Experimental investigation of the discharge valve dynamics in an oil-free linear compressor for Joule-Thomson throttling refrigerator

•A visual and real-time test system was set up to investigate dynamics of the linear compressor discharge valve.•The principle of the valve movement characteristics on exhaust loss is discussed.•The effect of valve dynamics on the thermodynamic efficiency of the free-piston oil-free linear compressor is studied. As the core component of the linear compressor which is a research hotspot of Joule-Thomson (J-T) throttling refrigerators for space applications, the discharge valve has a significant impact on their reliability and efficiency. Therefore, studying the dynamic characteristics of the discharge valve is indispensable which contributes to improving the compressor efficiency. Based on the oil-free linear compressor independently developed by the laboratory, a visual and real-time test system was set up to investigate the dynamics of the discharge valve and the compressor performance. While varying the parameters including piston stroke, valve stiffness, and operating frequency, the movement characteristics of the discharge valve and the thermodynamic efficiency of the compressor were measured and studied. The detailed principle of the valve movement characteristics on exhaust loss is discussed in the analysis of the results. The better discharge valve thickness for the linear compressor was selected. The experimental results indicated that the thermodynamic efficiency with the valve thickness of 0.152 mm is higher than 0.102 mm and 0.203 mm. The research in this paper will provide a valuable reference to design a discharge valve with high-efficiency and positive behavior for the linear compressor.