Research On Electrical Capacitance And Electromagnetic Tomography Integrated Sensor And Its Image Reconstruction Methods

Gas-liquid-solid flows are ubiquitous in the nature and industrial processes.It is of great significance to obtain the phase distributions of gas-liquid-solid three-phase flows.However,it is usually difficult for the existing detection methods to perform online visualization of the phase distributions of all three phases in a non-invasive and non-intrusive manner.Electrical tomography(ET)has some attractive potentials in multi-phase flow detection,primarily due to its advantages of being non-intrusive,nonradioactive,simple and low cost in hardware.The individual electrical tomographic modality is generally employed to detect the two-phase flows.And,it is usually difficult to visualize the phase distributions by using only a single tomographic modality.In this paper,an Electrical Capacitance Tomography(ECT)and Electromagnetic Tomography(EMT)dual-modality imaging method has been presented to investigate the phase distributions of gas-liquid-solid flows.The research works are presented as follows:(1)An integrated ECT and EMT dual-modality sensor has been designed and implemented for the detection and visualization of gas-liquid-solid flows.The distribution of high permeability/conductivity solid phase can be detected by EMT,while the gas phase can be identified from liquid and solid phases by investigating the differences in the electric permittivity by using ECT.The sensor can be implemented on the same cross-section of vessel/pipe.ECT electrodes are placed on the inner side,and EMT coils on the outer side.The dual modality measurements can be made in a manner of time-division-multiplexing or frequency-division-multiplexing to avoid the mutual interferences.Numerical simulation and experiments verify the feasibility of the integrated sensor in measuring gas-liquid-solid three-phase flows.(2)A multi-channel impedance measurement system based on LCR meter autobalancing bridge circuit has been designed and implemented to achieve the ECT and EMT dual-modality measurements.The system has the advantages of high precision,high stability and sweeping frequency impedance measurement.With the specially designed analog switch arrays,the number of measurement channels of LCR meter has been expanded,guaranteeing the experimental measurements of ECT and EMT.(3)To fulfill an automatic tool for ECT and EMT measurements,a tomographic software,namely TJUET,has been implemented to automate the data acquisition and image reconstruction tasks.The measurement sequences are stored in Excel sheets and can be changed conveniently.The TJUET software reads the Excel file and sends the command to Arduino Nano MCU,which operates the analog switch arrays in a prepared sequence.All the inter-channel impedances can be collected by the LCR meter,and sent to TJUET software.Thereafter,the data post-processing and image reconstruction can be performed by the TJUET software.(4)In addition,the dual-modality image fusion method based on two primary colours has been studied.By employing pixel-level image fusion,the phase distributions of all three phases could be depicted in an unified image.