Axial and Radial Force Control for a CO2 Scroll Expander

In this study, the scroll profile of the scroll expander was designed for CO2 refrigerant in order to make use of overexpansion and to control the axial force on the thrust bearing. This approach realized that the orbiting scroll never separated from the stationary scroll even when the operating condition changed dramatically. From the analysis on the oil-film pressure forces of the main and eccentric bearings, the radial force between the scroll wraps could be controlled, which in turn contributed to a decrease in the leakage loss in the expansion process. Test results for a prototype of the scroll expander with high-pressure shell design demonstrated the volumetric efficiency as high as 96%.