G-M制冷机直接冷却的小型超导磁体系统热分析

发布时间：2018-06-13 00:39

本文选题：小型超导磁体系统 + G-M制冷机　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：制冷机直接冷却型超导磁体因其结构简单、部件紧凑以及无需使用液氦等优点,在强磁场应用领域得到广泛应用。目前,G-M制冷机是用于冷却小型超导磁体的主要制冷机类型之一。由于其自身内部运行过程复杂,有诸多不可控因素,制冷机与磁体系统耦合后的温度确定是当前较难解决的问题。对于G-M制冷机的不同型号,偏重于采用较大的漏热估算值判断制冷机是否具有足够的制冷量冷却磁体,但该方法无法对一二级冷头的稳定温度和磁体系统温度场进行准确预测,同时容易造成制冷机型号选择不当。为提高一二级冷头和超导磁体系统耦合温度场的预测精度,本文以RSDK-408D2型制冷机和10TNb3Sn超导磁体系统为例,通过制冷机冷却特性曲线拟合和Workbench热力耦合模块仿真,提出了一种可较为精确地预测G-M制冷机与超导磁体耦合后系统温度分布的方法。制冷机冷却特性曲线是根据热平衡原理进行实验得出的制冷机性能曲线,包含一二级冷头温度与冷量输出之间的重要关系。本文从热力学角度对G-M制冷机的理论制冷量进行分析,考虑各种损失,推出冷却特性曲线的函数形式,并采用1Stopt软件进行特性曲线拟合,给出了一二级冷头运行温度与制冷量的函数关系。采用10T Nb3Sn超导磁体结构进行系统的漏热计算。区别于传统算法,将一二级冷头温度T1、T2设为未知量代入各级漏热方程与冷却特性曲线方程进行求解,计算得到了制冷机两级冷头的温度,并以此作为数值模拟的初始边界条件。对二元电流引线进行了结构优化,并模拟了不同电流下电流引线的温度分布。基于ANSYS APDL磁场分析结果建立系统模型,采用Workbench稳态热分析模块将计算得到的一二级冷头温度作为边界条件进行数值模拟。经迭代模拟后得到的结果与制冷机冷却特性曲线吻合,由此得到磁体系统最终温度分布,验证了制冷机稳态条件下的冷却能力。仿真分析了RSDK-408D2制冷机布置方式下辐射屏、真空罩及HTS电流引线由热应力引起的变形情况。采用C语言编写程序,计算励磁过程中磁场的变化对磁体系统温度的影响。通过运行结果中磁体温度随时间的变化情况确定最佳励磁速度,以检验所选制冷机在动态变化的励磁过程中是否具有足够的冷却能力。
[Abstract]:Direct cooling superconducting magnets are widely used in the field of high magnetic field due to their simple structure compact components and no need to use liquid helium. At present, G-M refrigerator is one of the main types of cooling superconducting magnets. Because of its complex internal operation process and many uncontrollable factors, it is difficult to solve the problem of determining the temperature of the refrigerator coupled with the magnet system. For different models of G-M refrigerator, it is more important to use large leakage heat estimation value to judge whether the refrigerator has enough cooling magnet, but this method can not accurately predict the stable temperature of the first and second stage cooling head and the temperature field of the magnet system. At the same time, it is easy to cause improper type selection of refrigerators. In order to improve the prediction accuracy of the coupling temperature field between the first and second stage cold head and superconducting magnet system, this paper takes the RSDK-408D2 refrigerator and 10TNb3Sn superconducting magnet system as examples, and simulates the cooling characteristic curve fitting of the refrigerator and the Workbench thermal coupling module. A method for predicting the temperature distribution of G-M refrigerators coupled with superconducting magnets is presented. The cooling characteristic curve of the refrigerator is an experimental one based on the principle of heat balance, which includes the important relationship between the temperature of the first and second stage cooling head and the output of the cooling volume. In this paper, the theoretical refrigerating capacity of G-M refrigerator is analyzed from the viewpoint of thermodynamics, considering various losses, the functional form of the cooling characteristic curve is deduced, and the characteristic curve is fitted by 1Stopt software. The functional relationship between the operating temperature of the first and second stage cooling head and the refrigerating capacity is given. A 10 T NB 3SN superconducting magnet structure is used to calculate the heat leakage of the system. Different from the traditional algorithm, the temperature T _ 1 / T _ 2 of the first and second stage cooling head is set up as an unknown quantity to be solved by the heat leakage equation of all levels and the cooling characteristic curve equation. The temperature of the two stage cooling head of the refrigerator is calculated and used as the initial boundary condition of the numerical simulation. The structure of binary current leads is optimized and the temperature distribution of current leads under different currents is simulated. Based on the results of ANSYS APDL magnetic field analysis, the system model is established, and the temperature of the first and second stage cold head is numerically simulated by using the Workbench steady state thermal analysis module as the boundary condition. The results obtained by iterative simulation are in agreement with the cooling characteristic curve of the refrigerator, and the final temperature distribution of the magnet system is obtained, which verifies the cooling capacity of the refrigerator under steady state conditions. The thermal stress induced deformation of the radiating screen, vacuum hood and HTS current lead under the arrangement of RSDK-408D2 refrigerator is simulated and analyzed. The influence of the magnetic field change on the temperature of the magnet system is calculated by using C language. The optimum excitation speed is determined by changing the temperature of the magnet with time in order to check whether the refrigerator has enough cooling ability in the dynamic excitation process.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB651

【相似文献】