Experimental study of an oil-free swing vane compressor

Conventional compressors must always be operated in the upright orientation to ensure that the oil sump is always located at the lowest position to allow the collection of lubricant back to the oil sump by gravity. As a result, conventional compressors are not suitable for applications where orientation-free and portability of the system are required. Applications such as wearable cryogenic cooling bags for the ease of vaccine transportation, compact cryogenic coolers for space applications or even as a portable oxygen concentrator (POC) for ambulatory patients will not be feasible with current compressors. A direct solution would be to eliminate the need for oil lubrication in the operation of a compressor. This would require a successful development of an oil-free compressor. In this work, an oil-free swing vane compressor prototype was designed, instrumented and tested. Its performance was evaluated with air and R134a as working fluids. For experiments with air at 1080 to 1800 rev min(-1), pressure ratios of up to 4.08 with mechanical and volumetric efficiencies ranging from 22.0% to 40.0% and 30.9% to 67.5% were obtained, respectively. For experiment with R134a at 1620 rev min(-1), the prototype has achieved mechanical and volumetric efficiencies of 45.1% and 55.5%, respectively, with a coefficient of performance (COP) of 1.25. Potential failure modes of this oil-free compressor have been identified and recommendations for design improvement are also presented in this study.