Experimental investigation of system orientation effects in the two-stage gas-coupled Stirling/pulse tube hybrid cryocooler.

Current deep space exploration requires an increasingly urgent demand for cryogenic environments. Hybrid cryocoolers, as a new refrigeration structure, have specific application potential, and the link between gravity and cooling performance is unclear. This research investigates the gravitational characteristics of two-stage gascoupled Stirling/pulse tube hybrid cryocoolers with high pressure ratios and narrow temperature span. 2D CFD simulations were conducted on the working fluid flow in the second-stage pulse tube. The simulation results demonstrate that higher pressure ratios and narrower temperature spans decrease gravitational effects on pulse tube performance. A ground-based rotating platform was constructed to test cryocooler performance at various angles. Experimental results reveal that, due to its unique construction, the hybrid cryocooler exhibits minimal performance variation when rotated, with no-load temperature swings within 2 K.