Experimental Study on Characteristics of a Valved Hydrogen Linear Compressor

Linear compressors offer the advantages of a compact structure, high reliability, and long service life, and thus possess considerable potential for space applications. To address the problem that in existing linear compressors used for hydrogen compression, the NdFeB permanent magnets are prone to damage caused by hydrogen embrittlement resulting from chemical reactions with hydrogen, a valved linear compressor specifically designed for hydrogen service is developed. The compressor employs an opposed dual-piston architecture and is driven by a moving-coil linear motor. By completely encapsulating the magnetic steel within a sealed cavity formed by the outer housing and the external magnetic pole, physical isolation between the magnets and the hydrogen is achieved, thereby structurally avoiding the risk of hydrogen embrittlement. A compressor performance test platform is established, and the effects of charge pressure （ranging from 0.25 MPa to 0.55 MPa） and input voltage （ranging from 8 V to 16.4 V） on the pressure ratio, mass flow rate, and exergy efficiency were experimentally investigated. The experimental results show that, at a suction pressure of approximately 0.1 MPa, the compressor is capable of achieving a maximum pressure ratio of 5.0, with a corresponding mass flow rate of 3.9 mg/s; the mass flow rate decreases following a quadratic function relationship with the increase of the pressure ratio, whereas the input electric power increases in an approximately linear manner with the increase of the input voltage. Based on thermodynamic analysis, an exergy efficiency contour map of the compressor is plotted, which reveals that the exergy efficiency first increases and then decreases as the pressure ratio rises. The maximum exergy efficiency achieved is 34.94%, and the optimal efficiency operating range corresponds to a suction pressure of 0.27 MPa to 0.33 MPa and a discharge pressure of 0.45 MPa to 0.51 MPa. The research outcomes obtained from this work validate the operational stability and reliability of the developed hydrogen linear compressor, and thereby provide key technical support for Joule-Thomson cryocoolers operating in the liquid hydrogen temperature range for space applications.