NNR IN RAPIDLY ROTATED METALS By - Nottingham eTheses ...

4.5 OTHER TURBINE SYSTEMS
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4.5.1 THE AXLE SUPPORTED ROTOR
This rotor system has been used by a number of workers
(34,39,44)
The hollow cylindrical rotor with a snap-on lid is supported about
its axis by a fine phosphor-bronze wire and propelled by a single
gas jet impinging against a ring of flutes about the rotor circum-
ference. Using compressed helium rotation rates of 8 kHz have
been reached. However these rotors are apparently only capable
of stable operation when the diameter/length ratio is greater than
one, which limits the volume of the sample chamber. Unfortunately
the filling factor of the rf coil is relatively poor in this system.
4.5.2 THE PRAGUE ROTOR SYSTEM
A rotor of a more conventional design has been used for the
measurement of proton magnetic resonance
(50,65)
.
The rotor
suspended in two externally pressurized conical gas bearings and
driven by two pairs of jets placed against flutes on the main
body, as shown in Figure 4.9. Using rotors machined from poly-
mers rotation speeds of 10 kHz have been achieved but, for samples
placed in hollow glass or sapphire rotors of internal diameter
3.5 mm the speeds were limited to 5 kHz. These spinning frequencies
were reportedly dependent on machining tolerances of less than
0.003 mm.
An investigation has been carried out on a similar system
directly copied from this design. When propelled by compressed
air at a pressure of 100 psi a solid nylon rotor reached a spinning
is
.