Study on a flexible rod-type valved linear compressor without piston offset

Abstract

Over the past few decades, research has been increasing on valved linear compressors in cryogenics and refrigeration. To guarantee the high performance of the compressor, the piston needs to move at the designed maximum stroke. However, most of the compressors suffer from piston offset. Due to the reduction of stroke, the piston offset greatly deteriorates the compressor's performance. To solve this problem, a valved linear compressor with a flexible rod connecting dual pistons is proposed to eliminate the offset. The flexible rod is characterized by large axial stiffness and small radial stiffness. The large axial stiffness ensures that the two pistons move simultaneously. It counteracts the average differential pressure force on the dual pistons. The small radial stiffness allows frictionless movement of the dual pistons in the dual cylinders with slight non-coaxial deformation. A prototype was designed numerically and verified experimentally. In a none-flexible-rod compressor, the piston stroke can only travel up to 60% of its design value because of the offset. On the contrary, the flexible rod-type compressor can perform without piston offset.