Phase Shift Adjustment And Optimization For Miniature Pulse Tube Cryocooler

Owning to its advantages of high efficiency, compacted structure and fast cooling-down time, regenerative cryocoolers are perfect for cryogenic applications in superconducting cooling, medical surgery and space infrared observing, etc. Without any moving part in the cold end, pulse tube cryocooler has been regarded as more suitable for space utilization in terms of lower vibration, higher stability, longer life and lower electromagnetic interference (EMI) noise. In recent years high frequency Stirling type pulse tube cryocoolers have been rapidly developed, especially for ones with high cooling capacity working at liquid nitrogen temperatures.In this study theoretical and simulating analyses were first conducted on high frequency Stirling type miniature pulse tube cryocoolers with high cooling capacity. Next, a co-axial pulse tube cryocooler was designed and developed, and the phase shift was merely adjusted by inertance tubes. The phase shift mechanism was carried out on this test bench. Based on above works, a new large swept volume moving-magnet linear compressor was specially designed and built in order to meet the requirements to drive the miniature pulse tube cryocooler. The main works were summarized as following:(1) The gas phase-distribution and other thermodynamic parameters for co-axial pulse tube cryocoolers with high cooling capacity were theoretically and simulatively analyzed. Based on previous literatures and initial design on the gas displacement and pressure fluctuations of the system, the theoretical cooling capacity and different kind of losses were calculated.(2) A co-axial miniature pulse tube cryocooler was designed, manufactured and assembled. Based on the optimization design of Stirling type pulse tube cryocoolers with high cooling capacity, the temperature distribution, pressure phase variation and overall cooling performance were tested. High accuracy, intelligentialized measurement system were adopted to ensure the accuracy and high speed of experiment data.(3) The test results of phase shift and optimization were analyzed, and the phase adjustable effects of different combination of inertance tubes were presented and explained by gas phase mechanism. It showed that the inertance tube with small inner diameter and short length worked better for this system, due to the equilibrium between the flow resistance and phase shift. After optimization, the lowest temperature of 79K was obtained, and the cooling capacity of 1.4W at 95K was achieved, with the input net power of 60.4W. The corresponding Carnot efficient was 7%.(4) A new design of high efficiency moving-magnet linear compressor with large swept volume was established in order to overcome the disadvantages of moving-coil linear compressor used in above experiments. Several original designs were achieved combing classic linear compressor designing theory and electric-magnetic field finite element simulation. The simulation results showed that the present design method was better than most exist design methods of moving-magnet linear compressor.