Recently, the rotation rates used in fluid machines have been increasing as such machines continue to be downsized. However, these high rotation rates lead to the possibility of lubricant oil mist formed inside the compressor becoming mixed with the refrigerant gas, which can lead to a decrease in the heat exchange efficiency. The present study attempted to clarify the separation mechanism for refrigerant gas-lubricant oil mist two-phase flow during swirl flow in order to improve the oil mist separation efficiency. Both experiments and numerical simulations were carried out to investigate the relation between the oil mist separation efficiency and the flow characteristics in a test chamber containing a rotor. It was found that the flow characteristics were determined by the swirl number Sw, and the flow pattern was quite different for Sw = 1.0, 1.5 and 3.0. In addition, the oil mist separation efficiency increased with Sw and also showed a dependence on the chamber aspect ratio. The centrifugal force acting on a virtual particle in the chamber was also evaluated under various conditions.

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