Osamu Kosuda

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%.

Development of High-efficient Compact Organic Rankine Cycle Power Generation Technology utilizing Waste Heat

As the effective utilization method of unused heat energy between 100 and 300 degree-C in the industrial sector, Organic Rankine Cycle (ORC) was selected from the viewpoint of high efficiency. The prototype of air-cooled compact ORC electric power generation system for 1kW class was evaluated in variation of the ambient temperature of condenser and the suction temperature of expander. In the experimental results, at the expander suction temperature of 175 °C and the ambient temperature of 20 °C for condenser, the generated power by the expander is 1,027W and the gross power generation efficiency is 10.3%. The net power generation efficiency, considering the input power of auxiliary equipment such as pumps and fans, is 9.0%. In the result of energy balance analysis, power consumptions of the pump and the fan are small and almost of the generated power is effectively available.