This report demonstrates the successful development of a design method reducing oil circulation ratio (hereafter OCR) in swing compressors, based on calculations from a simplified model and an actual experiment. The developed OCR analysis tool features the addition of oil circulation flow rate circuit to the oil supply circuit that diagnoses the pump, the oil feeding passage, and the bearings by electrical circuit. The oil circulation flow rate is affected by refrigerant flow. In consideration of the complementary effects of refrigerant gas and oil circulation flow rate, including wall impingement of oil droplets, the gravity of oil droplets, and buoyancy, calculations can be conducted as separation efficiency ratio. In the experiment, the behavior of oil droplets in refrigerant in a compressor outfitted with pressure-proof glass was observed with a high-speed camera. It was thereby ascertained that the predicted speed of oil droplets and the actual speed in the compressor were almost the same. The effects of a drop in oil level during operation due to the oil circulation flow rate can be taken into account, something previously impossible with conventional circuits. The conclusive analytical precision of OCR is a range of 30–115Hz with a margin of error of ±0.3wt%. Using this method, design points that have substantial impact on OCR reduction can be clarified. With structural changes to the motor-rotor as suggested from the analysis, OCR can be reduced. Consequently, a significant reduction in the period necessary for compressor development has been achieved.

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