A Novel Oil-free Dual Piston Compressor Driven by a Moving Coil Linear Motor with Capacity Regulation Using R134a

Abstract

Improving compressor efficiency is very important to save energy and reduce greenhouse gas emissions. A novel oil-free dual piston compressor prototype driven by a moving coil linear motor was developed, and its working principle was described in detail. The prototype was integrated with a test rig to measure the operation characteristics, the compressor efficiencies and the coefficient of performance (COP). The results show that the dual piston structure results in extraordinary sinusoidal gas force and electromagnetic force and significantly reduces piston offset, which is completely different from the traditional single piston structure. Compared with the variable frequency method, the variable stroke method has lower energy consumption and a higher COP, which is more suitable to cooling capacity regulation for the prototype. The maximum COP, motor efficiency and volumetric efficiency are 5.34, 87.9% and 79.1%, respectively, under the design condition (the evaporation pressure is 0.35 MPa, and the pressure ratio is 2.54). The COP of the linear compressor is 38%, 24% and 12% higher than the commercial crank-driven reciprocating compressor at the pressure ratios of 2.54, 2.80 and 3.90, respectively, which reflects the efficiency advantage of the dual piston linear compressor in household refrigeration.