Research On Application Of Electrical Capacitance Tomography Technique To Micro-scale Combustion In Porous Media

Micro-combustion chamber is the most important and complicated part in the micro dynamic device. Fast development of micro dynamic device brought people's interest into micro combustion flame which is the base of researching high efficient, safe and stable micro-combustion chamber. However, the characters of micro-scale flame are not that of macro-scale flame. Nowadays, the basic research on the characters of micro-scale flame is rarely at home and abroad, and the basic characters in the micro-scale combustion process cannot be understood well.Electrical capacitance tomography (ECT) is a process tomography (PT) based on capacitance sensor. It has the advantage of being real-time, non-intrusive, non-hazardous and being capable of acquiring 2D/3D image information of process parameters. It provides an effective tool for the recognition of flow patterns and the measurement of multi-phases flow parameters. Currently, it is widely used and becoming a hot spot in PT research. However, it is rarely used in the micro-size condition.and combustion.ECT is applied to on-line visualizing detection for combustion flame of the micro-scale combustion in porous media. ECT was applied to detect flame of micro-scale combustion, which not only develop acknowledge of micro-combustion, but also extend the applications of ECT in porous media and combustion field. This work has profound theoretical and practical values with main contributions as follows:This paper introduced ECT system's structure, working principal and application range. And it highlighted the application of ECT to detect flame, a new idea that the principle of detecting flame by ECT is flame ionization effect was put forward; the reason for greater change of permittivity caused by the flame ionization effect was analyzed. The number of ionic is obtained by numerical computation based on the chemical reaction kinetic, which provide a foundation for further revealing flame ionization effect and analyzing the principle of detecting flame by ECT.A novel high temperature endurable electrical capacitance sensor was designed and made to overcome the shortcomings of ECT sensor that cannot measure flames in high-temperature. Advanced techniques such as sintering, electroplating and spot welding were applied to this novel sensor. Some advantages of this sensor were introduced and testified them by experiments. Capacity values in low level and high level respectively were analyzed, and experimental results indicate that the measured results matches well with real conditions.An experiment plat for micro-combustion visualizing measurement was built up to achieve on-line micro-scale flame measurement. It decrypted important devices of the experiment unit. Visualizing measurements in low flow (small flame) and high flow (big flame) were made respectively; the flame images (small flame and big flame) were analyzed. The instability and incompletely of micro-combustion by ECT images were demonstrated. Measuring combustion was divided into two groups: the instability combustion and the stability combustion. The flame images change more obviously when combustion is instable.The numerical computations were implemented from two aspects: the first was to use CFD to simulate premixed combustion in porous media; the second, the micro-scale combustion was analyzed and simulated from the viewpoint of the chemical dynamics. And then, the relationship between the chemical kinetic and combustion was showed. The characters of micro-combustion were described, and the incompletely combustion was also considered; the numerical simulation for the micro-combustion was achieved using CHEMKIN software; and simulation results indicated that the active matters can strengthen micro-combustion.