Magnetohydrodynamic (MHD) centrifuge utilizing electric currents and magnetic fields produces a magnetic force which develops supersonic rotational velocities in gas mixtures. Device is superior to ordinary centrifuges because rotation of gas mixture is produced by MHD force rather than mechanical means

Love, W. L.

Park, C.

English

NASA Technical Reports Server

1972	 B72-10270 
NASA TECH BRIEF 
Ames Research Center 
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Separation of Gas Mixtures by Centrifugation 
Two gases differing in molecular weight can be 
separated by centrifugation, but it is necessary to 
achieve circumferential speeds significantly larger 
than the speed of sound in the gas mixture, i.e., the 
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velocity of the rotating mixture must be supersonic. 
When the gas mixture consists of very light compo-
nents (such as hydrogen and deuterium) or heavy 
components at high temperature, the speed of sound 
in the gas mixture is so large that mechanical rotation 
becomes impractical; the required rotational velocity 
is so large that centrifugal forces exceed the structural 
limits of the mechanism used to rotate the mixture. 
High rotational velocities in gas mixtures can be 
obtained in a device which may be described as a 
magnetohydrodynamic (MilD) centrifuge; it utilizes 
electric currents and magnetic fields to produce a 
magnetohydrodynamic force which develops super-
sonic rotational velocities in gas mixtures. The geom-
etry of the magnetic and electrical fields, as shown in 
the diagram, is such that the greatest force acting on 
the gas mixture occurs near the wall of the cylindrical 
chamber containing the mixture. 
The magnetohydrodynamic device is potentially 
superior to ordinary centrifuges because the rotation 
of gas mixtures is produced by an MHD force rather 
than by mechanical means; thus, the limitation in
velocity imposed by stress levels in rotating parts 
does not exist. In particular, the performance of the 
MHD centrifuge is superior to any mechanical gas 
centrifuge in instances where the component gases in 
the mixture are of small molecular weights or when 
the mixture is hot, because the required speed of ro-
tation is prohibitively large for the mechanical centri-
fuge (over 1 km/sec). 
Experiments with an MHD centrifuge have indi-
cated that with a mixture of 1.3 parts of xenon and 1 
part of helium, a 3 to 1 concentration ratio of xenon 
to helium can be obtained at the chamber walls. 
Typically, the experimental device uses 16 electrodes 
and consumes about 134 kW of power; it operates 
at pressures below 26.66 MN/M 2 (200 torr), and 
with voltage gradients of the order of 800 V/rn. The 
two magnet coils are axial and opposed in polarity; 
the radial magnetic field strength at the electrodes is 
about 0.2 tesla. 
Reference: 
Love, W. L., and Park, C.: An Experiment on the 
MHD-Driven Rotating Flow for Gas Core Nuclear 
Rocket. AIAA Journal, vol. 8, no. 8, page 1377, 1970. 
Notes: 
1. Several devices that have been reported previ-
ously incorporate MHD forces to produce a 
rotational flow in a gas; however, none have in-
corporated the particular geometry and features 
described above to provide separation of gas 
mixtures. 
2. No additional documentation is available. Speci-
fic questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: 72-10270
(continued overleaf) 
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Patent status: 
No patent action is contemplated by NASA. 
Source: Chul Park and
Wendell L. Love
Ames Research Center 
(ARC-10449) 
RE 1313 
K3C HQZ, 
-I-
B72-10270	 Category 03


Separation of gas mixtures by centrifugation

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