| An increasing amount of energy is demanded with the development of the society recent years. Nuclear energy, which is clean, economical and sustainable, is a better choice for social development, while the shortage of uranium resource and the safety of nuclear wastes disposing are the main subjects that need to be focused on.Sodium-cooled fast reactor, which can solves these problems, is a kind of miniature nuclear reactor has been built. More and more countries including China have concerned over it. The coolant monitoring is very important for reactor’s running safety. Therefore, with the development of sodium-cooled fast reactor technology, precision detection of the coolant flow rate has become a hot research point. Whereas the coolant used in sodium-cooled fast reactor is metal Na(or NaK-78) in liquid, which is non-transparent, high temperature. Furthermore, it can have chemistry reaction with air easily. It is very difficult to measure the flow velocity of liquid Na or NaK-78, since ordinary reactor core instrument could not work in such tough situation.The non-insulation pipe wall electromagnetic flow meter(EMFM) used as reactor core instrument in sodium-cooled fast reactor coolant not only has the advantages of the typical insulation pipe wall EMFM but also solves the deficiency of the sensor structure. However, there are few theory researches on non-insulation pipe wall EMFM.Since the previous theoretical analysis method is simple and easy, the theory system is incomplete, and for its better use in the field of nuclear engineering, some key issues about non-insulation pipe wall EMFM are discussed in this thesis. The main research works of this thesis are as following:1. Basic theories and approaches about non-insulation pipe wall EMFM are described. Some basic measuring equations about electrode insulation pipe wall EMFM and its boundary conditions are summarized, and the physical meaning of the weight function is stated. Some theories, which already exits, about non-insulation pipe wall EMFM are discussed, as well as its limitation.2. The approximate measurement function of non-insulation pipe wall EMFM is studied. First of all, the structure of non-insulation pipe wall EMFM and its properties are discussed, and compared with typical electrode insulation pipe wall EMFM. The output signal of non-insulation pipe wall EMFM could be obtained by converting the output electric potential of typical electrode insulation pipe wall EMFM from the macroscopic view is highlighted. And then, an equivalent circuit model of non-insulation pipe wall EMFM is put forwarded. The pipe wall and the fluid are treated as resistor from the macroscopic viewfor describing the relationship with the output signal of flow meter.3. The weight function of non-insulation pipe wall EMFM is researched. The boundary conditions of non-insulation pipe wall EMFM and typical insulation pipe wall EMFM are comparative studied form microscopic level. And the solution domain of non-insulation pipe wall EMFM, as well as increasing of the boundary condition and its complexity will bring great difficulities for analytical solving Laplace equation are highlighted. The relationship between the electrical characterristies of pipe wall and fluid, and the distribution of weight function of the non-insulation pipe wall EMFM are obtained under the background of using virtual current density method. Then, a concept of contribution weight/loss weight is proposed based on the the distribution characteristic of virtual current density of non-insulation pipe wall EMFM. The non-insulation pipe wall EMFM’s influence on the output voltage of flow meter is described from the microscopic view. In the following, the influence of the electrical characteristics of pipe wall and fluid on the uniformity of the weight function is quantitative analysised from the aspects of the numical simulation. It provides theoretical references for the design of the flow meter and its application in engineering. And it can give full play to the advantage of electromagnetic flow sensor is not sensitive to the velocity distribution.4. The measurement characteristics of non-insulation pipe wall EMFM are researched supported by the study of weight function. A model of non-insulation pipe wall EMFM is selected form the aspects of multi-physics. And then, some results are obtained by the analysis and calculation of the influence of pipe wall and electrical characteristic of fluid on the output signal of flow meter and its conversion rate. Meanwhile, analysis on asymmetry of electrode for signal output in the processing of flow meter and its method for output electrode is executed. The relationship between asymmetry of electrode for signal output and the area of the electrode, and the output signal. These results provide good foundations for the theoretical design of the flow meter and confirmatory experiments.5. The measurement technology of non-insulation pipe wall EMFM is studied. A non-insulation pipe wall EMFM was designed according to its theoretical study and the user’s technical requirements based on the experiment system in the lab. The experiment system in the lab is introduced in detail, as wall as the experiment procedures. By comparing theoretical model and the data obtained from the experiments, it proves the correctness and reliability of the reseach method proposed in this thesis. The characteristic curves with the experimental results analysis are provided based on the theoretical model of non-insulation pipe wall EMFM. These are the referential basis for its engineering application in the future. |
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