Paul,

  Just playing around with some ideas on TC..This concept I am sending for
  critique, understanding that this was put together in just a few
  minutes...

  The Idea here is to bolt the 2 exhaust housings up close and personal,
  with some kind of adapter so they align with a sandwiched gear box that
  resides where the compressor used to be, reducing rpm to the upper
  shafts..

  One shaft translates outbound to the single compressor in a housing
  where it bumps the rpm back up to compressor speeds needed..the other
  translate in the opposite direction that reduces rpm for the compound..

  You can see built as oune complete body but don't have to tell you this
  is all very modular with gear box housing and shaft housings as
  separate..

  All gear ratios and dimensions will adjust obliviously according to
  design load and clearances..Certainly supported on the ends for rigidity
  as well...

  Jim talked about getting the turbo close to the exhaust port and also
  keeping the compound shaft in perfect alignment outboard, this may be a
  solution....


  Be nice, I am very sensitive as you know...

  jeff


  No jpeg attached??????

  jeff

  Sorry Jeff. I think you are gearing it up and not
  down.

  Paul Lamar

 Jeff, Although I haven't done the CAD work on this I did research to find
 out what type of system to use. There are manifolds allowing substitution of
 one large turbocharger on a 13B which  is thought to extract more power than
 the two stock turbines which are limited in size due to the tight spacing.

 Although you could connect two hot side turbines with an inconel coupling
 that is a really harsh environment and temperature expansion has to be
 considered.  The major problem with turbo compounding is the 12 to 1 speed
 reduction needed to connect back to the engine shaft. This is done with a
 traction drive by rotrax or more commonly with multistage spurr gears by
 procharger. To put these off the shelf items together the shaft of the
 turbo supercharger would have to be replaced with one slightly longer and
 providing a coupling for the procharger gearbox. Also  needed is a bearing
 housing fabricated to fit the compressor air horn inlet with the opposite
 end adapted to the procharger gearbox. As with your model above the engine
 drives the compressor at low speed and the exhaust  turbine drives
 everything at high speed. A waste gate is still needed in case the gearbox
 becomes disconnected from the engine shaft.

         I have seen an advertisement on the Internet for an assembled unit
 incorporating these design features as a kit for isuzu engines which is
 available only in Japan. The compounded supercharger is built by
 rotrax and manufactured  in Holland.  I couldn't get any information from
 rotrax or a price. There is apparently only one size and I don't know the
 displacement of the isuzu engine it is used on or the amount of boost.

       The shaft seems like a great excuse to use your CNC lathe. There are
 steps, precision journals, tapers, and threads. It would also seem that
 splines for a coupe ling might be necessary since it runs at 100K RPM.

      The torque of the high speed shaft should peak under 30 ft lbs at
 start up and  fall to 7 ft lbs at full speed. I like the one large
 turbocharger because it can  have a larger diameter shaft which would be
 better to adapt a coupling to.

        One question about your design above. Are you gearing down to the
 drive shaft then gearing back up to get a different speed  on the compressor
 than the exhaust turbine rather than having them run 1 to 1 ?

 george grimes

 Doug Fir has a rotrex George.

 Here is some info. I am using the same friction gear box in my design.


 Paul Lamar



Paul,

My recollection is that turbine efficiency is somewhat tied to RPM
because the speed of the gas flow must be matched to the speed of the
turbine blade..  Why not go to a larger turbine which would allow a
lower RPM for a given blade speed?  I realize a larger turbine might
be heavier overall, but if it were limited to a lower RPM, savings
might be possible.

RPM (Speed) is directly related to circumference, which has a linear
relationship to diameter..  Double the diameter of the exhaust, and
that should halve the RPM for a given blade speed.  We'd want a very
large exhaust wheel with very tight flows compared to what's probably
already on the market.

I wonder if it would be cheaper to have a custom turbine wheel made
for an existing large housing than to use a design that requires such
a large and high speed reduction ratio.  It would certainly be
simpler.

I know we have talked about a direct drive to the e-shaft system in
the past, but I think an intermediate step that only required a 3:1
reduction might be worth considering.


Regards,

Matt-

The key is blade velocity as a ratio of gas velocity out of the nozzle.
The A/R relates to the nozzle.

Torque is a maximum when the blade is stalled and zero when
blade velocity equals gas velocity.

Here is the HP out.

Paul Lamar