Three Dimensional Dynamic Imaging Of Thermal Parameters Based On The Mechanism Of Electrical CT

Monitoring the process of fossil energy extraction such as coal, oil, by effective detection techniques can improve the use efficiency and conversion efficiency, which can also reduce energy crisis. Some scholars have studied techniques detecting thermal processes in round or square space. But there are few studies for annular space which is also in wild application, such as oil horizontal drilling, annular circulating fluidized bed furnace. Because of the complexity of the flow field, temperature field, concentration field and other factors in annular space, sensor is difficult to arrange and install. The detection signal in annular space is weak, so there is less related research.In this paper, the annular space application is studied. Based on the direct three-dimensional electrical capacitance tomography (ECT) principle, thermal dynamic parameters can be detected by imaging. Two-dimensional ECT technology is relatively mature, but cannot meet the information needs. And indirect and direct three-dimensional ECT technology developed gradually. Indirect technology can obtain the information between the layers by interpolation method, in which some progress have been made. Direct three-dimensional technology can obtain the information of real permittivity distribution anywhere in three-dimensional space detected. However, there are still many problems to be solved.First, a debris flow monitoring system is built based on the traditional ECT technology, and a new sensor network of measuring debris flow with the method of field measure is proposed. Different imaging algorithm is contrasted by simulation and experiment is also implemented to simulate the effects of different conditions on debris flow. The conclusion is that rainfall is the directly derived factor leading to debris flow and the greater the slope, the more chance gravel falls down. When ratio of the sand and gravel is 6:4, debris flow most likely occurs.On this basis, the direct three-dimensional ECT technology is used to design a sensor with double helix structure to detect annular space. Simulation and model are implemented on computer and the three-dimensional matrix of sensitive field is calculated too. By analysis of distribution of three-dimensional sensitive field between different electrodes, the conclusion can be drawn that sensitive field between adjacent electrodes on the same pipe showed a single peak, the opposite position on different pipes in relatively close distance shows bimodal peak and the opposite position on different pipes in relatively far distance shows four peaks with sinking. And different shapes of material are imaged in simulation.A direct three-dimensional ECT detecting multiphase flow bench is built and the hardware circuitry is also designed to improve the defects of the low noise ratio of the system. Three-dimensional image of medium with a high precision can be shown in experiment. The cross-sectional shape and position of the distribution of medium can be recognized and relevant parameters in axial direction can also detected, such as velocity and flow direction. This technology deepen the study of the multiphase flow pattern and flow characteristics and can be ported to detect combustion and other thermal processes.In this paper, the direct three-dimensional ECT technology is used to obtain three-dimensional information in radial and axial direction simultaneously. Sensor arrangement is improved by double helical structure and continuous three-dimensional image can be obtained. Field measurements can be realized in annular measured space. This paper validate the feasibility and advantages of application of this technology in the annular space and provides the basis for the subsequent related work and improvement direction.