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Superconducting Meissner Effect Bearings for Cryogenic Turbomachines. Phase 2

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Final rept. 1 Nov 1989-28 Feb 1994

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This is the final report of a Phase II SBIR project to develop - Meissner effect bearings for miniature cryogenic turbomachines. The bearing system was designed for use in miniature cryogenic turboexpanders in reverse- Brayton-cycle cryocoolers. These cryocoolers are designed to cool sensors on satellites. Existing gas bearings for this application must run relatively warm, so the heat leak from the bearings down the overhung shaft and into the cold process gas imposes a penalty on the cycle efficiency. By using cold Meissner effect bearings, this heat leak could be minimized and the input power per unit of cooling for these cryocoolers could be reduced. Two bearings concepts were explored in this project. The first used an all-magnetic passive radial suspension to position the shaft over a range of temperatures from room temperature to 77 K. This bearing concept was proven feasible, but impractical for the miniature high-speed turbine application since it lacked the required shaft positioning accuracy. A second bearing concept was then developed, in which the Meissner effect bearings are combined with self-acting gas bearings. The Meissner effect bearing provides the additional stiffness and damping required to stabilize the shaft at low temperature, while the gas bearing provides the necessary accuracy to allow very small turbine tip clearances 5mm and high speeds 500,000 rDm.

Subject Categories:

  • Machinery and Tools
  • Electricity and Magnetism
  • Thermodynamics
  • Unmanned Spacecraft

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