大型聚变装置低温泵测试平台的初步设计

Preliminary design of test platform for large-scale fusion reactor cryopump

大型聚变装置是一种利用磁约束来实现受控核聚变的超导托卡马克实验装置。低温泵是大型聚变装置的关键部件之一,主要用于吸附等离子体燃烧产生的氢及其同位素、氦灰等杂质气体,为等离子体燃烧提供洁净的真空环境,以及用于聚变燃料的再生。通过对大型聚变装置低温泵的结构及运行环境进行分析,提出一套低温泵测试平台设计方案用于泵的结构性能测试。测试平台主要包括缩小尺寸的试验低温泵、用于模拟偏滤器管道环境的测试容器、提供所需冷剂的低温供应系统。通过计算试验低温泵的抽速及热负荷,得出测试平台的4 K超临界氦系统的制冷量应不小于100 W,超临界氦的质量流量应不小于64 g/s;80 K液氮系统的制冷量应不小于500 W,液氮的质量流量应不小于2 g/s。低温冷凝板的表面温度直接影响到泵的抽气性能,通过有限元方法对温度条件要求十分苛刻的低温冷凝板的温度场进行分析,得出低温冷凝板表面的温度分布均匀,平均温度约为4.358 K;低温冷凝板出口处的冷却介质的平均温度约为4.357 K。根据分析结果,测试平台的低温供应系统满足设计要求,能够为试验泵的正常运行提供保障。

The large-scale fusion device is an experimental superconducting Tokamak magnetic fusion energy reactor to achieve controllable nuclear fusion.Torus cryopump is one of the key components of the large-scale fusion device. It is mainly used for adsorbing hydrogen and its isotopes, helium ash and other impurity gases produced by plasma burning, providing a clean vacuum environment for plasma combustion and regenerating fusion fuel. In this paper, through the analysis of the structure and operating environment of the cryopump of the large-scale fusion device, a design scheme of the cryopump test platform was proposed for the structural performance test of the pump. The test platform mainly consists of a reduced scale model pump, a test vessel for simulating conditions on the divertor duct and a cryogenic supply system to provide the required coolant. By calculating the pumping speed and thermal load of the model pump, the cooling capacity of the 4 K supercritical helium system on the test platform should not be less than 100 W, the mass flow rate of supercritical helium should not be less than 64 g/s, and that of the 80 K liquid nitrogen system should not be less than 500 W, the mass flow rate of liquid nitrogen should not be less than 2 g/s. The surface temperature of cryopanels directly affects the pumping performance of the pump. The temperature field of the cryopanel with very strict temperature conditions was studied by the finite element method. It is concluded that the temperature distribution on the surface of the cryopanel is uniform, and the average temperature is about 4.357 K. The average temperature of the coolant at the outlet of the cryopanel is about 4.358 K. According to the analysis results, the cryogenic supply system of the test platform meets the design requirements and guarantee the normal operation of the pump.