Effect of gas flow rate on the gas-lubricated piston in a stirling cryocooler.

Using gas-lubricated pistons in Stirling cryocooler can reduce wear between the piston and cylinder, enhancing equipment reliability. This paper proposes a locally porous media-type gas-lubricated piston and investigates the regulatory effects of porous media structural parameters, supply pressure, and gas film thickness on the piston's static performance (flow rate and gas film load capacity).Aims to further improve the cooling performance of the Stirling cooler by optimizing the static characteristics of the piston.The results indicate that as the diameter of the porous media increases (2-5 mm), both the bearing capacity and the gas consumption curves continuously increase. Under the same diameter, a structure with a larger length-to-diameter ratio can reduce flow resistance losses and achieve greater bearing capacity. The gas supply pressure (0.2 MPa-0.6 MPa) shows a linear positive correlation with the static performance of the piston. The gas film thickness of 10-20 μm is the optimal range for energy efficiency, balancing both bearing capacity and processing feasibility. The experiment set up a piston control group (with piston flow rates of 6.78 × 10- 6m3/s, 1.02 × 10- 5m3/s, and 2.14 × 10- 5m3/s, respectively), and by monitoring the cooling performance of the same Stirling cryocooler, a quantitative mapping relationship between piston flow rate and the cooling performance of Stirling cryocooler was established. The results show that the cooling rate of Stirling cryocooler with a piston flow of 6.78 × 10- 6m3/s is significantly improved compared to the one of 2.14 × 10- 5m3/s. At 20 W@-152.6℃, the COP is 0.1; at 86 W@-88.0℃, the COP is 0.43, which is better than the cooling performance of the other two experimental groups. Therefore, it is considered feasible to optimize the efficiency of Stirling cryocooler by regulating the piston flow, providing a technical reference for the structural optimization and performance improvement of the Stirling cryocooler.