That is interesting.  I have been thinking along the
  same lines
  recently.  I'm building a 14" disc prototype.  I
  guess my input would be
  to consider water injection as well.  I've seen posted
  the thought that
  spacers on the periphery don't degrade efficiency.  If
  you used wafer
  thin ferrite magnets you might be able to use the turbine
  as your
  alternator.  I'd be very interested in seeing any
  formulae you may have
  found in your research to calculate efficiencies, etc.
   Decker, Michael


  If you'r suggesting the magnets are also exposed to the exaust stream,
  it's a non starter. The magnets subjected to that high a temp. would
  surely reach the Curie pt where the magnetic properties go to zero.
  Robert



  Michael,

  I attached a file for you. Be warned. I don't think this guy has even
  built a unit yet.  There is some accurate historical data there on sizes
  verses output and some brief sentences of clarity but you have to filter
  out a lot of other BS, speculation and rants. Pretty much what you find
  when sifting through the Internet. I am still waiting from responses
  from people who have actually made a turbine to run off car exhaust
  gases.


  Do you have Tesla's patent?  You can find it on  the Tesla group's
  website in Milwaukee..

  14" is quite large to fly with and it will be heavy. More important it
  will have to kept slow, probably under 3,000 rpms as it becomes a large
  flywheel and can store a lot of inertia. The  G forces placed on the
  discs is in relationship to their mass and rpms.  Heating the alloys
  will weaken it even more.  There are other issues as listed below.

  Some challenges for using any turbine on the aircraft bound rotary are:
  Location, exhaust piping, loss of heat and energy in the piping and
  turbine housing, means of bypassing the turbine,  vibration isolation,
  isolating the hot components from other engine components while safely
  exhausting the heat from the cowl.  Obviously you don't want hot things
  near the water hoses, electrical wires, fuel line nor near any
  alternator or magnets.  Electrical efficiency goes down as the heat goes
  up.

  With these points  in mind it is no wonder that turbine installations
  tend to be on short well designed manifolds with little gas flow
  resistance. The heat signature is keep small and it is relatively easy
  to shield and exhaust.

  With a Tesla turbine, nozzle design is important.  I'm still clueless as
  to why though.  We do have an exhaust port that is about 2"  in
  diameter.  Do we cone it down to inch, fan it out and wrap it around.
  Coning it down will increase back pressure and concentrate the flow on
  lets say ten plates.  Leaving it wide will let it hit twenty plate.
  Narrow is good and lighter and allows flow to all come out of one side
  only.We don't know if the resulting back pressure will harm the
  engine performance.  So I have to  measure the necked down nozzle within
  the Mazda turbocharger to get an idea of what it can handle. A boosted
  p-port will be more robust no doubt.

  Placement: If the unit is on the hot side of the engine and is to spin
  the same way as the engine is rotating, the bottom of the Tesla turbines
    will have to be near or slightly above the exhaust ports. Clearing the
  intake pipe become a limiting factor in diameter size. Farther from the
  engine increases allowable diameter but also increases cowl size and
  flat plate drag as well as increasing thermal losses, in the piping,
  increases pulley mounting flange weight and increases bending moment on
  the exhaust manifold.

  Output: The shortest shaft length will be in direction of the PSRU but
  this demands the redesign of the PSRU sun shaft and torque absorber.
  Ditto pulley mount designs.  Add to this is the fact that the turbine
  position will change a little when the exhaust manifold becomes hot.
  The design has to allow for this movement or something is going to
  crack. There are unused bolts on the side housing that can be used to
  mount a angled plate with a bearing or two to handle the side force
  exerted by the multi-v belt.  I chose the PSRU side because the  sun
  shaft is supported by bearings on the engine side as well as the PSRU
  side.  No overhang which would be an issue to resolve on the accessories
  end side. I am planning a large six inch or more multi V pulley on a
  keyed sun shaft that  encapsulates the torque absorber bolted to the
  counter-weight.


  Turbine challenge.  Telsa turbines work off of boundary layer adhesion
  and are similar to the adhesion between discs in automatic
  transmissions.  Instead of oil or steam this one is running on fluid
  air.  How to calculate their  maximum hp rpm? Max torque is not at zero
  rpms. like other turbines.  Minimal torque is not at maximum rpms
  either.When forced to do work some slippage must occur if it
  overworked.  This is a good thing. The unit can be closed coupled to the
  engine because of this perhaps an sprague clutch could be used in case
  it needs to be disengaged.  The  pulley ratio would be set to obtain
  maximum turbine efficiency at say 6,000 cruise rpm.

  I believe Tesla's first unit of six plates total, had an internal width
  of less than one inch.  Disc dia. was 5.75" and it made about 30HP.
  Assuming his air power source was stronger than exhaust power and we
  will use more discs  I would be happy to get 15 HPs from each unit.

  Paul what is the wasted power in kinetic energy coming out of the 13B at
  200 hp setting.  80 hp?

  I would also love to know what the gas pressure exiting the exhaust port
  on a rotary is.  Velocity is probably near the speed of sound.


  Doug in Japan

  What is that file that you attached Doug? It had no file extension to
  identify it.

  I think the kinetic energy is higher than 8O HP in a 250 HP p-port
  engine.

  The static pressure is only a few psi. What you are interested in is the
  dynamic pressure. Lets say the exhaust speed is just subsonic at 600
  MPH. Dynamic pressure would be  936 pounds per square foot or 6.5 pounds
  per square inch.
  Lets say we have ten small wings one inch square area with a lift
  coefficient of one. Lets also say these wings are on a radius of 1.5
  inches. The torque would then be 97.5 inch pounds or 8 foot pounds at
  say 50,000 RPM. Turbine HP might then be close to 77 HP. Close to your
  estimated 80 HP. Peak HP would occur around 70,000 RPM so the HP might
  be as high as 90 or 100 HP.

  Here is an update on the heat balance of the rotary engine.

  Fully 154% of output power is wasted in the exhaust. In other words
  almost 384 HP is wasted in the exhaust of a 250 HP rotary engine. If we
  can recover only 25% of that it would be 96 recovered HP. With a few
  years of development we might get up to 35% or 134 recovered HP. The
  BSFC would drop from .47 to close .3. No gasoline burning internal
  combustion engine has ever been built to reach that low of a BSFC. That
  includes the CW R3350TC and the Napier Nomad TC diesel.

  Paul Lamar


  Thanks for the added comments.  I'm building the 14" because I want to
  try one out and 14" turned out to be the best size to maximize surface
  area/$.  I've got all my parts now and I'll be putting it together
  either this week or the last week of December.  This is a test bed to
  try to ballpark the efficiency curve.  I've not had much luck finding
  equations for that so I'm pretty much designing off of fluid dynamics.
  I'll report what I find.

  Decker, Michael

  Hey guys if the Tesla turbine is 14 inches in diameter and 2 inch wide
  and 30% air it will weigh 55 pounds. Not something one would want to
  put in an airplane.

  Paul Lamar



I would for 55 HP and a 0.1 improvement in BSFC.
Fred O.

Thats is just the turbine. It doesn't include all the other stuff you need for a
turbo compound such as a gear box and compressor.

If you could do the same thing for 20 pounds which would you choose? :)
A TO4 turbo charger weighs 16 pounds with turbine and compressor.

Paul Lamar



Tesla turbines are something I have been puzzling over for some time.  I
remember a picture of a 10" dia 3 disk turbine putting out 125hp.
http://www.teslaengine.org/main.html  has a lot of info, does anyone have a
membership? (on my wishlist)  Would it be practical to mount a (about 14"dia)
turbine inline and drive the output via another planetary reduction set?
Since the pressure is low is there some material available for a gasket to use
in a SS or Inconel Wiggins joint to compensate for heat expansion? The
lightweight PSRU idea combined with mostly sheet metal construction may be an
acceptable trade off for an additional 80+? hp and corresponding reduction in BSCF.
Dan F


Dan,

I joined as a FULL member last week for $55 so I could get access to the
membership list and a few tech papers.  Tesla turbines get a lot of
flack from traditional engineers  but so does turbocompounding a rotary
engine.

Like Michael Decker I would encourage you to build a unit and test it to
understand the technology.  Any turbo-compounding system that is going
to fly in the rotary is going to have to be compact and nearby the
exhaust ports though.

After years of researching the subject I am not at all convinced a 20lb
T4 or even a 38lb T6 size radial turbine can capture 80hp out of a 13B
at cruise rpms.  The waste power is there but now in a form that is
readily available.

What has happened I noticed is a simplification of  parts and a lowering
of expectations.
If a small Tesla turbine (around six inches in diameter can be run at
peak torque or below 18,000 rpms and it outputs 4 ft/lbs of torque. Add
to this mounting structures, traction drive, belts etc.

Up to this point the only successful turbo compounding installations have
been on huge diesels, or large aircraft engines. Don't worry about
weight in the learning stages.

Perhaps for best results we should consult with each other off of this
newsletter.  Frankly I am tired of talking about
Drop me a note at fir@gol.com.