Investigation Of ECT Sensor With Composite Electrodes By Simulation And Experiments

Multiphase flow systems are prevalent among many industrial fields,such as oil industry,pharmaceutical industry and chemical industry etc.Real-time detection of multiphase processes is fundamental to the understanding and optimization of the processes.Electrical capacitance tomography is an effective technique used for the real-time measurement of the multiphase flows.The ECT has been widely employed in multiphase operations because of its advantages of being non-intrusive and non-invasive,robust,fast imaging speed,fast image speed and low cost.However,the technique encounters many difficulties on the path of improving the sensitivity and spatial resolution of large scale ECT sensors.The aim of the research is to explore the effective methods to improve the spatial resolution of large scale electrical capacitance tomography(ECT)sensors.Two approaches,referred to as the two-electrode excitation strategy and the large scale ECT sensor with composite electrodes,are applied to achieve the goal.The methods of investigation contain numerical simulation and static experimental investigation.In numerical simulation,the performance of three ECT sensors with different electrode structures,the ECT sensor with external electrodes(EE sensor),the ECT sensor with external-internal electrodes(IEE sensor)and the ECT sensor with composite electrodes(CE sensor),are evaluated.The research focuses on the effect of the number of external electrodes,from 8,12 to 16,on the quality of reconstructed images using different reconstructed algorithms.The algorithms used for image reconstruction in simulation research include Linear Background Project(LBP),Landweber Iteration and the Modified Landweber Iteration.The results of simulation research present that the ECT sensor with 12 external electrodes can obtain a high quality of reconstructed images.The structure of electrodes is used for the design of large scale ECT sensor employed in experimental research.In experimental research,the influence of excitation strategy and structures of ECT sensors on the performance of large scale ECT sensors is evaluated.The research on excitation strategy highlights the effects of two-electrode excitation strategy on the performance of the large scale IEE sensor designed for the research.In the research,five two-electrode excitation strategies are involved and expected to improve the sensitivity in the central region of the IEE sensor.The image quality with the five two-electrode excitation strategies is in comparison with one-electrode.The reconstructed algorithm is LBP and a modified reconstructed method based on the LBP is proposed to reduce the effect of noise.The performance of the IEE sensor with the modified LBP and the six excitation strategies is evaluated in terms of the relative error of solids concentration.In the study of structures of large scale ECT sensors,three large scale ECT sensors,the EE sensor,the IEE sensor and the CE sensor,are built and the reconstructed images of the three ECT sensors with LBP algorithm are used to evaluate the performance of the three ECT sensors.In image reconstruction,two methods of obtaining normalized capacitances are employed and the effects of the two normalized methods on the quality of reconstructed images of different sensors are investigated by solid concentration of reconstructed images.