Development of a Highly Reliable Helium Refrigeration System - R&D of a Highly Reliable Helium Refrigeration System (Oil-free ype)-

摘要

The present paper reports the development of the highly reliable refrigeration system (3 types), which is applied for 70 MW class superconducting generators (SCG). R&D of the oil-free turbo type: In the turbo type of advanced refrigeration system, a complete oil-free 80 K cold compressor was developed. Moreover, the cold compressor driven by a coaxial turbine was developed to enhance the system efficiency and to save space. R&D of the oil-free screw type: In the oil-free screw rotors, taper rotors were planned to maintain a radial clearance between male and female rotors and the casing, to compensate their thermal deformation because of the heat of compression. Moreover, a seal technique was established that used a magnetic fluid an gas seals to prevent lubricating oil from bearings and the timing gear chamber into the rotor housing, under a higher rotational speed of 25,000 rpm.