Spacing between the hot rotor case and the adjacent rotor
pack is not critical for efficient engine operation. A clearance of
approximately 0.125 inch is about right -- just make sure your shaft assembly
has little or no end-play or else the disk pack will contact the housing!
Figure
C shows the outer case ring and nozzle installed. The clearance between the
outer periphery of the disks and the case ring should be about 0.125 inch.
The nozzle is simply a square or round channel welded to
the case ring and positioned tangentially to the outer edge of the disk pack.
Depending on the gas/fluid used, nozzle inserts of various diameters are secured
inside the channel to obtain the highest fluid velocity. Efficiency increases as
the square of the fluid velocity, so the faster you move the fluid, the more
efficient the engine.
Generally speaking, a convergent-divergent nozzle insert
will yield the highest fluid velocities. Also, an important design tip to keep
in mind: the width of the nozzle should never be wider than the disk pack --
this will ensure that gases will not escape past the end disks.
Figure
D shows the end plate bolted to the hot rotor case assembly. Again, the
clearance to the disk pack is sufficient at about 0.125 inch.
Lubrication
Since the life of the turbine is in its bearings, special
care must be taken in providing adequate lubrication for the speeds involved.
The best ways of becoming familiar with bearing lubrication methods are to
either download the information directly from NTN or Timken, etc. online, or
order their bearing manuals. NTN's excellent manual -- catalog #2200II/E --
provides all of the know-how for lubricating their bearings for long life in the
speed ranges we address.
For very short test runs you can simply fill the case to
the middle of the lower rolling elements -- using a high quality turbine/lathe
oil. Mobil provides an excellent DTE 24 series oil which will work in place of
turbine oil, and is relatively low cost -- about $10 to $12 per gallon.
For extended engine use, use a lubrication method as
described in the NTN manual -- splash, drip, circulation, spray, and jet, with
jet methods allowing up to three times the rated bearing speed.
Energetic Fluids
To power your turbine you may use a number of fluids
including compressed air, steam, hot gas, or a combination of all three. In
fact, for certain applications such as torque converters and transmissions you
can use heavier fluids such as water and oil.
The application of Tesla's turbine to any power situation
is only limited by the imagination!
Conclusion
Well, that about wraps it up for this series of articles.
As some of you get your engines built and running I'm sure you'll have minor
problems that need resolving. Drop us an email for help and we'll see what we
can do.
Coming up in future articles... feedback from a turbine
enthusiast who built his own pulse combustion Tesla engine!
Let us know how your project turns out!
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