Experimental investigation on helium valved linear compressors with different active offsets

Abstract

Piston offset in the helium valved linear compressor (VLC) deteriorates the cooling performance and operating life of Joule-Thomson (JT) refrigerators, especially in aerospace applications. To clarify the influence of piston offset on the VLC performance, an experimental investigation was carried out. Based on a laboratory developed VLC, the effects of piston offset on the suction and discharge pressure, pressure ratio, mass flow rate, motor efficiency, volume efficiency and adiabatic efficiency are systematically studied under two piston motion states (fixed piston displacements and full strokes). The results show that when the piston stroke is constant, the offset will increase the discharge pressure and mass flow rate, and decrease suction pressure. When the piston moves at full stroke, the offset will reduce the discharge pressure and mass flow rate, and increase suction pressure. Regardless of the working conditions, the existence of offset will affect the efficiency of the compressor, hence increasing the power consumption.