40-T混合磁体外超导线圈迫流氦流动摩擦因子分析

发布时间：2018-07-07 14:31

本文选题：摩擦因子 + 流动压降　；参考：《中国科学技术大学》2017年硕士论文

【摘要】：强磁场的应用领域非常广泛,在材料科学、生物工程与医疗以及各种工业和农业应用方面均能发挥重要作用,强磁场实验装置能为这些领域的探索研究提供必要的实验环境。40-T混合磁体项目是由国家发改委资助、由中国科学院强磁场科学中心承担建设的国家大科学实验装置"稳态强磁场实验装置"的主要建设内容之一。该试验装置于2016年年底在32mm室温孔径中获得40-T稳态磁场,它由外超导磁体和内水冷磁体组成,其中外超导磁体线圈由Nb3Sn管内电缆导体(CICC)绕制而成,采用4.5K超临界氦对26条线圈通道进行迫流冷却。CICC导体由多股超导股线和铜线经过多级扭绞然后包套于不锈钢铠甲内而成,属于内冷导体。超临界氦在CICC导体内部流动,受到摩擦阻力作用产生压降和热耗散,同时带走导体在励磁过程中产生的热量。CICC摩擦因子的测量与分析是优化磁体线圈冷却策略、提高磁体运行性能的有效途径。本文旨在通过分析超临界氦在40-T混合磁体外超导磁体各线圈的摩擦因子,以优化磁体低温冷却回路和热力学工况,从而提高40-T混合磁体外超导磁体的低温稳定性,为该装置达到更高的磁场提供保障。Katheder经验公式被广泛地用于CICC摩擦因子的计算,但由于40-T混合磁体线圈各支路的CICC导体结构独特,若采用该公式来计算40-T混合磁体外超导磁体线圈内的流动摩擦因子,会存在较大误差,因此,需要修正Katheder经验公式来辅助该装置线圈内的流动状态和压降等方面的分析和研究。本文通过采用氦流体进行建模分析的方法对磁体运行数据进行分析处理,同时应用机器学习算法中的局部加权线性回归算法,排除了大量的异常点,修正了因雷诺数分布不均造成的拟合结果偏差。本文通过分析计算所得到的CICC摩擦因子计算公式与实验数据具有很高的一致性,将为40-T混合磁体外超导磁体的热工水力分析、冷却回路优化和低温稳定性改善奠定基础。
[Abstract]:Strong magnetic fields are widely used and can play an important role in material science, bioengineering and medicine, as well as in various industrial and agricultural applications. The high magnetic field experimental device can provide the necessary experimental environment for the exploration and research in these fields. The. 40-T mixed magnet project is funded by the National Development and Reform Commission. One of the main contents of the steady state high magnetic field experimental device, which is constructed by the strong Magnetic Field Science Center of the Chinese Academy of Sciences. The device obtained a 40-T steady-state magnetic field in the 32mm aperture at room temperature at the end of 2016. It consists of an outer superconducting magnet and an internal water-cooled magnet, in which the outer superconducting magnet coil is wound by a cable conductor in a Nb3Sn tube. 26 coils are cooled by 4.5K supercritical helium. CICC conductors are made up of multi-strand superconducting wires and copper wires, which are wrapped in stainless steel armour after multi-strand twisted and then wrapped in stainless steel armour. The measurement and analysis of the supercritical helium flow inside the CICC conductor resulting in pressure drop and heat dissipation due to friction resistance, and the measurement and analysis of the friction factor caused by the conductor in the excitation process are the optimization of the cooling strategy of the magnet coil. An effective way to improve the performance of magnets. In this paper, the friction factors of superconducting magnets outside 40-T mixed magnets are analyzed to optimize the low temperature cooling loop and thermodynamic conditions of supercritical helium magnets, so as to improve the low temperature stability of superconducting magnets outside 40-T mixed magnets. Katheder empirical formula is widely used to calculate the friction factor of CICC, but because of the unique structure of CICC conductor in each branch of 40-T mixed magnet coil, If this formula is used to calculate the flow friction factor in the superconducting magnet coils outside 40-T mixed magnets, there will be large errors. Therefore, it is necessary to modify Katheder's empirical formula to assist the analysis and study of the flow state and pressure drop in the coil of the device. In this paper, the method of modeling and analyzing the helium fluid is used to analyze and process the operation data of the magnet. At the same time, the local weighted linear regression algorithm in the machine learning algorithm is used to eliminate a large number of outliers. The deviation of fitting result caused by uneven distribution of Reynolds number is corrected. The formula of CICC friction factor obtained by analysis and calculation is in good agreement with the experimental data, which will lay a foundation for thermohydraulic analysis of superconducting magnets outside 40-T mixed magnets, optimization of cooling circuit and improvement of low temperature stability.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O441

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