80K Turbo Compressor System Without LN2 Cooling for High Reliable and Efficient Helium Refrigerator

Abstract

In Japan’s national project ‘Super-GM,’ we developed a complete oil-free 80K turbo compressor system for the helium refrigerator which brought a remarkable reliability. This compressor has a good efficiency; nevertheless, the refrigeration system efficiency is almost same as that of a conventional refrigerator because of LN2 cooling. Then we are now developing a new conceptional cold compressor without LN2 cooling. The new compressor is driven by a coaxial expansion turbine instead of an electric motor, and the intercooling between compression stages is acted by cold helium gas which is produced by the expansion of a driving turbine. In order to make matching between compressor input and turbine output, an electric generator is provided coaxially. The efficiency of system with the new compressor is expected to improve very well. The study of system arrangement and the design of the cold compressor are reported in this paper.