Significant Progress in Multi-stage DC Linear Compressors for Hybrid Cryocoolers Operating at 1–2 K Made by Boreas Cryogenics
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2022-12-25
The joint research team, led by Dr. Haizheng Dang, has previously achieved the lowest temperature ever publicly reported for hybrid cryocoolers operating at 1–2 K among similar models. The linear compressor is the power source and the heart of this type of hybrid cryocoolers. It is significant for the operation and performance improvement of the hybrid cryocoolers.
Fig. 1. 3D structure of the DC linear compressor.
This hybrid cryocooler requires two types of linear compressors: one is the AC linear compressor that drives the upper-stage high-frequency pulse tube cryocooler, and the other is the DC linear compressor that drives the final-stage throttle cryocooler. To achieve the 1–2 K temperature range in the final-stage throttle cryocooler, the multi-stage DC linear compressor system is required to achieve the high pressure ratio through cascaded compression.
For example, in this hybrid cryocooler, a conventional single-stage AC linear compressor typically provides a pressure ratio of around 1.15. However, after converting to a DC cycle and implementing four-stage compression, the required pressure ratio exceeds 100. And compressor units with a pressure ratio of more over 100 have always been a significant challenge in the international field of linear compressors.
Fig. 2. Independent experimental model of the four-stage DC linear compressor.
Fig. 3. Experimental setup of the four-stage DC linear compressor.
The joint team conducted in-depth analysis of the piston offset characteristics and coupling principles in the four-stage DC linear compressor and these proposed targeted solutions. These measures reduced the actual piston offset by 65.4%, decreased the suction pressure to 1.5 kPa, and increased the total pressure ratio to 102.5—the highest pressure ratio ever publicly reported for a four-stage DC linear compressor. This research provides crucial power source support for the stable operation of hybrid cryocoolers at 1–2 K. The related work has been published consecutively in International Journal of Refrigeration.
Fig. 4. Application of the four-stage DC linear compressor in the hybrid cryocooler.
Links to the articles:
Article 1: Theoretical and experimental investigations on the piston offset characteristics in a four-stage DC linear compressor unit
Article 2: Investigations on the coupling principle of the four-stage DC linear compressor unit
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