A magnetic bearing system for a high-speed cryogenic gas expander generator is presented in the paper. The expander represents a new class of such devices that, in contrast to the earlier technologies, makes use ofthe expanding gas energy by converting it into electrical power.
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Ninth International Symposium on Magnetic Bearings, August 3-6, Lexington, Kentucky, USA
MAGNETIC BEARING ACTUATOR DESIGN
FOR A GAS EXPANDER GENERATOR
Alexei V. Filatov, Patrick T. McMullen, Lawrence A. Hawkins, and Eric Blumber
CALNETIX, 12880 Moore Street, Cerritos, CA, 90703
A magnetic bearing system for a high-speed
cryogenic gas expander generator is presented. The
expander represents a new class of such devices that,
in contrast to the earlier technologies, makes use of
the expanding gas energy by converting it into
electrical power. The magnetic bearing and generator
constitute a functionally complete unit that can be
used in a variety of gas expanders utilizing different
expander wheels and operating at various speeds.
In order to obtain a compact design and increase
rotor first bending frequency, the axial magnetic
bearing is designed to have different pole areas on
different sides of the thrust disk. This results in
different load capacities in different directions,
matching operational conditions of
Regardless this anisotropy, the bearing features linear
force vs current dependence.
Radial and angular suspension of the rotor is
achieved using two patented homopolar PM-biased
radial bearings. The paper discusses design and
analysis of these bearings. In spite of the three-
dimensional nature of the electromagnetic problem,
combination of analytical solution and 2D FEA was
found to be an adequate tool for the bearing analysis.
performance have been found to be in a good
agreement with experimental data.
Gas expanders are used to extract pure gases
such as nitrogen, oxygen, and argon from the ambient
air utilizing difference in the gas condensation
temperatures (cryogenic distillation). During the
distillation process, pressurized gas spins an impeller
mounted on a shaft connected to some device that
produces drug torque, thus limiting the shaft speed