Clearance leakage flow and thermodynamic performance of CO₂ co-rotating scroll compressor for electric vehicle thermal management systems

The CO₂ scroll compressor inevitably occurs clearance leakage, resulting in a reduction in thermodynamics performance. This study establishes unsteady throughflow model of CO₂ co-rotating scroll compressor considering axial and radial clearances to investigate the clearance leakage flow characteristics and thermodynamic performance of CO₂ compressor. Then the relationship between axial clearance leakage and pressure variation is revealed in the suction, compression and discharge process. Finally, effect of rotational speed on the performance of CO₂ compressor is investigated with different leakage clearances. The results demonstrate effect of axial clearance leakage on the volumetric and isentropic efficiency of compressor is more significant than radial clearance leakage. An increase of axial clearance leakage flow increases pre-compression in the suction process, reduces over-compression with 0 μm to 26 μm axial clearance and causes under-compression with 28 μm to 30 μm axial clearance in the compression, and alleviates the asymmetric pressure distribution in the discharge process. As the crank angle from 180 deg to 360 deg in suction process, the pressure difference between adjacent chamber mainly determines the radial leakage with 0 μm to 24 μm axial clearance, while the leakage line length mainly determines the radial leakage with 26 μm to 30 μm axial clearance. An increase in rotational speed can lead to a more significant improvement in volumetric efficiency and critical failure axial clearance through delaying the suction backflow moment and reducing axial clearance leakage flow. The research results provide a theoretical guidance for the leakage clearance size control and performance improvement of CO₂ co-rotating scroll compressor.