Compressor, Oil separation, Oil discharge, CO2, refrigerant, Hydro fluorocarbon, CFD
A CO2 rotary compresspr uses refrigeration oil to lubricate and cool sliding parts and to seal the cylinder. It is difficult to separate the oil inside the shell at high pressure from CO2 gas, whose difference in density from the oil is small. It remains an issue to retain high efficiency with the same shell size as a present hydro fluorocarbon (HFC) compressor. We explored an improvement in the oil separation by use of CFD analysis and identified two effective measures. One measure is to flatten a lower balance weight of the rotor to prevent the oil mist from moving up through the motor flow paths. Another measure is to set up a rotating disc over a protruding balance weight at the top of the rotor to increase the pressure in the upper space and allow the oil over the stator to return to the lower space by gravity. Experiments with an actual compressor verify that oil separation is improved to the target value.