Operational Experience with a Cryogenic Axial-Centrifugal Compressor

Abstract

The Large Hadron Collider (LHC), presently under construction at CERN, requires large refrigeration capacity at 1.8 K. Compression of gaseous helium at cryogenic temperatures is therefore inevitable. Together with subcontractors, Linde Kryotechnik has developed a prototype machine. This unit is based on a cryogenic axial-centrifugal compressor, running on ceramic ball bearings and driven by a variable-frequency electrical motor operating at ambient temperature. Integrated in a test facility for superconducting magnets, the machine has been commissioned without major problems and successfully gone through the acceptance test in autumn 1995. Subsequent steps were initiated to improve efficiency of this prototype. This paper describes operating experience gained so far and reports on measured performance prior to and after constructional modifications.

Analysis of the effect of friction of hybrid ball bearings on grease evaporation in cold compressors

“…For the production of superfluid helium, there are several solutions according to the needs of cryogenic systems. In large scale cryogenic systems, the cold compressor with a centrifugal impeller, which has been applied for many years, is the common equipment to depressurize the liquid helium tank in order to maintain the vacuum and obtain Helium II (superfluid helium) [1][2][3].…”

“…At present, the core components of the mainstream cold compressor are centrifugal impeller, highspeed motor and rotor-bearing system, and there are three types of bearings: active magnetic bearing, grease-lubricated rolling bearing and gas bearing. For the application of rolling bearing in cold compressor, relevant cases and descriptions have been recorded in the literature [3,4]. As the cold compressor runs at high speed, bearings are the main heat source in the motor cavity of the room temperature end.…”