30 K脉管预冷CFD仿真研究

针对一台U型一级斯特林二级脉管混合制冷机，分析了一级冷量对二级脉管预冷对制冷机整机性能的影响。制冷机一级制冷温度为80 K，二级制冷温度为30 K，通过将一级冷指和脉管热桥连接，利用一级提供的冷量对脉管进行了预冷。通过计算流体力学(Computer Fluid Dynamics, CFD)仿真研究了脉管预冷对脉管内部温度场和速度场的影响。研究发现，对脉管进行预冷会改变脉管工作时的内部温度分布，对二级制冷能力有巨大影响。在不采用一级冷量对脉管中段进行预冷时，制冷机以二级0.7W@30 K和一级7W@80 K同时进行冷量输出，压缩机输入PV功为133 W；通过热桥将一级冷端换热器与二级脉管中段连接后，保持输入PV功为133 W，输出冷量变为二级1.2W@30K和一级6W@80K同时进行冷量输出。研究发现，U型一级斯特林二级脉管混合制冷机采用中段脉管预冷可大大提高二级的制冷能力。

CFD Simulation Study of Precooling of a Pulse Tube at 30 K

Aiming at the precooling of the pulse tube of a U-type hybrid cryocooler with a one-stage Stirling and a two-stage pulse tube, the influence factors on the cryocooler are studied. When the cooling temperature of the second stage is 30 K, the first stage cold finger is connected to the pulse tube via a heat bridge and the cooling capacity provided by the first stage is used to precool the pulse tube. The influence of pulse tube precooling on the temperature field and velocity field in the pulse tube is studied by a Fluent software. It is found that precooling may change the internal temperature distribution of the pulse tube and has a great influence on the cooling capacity of the second stage. Without the precooling of the pulse tube by the cooling capacity provided by the first stage, the cryocooler outputs its cooling capacity with its second stage of 0.7 W@30 K and its first stage of 7 W@80 K at the same time and the input PV power of the compressor is 133 W. After the first stage cold heat exchanger is connected to the middle part of the second stage vessel via a heat bridge, the input PV power of 133 W is maintained and the output cooling capacity of the second stage and that of the first stage are changed to 1.2 W@ 30 K and 6 W@ 80 K respectively at the same time. It is found that the precooling of the middle section of the pulse tube can greatly improve the two-stage cooling capacity of the U-type hybrid cryocooler.