【作者】 汤洪明；

【导师】 王莉； 贾林祥；

【作者基本信息】 哈尔滨工业大学 ， 制冷与低温工程， 2006， 博士

【摘要】 随着现代粒子加速器、可控核聚变装置等大科学工程的建设,大型超导磁体在世界范围内得到了广泛应用。而超导磁体大都运行在约4.5K(-269℃)的液氦温区,这又促进了低温技术的发展。北京正负电子对撞机重大改造工程(BEPCⅡ)将新增加3种超导设备,即1对超导四极磁体(SCQ)、1个超导螺线管磁体(SSM)和1对超导加速腔(SRF)。相应的需要建设一套制冷量为1kW/4.5K的大型氦低温系统,保证超导设备的长期稳定运行。超导设备及低温系统性能的优劣将直接影响着将来对撞机运行时各项基本物理参数,甚至直接关系到整个装置改造的成败。所以在进行超导设备及低温系统设计时,要充分考虑超导设备在低温下的工作特性以及各种运行模式。本文以BEPCⅡ中关键部件SCQ、SSM超导磁体为主要研究对象,研究了超导磁体在低温下的稳态与非稳态工作特性中的若干问题,包括冷却介质的流动特性、传热机理,磁体的冷却结构、电磁与机械性能等。目的是为超导磁体在低温下安全可靠的工作提供设计保障和理论依据。本文首先用计算流体力学软件FLUENT数值模拟SCQ磁体低温恒温器的温度分布情况,得到该磁体的热负荷,计算结果得到美国BNL国家实验室提供数据的验证。同时,还对磁体轴向和径向支撑计算了变物性下的漏热情况。模拟了SCQ磁体冷屏上的温度分布,提出8管冷却方案来取代原设计中4管冷却方案。模拟冷却氦流在SCQ磁体通道中的流动情况,比较了超临界氦流和过冷氦流这两种冷却方式对流道中热点温度的影响,为该磁体冷却方式的确定提供了依据。应用有限元软件ANSYS数值模拟SSM磁体的支撑漏热情况,并用FLUENT模拟了SSM磁体和冷屏上温度分布,为冷却管线选择合理的布置方式。应用ANSYS模拟了SCQ磁体中的反螺线管线圈在SSM磁体中的受力情况,计算的磁场力得到美国BNL实验室计算结果以及中科院高能所(IHEP)采用OPERA-2D程序计算结果的验证。在得到磁场力同时,得出了此时磁力线的分布。SCQ、SSM磁体在降温和升温过程中,进出磁体的氦流温度、压力值是随时间非线性变化的,数值模拟时单独考虑磁体较难确定边界条件。针对这一情况,本文采用将磁体和低温系统综合考虑的思路,同时考虑低温系统中传输管线、流量计和低温调节阀门的压降作用,此时磁体和低温系统互为更多还原

【Abstract】 The large-scale superconducting magnets are presently widely used in modern high-energy particle accelerators and nuclear fusion experimental device, which generally operate at liquid helium temperature region. Cryogenic technology is developing with the requirement of operation for superconducting magnets. In order to realize the goal of two orders of magnitude higher luminosity in Beijing Electron-Positron Collider Upgrade(BEPCⅡ), three type of SC devices are to be applied, including a pair of superconducting radio frequency cavities(SRF), a pair of superconducting quadrupole magnets(SCQ) and a superconducting solenoid magnet(SSM). The performance of SC device and their cooling systems has great effects on the operation of BEPCⅡ, which should be fully studied at the design stage. The cryogenic performance of SCQ and SSM superconducting magnets are investigated both at steady operation state and at unsteady state in detail, including flow and heat transfer characteristics of cooling medium, and electromagnetic, mechanical characteristics of magnets. The results are helpful for the long-term stable operation of magnets in BEPCⅡ.Above of all, the temperature distribution along the SCQ magnets has been numerically simulated by computational flow dynamic software FLUENT. The heat loads from radial and axial supports were simulated considering variable physical properties of materials. The results are in good agreement with those by BNL. The temperature distribution of heat shields was simulated and the eight tubes cooling scheme was presented to replace the four tubes cooling scheme. The fluid flow along the cooling passage of SCQ magnets were compared for both supercritical helium cooling and subcooled liquid cooling. Based on the analyses, the supercritical helium cooling scheme was suggested.The heat loads from supports for SSM magnet were numerically simulated by finite element software ANSYS and the temperature distributions on the magnet and the LN2 heat shields were studied by FLUENT. The layout of cooling pipe was determined according to the above results. The magnetic force produced by SSM magnet on the anti-solenoid of SCQ magnet was calculated, which is in good agreement with that by BNL and IHEP. The magnetic flux was更多还原