超导四极磁体降温和升温过程的数值模拟
Numerical simulation on cool-down and warm-up processes of superconducting quadrupole magnet for BEPC Ⅱ
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摘要: 超导四极(SCQ)磁体是北京正负电子对撞机重大升级改造中的新增关键设备之一，在磁体降温和升温过程中，温度梯度引起的过大热应力有可能毁坏磁体。从SCQ磁体安全运行角度来研究该磁体降温和升温过程，提出了SCQ磁体降温和升温的数值模型。利用该模型计算得到降温和升温时间分别为120 min和150 min。考察了氦流进出磁体温度、压力、磁体上最高温度和最低温度以及最大温差的变化过程。降温过程中磁体上的最大温差为46.5 K，升温过程中磁体上的最大温差为47.3 K。降温过程中氦流最大压力为0.39 MPa，升温过程最大压力为0.41 MPa。为保证磁体安全运行，应小心调节混合气的温度，尽量使磁体上的温度分布均匀后再注入4.5 K或300 K的氦气。Abstract: A pair of superconducting quadrupole(SCQ) magnets are applied for Beijing Electron-Positron Collider Upgrade (BEPC Ⅱ). The magnet can be destroyed by the excess mechanical stress caused by thermal gradients during the cool-down and warm-up processes. This paper presents the cool-down and warm-up processes in terms of magnet safe operation. A mathematical model and an analytical method are developed and the time of cool-down and warm-up is calculated, which is respectively 120 minutes and 150 minutes. The transient changes of the operation parameters are obtained, including the inlet and outlet temperature and pressure of helium to cooling loop of the magnet, the highest and lowest temperature of the magnet, and the maximum temperature difference along the magnet. The peak maximum temperat
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Key words:
- bepc Ⅱ /
- superconducting quadrupole magnet /
- cool-down /
- warm-up /
- numerical simulation
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