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研究目的:研究新型磁性回热填料Gd2O2S对液氦温区高频脉管制冷机多级回热器损失特性的影响。创新要点:确定了不同回热填料以及运行参数(频率、平均压力)下液氦温区多级脉管制冷机的制冷温度和各级预冷量,进一步明确了4 K高频回热损失机理。研究方法:采用理论研究与实验验证相结合的方法,基于一台两级G-M型低频脉管制冷机预冷的单极斯特林型高频脉管制冷机,研究多级回热器在高频以及4 K温区下的损失特性。选取新型回热填料Gd2O2S替代部分回热填料HoCu2,比较回热器采用两种填料时在不同运行频率及平均压力下的冷端制冷温度(图10)、各级预冷量和预冷温度(图11–12)。重要结论:采用孔隙率较小的新型磁性回热填料Gd2O2S可显著改善第一级回热器内压力波与质量流的相位关系,从而减小该级回热损失。减小平均压力可以降低制冷机无负荷制冷温度并减小第二级预冷量,但制冷工质氦的体积比热容会急剧增大,从而使低温级回热器的换热对频率非常敏感。此外,频率对高温级回热器的回热特性影响不明显。该方法可以为三级斯特林型4 K多级脉管制冷机提供设计依据。
Objective: To study the effect of Gd2O2S on the loss characteristics of multistage regenerators in high-frequency pulse tube refrigerator with liquid helium. Innovative Points: The cooling temperature and pre-cooling capacity of multi-stage pulse tube refrigerator with liquid helium temperature under different backfill temperature and operation parameters (frequency and average pressure) were determined, and the 4 K high-frequency heat recovery loss mechanism was further clarified . Research methods: Based on the combination of theoretical research and experimental verification, based on a two-stage monolithic Stirling-type high-frequency pulse tube refrigerator precooled with a low-frequency pulse tube refrigerator, Frequency and 4 K temperature zone loss characteristics. Select a new type of regenerative packing Gd2O2S instead of part of the regenerative packing HoCu2, compare the two types of packing when the regenerator at different operating frequencies and average pressure of the cold-side cooling temperature (Figure 10), pre-cooling at all levels and pre-cooling temperature Figure 11-12). Important Conclusions: The use of Gd2O2S, a new magnetic recuperative packing with smaller porosity, can significantly improve the phase relationship between the pressure wave and mass flow in the first stage regenerator and thus reduce the heat recovery loss at this stage. Decreasing the average pressure can reduce the refrigeration load without refrigeration and reduce the second precooling capacity. However, the volumetric specific heat capacity of the helium refrigerant increases sharply, which makes the heat transfer of the cryogenic regenerator very frequency sensitive. In addition, the frequency has no obvious effect on the heat recovery characteristics of high temperature regenerator. The method can provide design basis for three-stage Stirling 4 K multi-stage pulse tube refrigerator.