In message <6F46CEA598DA4929B592072E76CCC514@LENOVOBC3751E0>, Roger L
rogerlov@ix.netcom.com> writes
>
>
>I didn't know that about the street car motors. Thanks for the info.
>For fun, simply dropping a close fitting magnet into an open vertical length
>of copper tubing is instructive....takes it a while for the magnet to travel
>down and then out the bottom. Guaranteed to amaze the kids.
>
>Now why in the world would anyone let water flow through a magnetic
>gap? Is it a case of one hand not knowing what the other is doing? A lager
>in one hand and an ale in the other?
>Air flow is bad enough. I have seen several applications where immersed
>magnetic flow measuring equipment was used to measure contaminated
>fluid flow. That kind of mismatch in goals requires constant attention and
>cleaning.
> enjoy! Roger L.
Water flow in the narrow annulus between the inner circumference of the
stator and the outer of the rotor assemblies should not be too much of
an issue (at least in fresh water). The rotor and stator poles would be
skinned in a glass-epoxy lamination or similar, so corrosion isn't an
issue. There would be frictional losses due to the shearing of the thin
water layer by the moving rotor surface against the stator surface, and
if the two were not perfectly concentric there would be some pumping
losses as the distance between the two changed slightly as the rotor
turned, but I doubt if these losses would be very high. (Provided that
ferrous silt didn't build up in the gap of course).
In sea water it would be a different matter. There would be a flow of
conductive salt water, orthogonal to the strong magnetic field in the
annular gap. Faraday's law shows that a voltage would be generated in
the sea water, and electrical currents would flow. Plenty of scope for
electrolytic corrosion in any nearby exposed metal!
BTW, submarine 'stealth' propulsion has been tried using a deliberate dc
current flowing from side to side of a pipe, having an intense magnetic
field at provided at 90 degrees to the current flow. By good old
Faraday's laws again, the water mass in the conduit will move in one
direction along the pipe, giving a certain amount of thrust as it exits.
No idea how well it worked, it's all still classified I think.
--
Chris Morriss
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