| Tokamak is a circular vessel that uses magnetic constraints to achieve controlled nuclear fusion.The low-temperature superconducting magnets inside the container confine and control the high-temperature plasma by generating a strong magnetic field.The thermal shield is located between the high-temperature components of the tokamak device and the low-temperature superconducting magnet system,and its main function is to provide a lightimpermeable heat shield between the high-temperature components and the low-temperature superconducting magnet system.The heat transfer area of the traditional tube-and-plate shield structure is small because the heat transfer area is only part of the contact between the cooling pipe and the shield panel,which limits the improvement of the heat transfer performance.In this thesis,the expansion plate structure is applied to the tokamak device to replace the traditional tubular and plate insulation structure.This article is mainly based on the following studies:The first step was the general design of the expansion plate thermal shield,which is a sandwich space structure that forms a cooling medium flow between the thermal shield panels.According to the mainframe model of a tokamak device and related parameters,the structure of expansion plate,shield panels and insulation accessories are designed.For the design of the expansion plate structure,molded-welding is selected as the molding method,and the optimal welding joint parameters and shield parameters are determined;for the design of the thermal shield panel,the specific dimensions of the thermal shield panel and the blocking strategy are determined;for the design of the thermal shield attachment,the design of the attachment parts such as the flap structure,the labyrinth structure,and the support structure are carried out.The thermal hydraulic performance of the expansion plate type thermal shield is studied for the heat shielding problem.The heat load of the heat shield is calculated according to the principle of radiation heat,80 K helium is selected as coolant,the inlet and outlet of each heat shield is determined,the heat shield is analyzed by applying the fluid simulation software CFX,and the flow path of the coolant inside the expansion plate sandwich was optimized according to the heat analysis results by using spoiler arrangement.In addition,the modeling and thermal analysis of tube-plate-thermal shield structure of the tokamak device are carried out,and the thermal analysis results of tube-and-plate thermal shield are compared with those of the optimized expansion plate type thermal shield;the pressure drop statistics of the final thermal shield are carried out,and the piping design was carried out under the condition that the pressure drop met the requirements.The final analysis results show that the temperature distribution of the expansion plate thermal shield panel is uniform and significantly lower than that of the tube-and-plate thermal shield,and the pressure drop meets the design requirements,which theoretically proves the superior heat transfer performance of the expansion plate thermal shield.Structural analysis was conducted for the strength of the expansion plate thermal shield under cooling to 80 K and sudden change load,mainly to verify whether the thermal shield meets the requirements under cooling from room temperature to working temperature and seismic load.Select 304 LN stainless steel as the thermal shield panel material,determine the stress assessment basis,adjust certain support positions after the analysis work including self-weight,self-weight-cooling(80K),self-weight-earthquake three types of design conditions,the results show that the maximum stress are to meet the requirements;and the space reserved for the vacuum chamber D-type area of the thermal shield for the preliminary assessment of clearance and displacement,the results show that all parts of the clearance The results show that the clearance of each part meets the requirements. |
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