Study of optimizing the secondary cylinder size in a novel dual-piston carbon dioxide linear compressor to suppress piston offset.

Based on a previously proposed novel dual-piston two-stage carbon dioxide (CO2) linear compressor, this research aims to further inhibit the piston offset and improve overall system performance and efficiency by purposefully exploring the optimal design of the two-stage cylinder diameter. A comprehensive simulation model is developed to analyse the dynamic characteristics and performance implications associated with varying cylinder diameters in the two-stage configuration. The study explores the influence of cylinder diameter on gas forces, piston offset, and compression process leakage. The results show that through the optimized design of the two-stage cylinder diameter, the piston offset can be reduced by >50 % and the relative leakage loss can be reduced by 2.22 %. Under 12 MPa discharge pressure, a relative efficiency improvement of 5.27 % can be
achieved. The optimal compressor efficiency is achieved between intermediate pressure index 4 and 5. This result provides valuable guidance for the design of the second-stage piston. Finally, a prototype was developed according to the design principle, and its piston offset suppression effect was validated experimentally. Under a pressure difference close to 0.7 MPa, the piston offset consistently remained below 0.2 mm.