed algorithm is successful in solving ECT inverse problems.

Data-driven reconstruction method for electrical capacitance tomography

Abstract The appealing superiorities, including high-speed data acquisition, nonintrusive measurement, low cost, high safety and visual presentation, lead to the success of the electrical capacitance tomography (ECT) technique in the monitoring of industrial processes. High-accuracy tomographic images play a crucial role in the reliability of the ECT measurement results, which provide the powerful scientific evidences for investigating the complicated mechanisms behind the behaviors of the imaging objects (IOs). Beyond the existing numerical algorithms that are developed for the solution of the inverse problem in the ECT area, a data-driven two-stage reconstruction method is proposed to improve the reconstruction quality (RQ) in this paper. At the first stage, i.e., the learning stage, the regularized extreme learning machine (RELM) model solved by the split Bregman technique is developed to extract the mapping between the tomographic images reconstructed by the some algorithm and the true images according to a set of training samples. At the second stage, i.e., the prediction stage, a new IO is reconstructed by the same algorithm used in computing training samples, and then the imaging result is considered as an input of the trained RELM model to predict the final result. The performances of the proposed reconstruction method are compared and evaluated by the means of the numerical simulation approach using the clean and noisy capacitance data with different noise levels (NLs). Quantitative and qualitative comparison results validate the practicability and effectiveness of the proposed data-driven reconstruction method. Research findings provide a new insight for the improvement of the reconstruction accuracy and robustness in the ECT area.

Experimental Research on the Dense CFB’s Riser and the Simulation Based on the EMMS Model

The flow structure in the CFB (circulating fluidized bed) riser has been investigated. Experimental studies were performed in a cold square section unit with 270u2009mm×270u2009mm×10u2009m. Since the drag force model based on homogeneous two‐phase flow such as the Gidaspow drag model could not depict the heterogeneous structures of the gas‐solid flow, the structure‐dependent energy‐minimization multi‐scale (EMMS) model based on the heterogenerity was applied in the paper and a revised drag force model based on the EMMS model was proposed. A 2D two‐fluid model was used to simulate a bench‐scale square cross‐section riser of a cold CFB. The typical core‐annulus structure and the back‐mixing near the wall of the riser were observed and the assembly and fragmentation processes of clusters were captured. By comparing with the Gidaspow drag model, the results obtained by the revised drag model based on EMMS shows better consistency with the experimental data. The model can also depict the difference from the two exit confi...

Experiment Investigation on Concentration and Mass Flow Measurement of Pulverized Coal Using Electrical Capacitance Tomography

Accurate measurement of the concentration of pulverized coal in various pipes plays a key role in assuring safe and economic operation in a pulverized coal‐fired boiler in the process of combustion. In this paper, experimental studies are implemented on the measurement of a lean mass flow in a pneumatic conveying pipeline using electrical capacitance tomography (ECT). In this system, a cyclone separator is employed, where the sensors are placed, in order to compensate the inhomogeneity of the sensor sensitivity. The mass flow rate is determined from the solids velocity and the volumetric concentration. The former is measured by cross‐correlating the capacitance fluctuations caused by the conveyed solids, and the latter by an image reconstruction method, and then this two parameters are combined to give the solids mass flow rate. The distribution of void fraction in radial direction, the average void fraction and the wavy characteristics are analyzed. The feasibility and reliability of the method are verif...