Steve,
A system to redirect exhaust pulses without restricting the exhaust gases is
definitely the answer and is easily achievable. I have also incorporated an
internal cooling tube and external cooling outer case, with a duel
augmentation. The trick here is to calculate that the cooling air doesn't
restrict the exhaust outlet. So I have cooling air tube augmentation (which
cools and helps extract the exhaust gases) and the exhaust gases sucking in
outside cool air (further cooling the exhaust gases).

The theory of this muffler is -as the exhaust pulse scrubs against the
mufflers inner surface the pulse noise will turn into heat. Then you need to
remove the heat. The outside case serves as a heat barrier as well.
I think I have all the bases covered - what do you think Steve. Do you and
Lynn want a drawing. Remember it will be a bit heavy and cost $200 for
parts - if you buy off the shelf. Mine is still at the welders so it is
untested as yet. I did include a reflector plate on the opposite side of the
exhaust header tube outlet and wondering now if I should have !?
George (down under)

George--yes, any configuration drawing or photos you have would be
appreciated.
Regarding introduction of additional external cooling air for mufflers, it
was avoided.
Thermodynamics aside, it adds to the overall cooling drag that is produced
by introducing air to cool heat exchangers, blast air to cool electrics, or
other .  It all adds up and the total of all  internal/cooling drag sources,
reduces efficiency and slows you down.

And if packing if used instead between the inner and outer shells for either
noise attenuation and/or damping, we could never keep material from being
pounded to dust.
This included some fairly intricate ceramic blanketmaterials.

We did fabricate a .016 stainless shell around the exhaust tubes out of the
exhaust ports.  This served two purposes.  This stainless shell was to keep
from heating air contacting exhaust tubes at the hottest section out of
ports...before it passed through the water heat exchanger(s) located behind
the engine.   Shell sections were secured by nutplates installed on 90
degree stainless sections held by the flange nuts securing the four stud
exhaust flange.

The other purpose of this shell was to hopefully provide a small safety
margin to buy some time in the event of a failure at the flange and exhaust
tubes coming out of the ports and turning the corner.

Paul or one of the our other certified smart folks who knows thermodynamics
is better qualified to opine regarding the efficacy of direcing cooling
around around the muffler.  As a general rule we tried whenever possible to
accelerate, rather than decelerate any gases from the cowling to provide
maximum velocity in relation to free stream flow.  For maximum performance
we used smallest possible diameter exhaust tubing to provide maximum
velocity and no muffler.  But for regular work, that combination is far too
obnoxious for civilians on the ground and the driver and hard on the
airframe too.
The success of the rotary engine in aircraft will be partially determined by
development of a safe, effective, lightweight, low back pressure muffer.

And regarding your cost of $200..if you are using 600 series and 321
stainless and labor for your welder, thats a hellava bargain.

Would like to see what you've done George.

Steve Beckham

OK Steve a couple of questions if you would respond. I can't quite get my
head around what you said about the exhaust manifold. I know someone used 4
studs instead of the two standard studs, but the material in that area seems
a bit on the light side. I thought perhaps a standard flange with  4
threaded holes or studs to accept a 4 hole header flange might be a better
option. This would be a flange on a flange - again more weight.

On the attached drawings [Solid-Works???]which are a collaboration between myself and Bill
Jepson, I have tried to show the cool air flow.

I take on board your comments on drag, but safety are a greater concern for
my application and cooling the exhaust will extend the life of the
 muffler - also this could be consider a mixer and a lighter muffler used
down stream and again the cooling air would make this feasible IMHO. This
would then be a very quiet set-up.

The most important part of this design is the deflectors, which was Bill's
idea. To deflect the sonic waves, which scrub around the inner can turning
into the sound into heat. The part of the design which was mine was how to
hold them in position, so I came up with the cool tube - which served two
purposes.

The rest of the design revolved around what off the shelf cones I could get
hold of. I think it came together nicely - now only if it will work, I'm
pretty sure it will.

321 would be nice, but Inconel is too expensive for this poor man's exhaust,
so I used 1.6 mm- 316SS which is an industry standard in a lot of cones
available. I'm now glad I did use the 1.6mm material.

I'm pretty sure you could get the cost of material down if you have the
contacts but that's the best I could do at that point in time.

I had a contact in the Aviation exhaust manufacture and the manufacture
everything from 321 SS plate but I was looking at $1,000 min. Not an option
for my application. I know it's cheap for the racing guys but I don't have
sponsors.

George ( down under)


Hey almost nobody has Solid Works let alone me. Send rendered jpgs only.
-- 
Paul Lamar ...No rotor no motor.

Paul,
Try these they are a screen dump of a DXF format.
George ( down under)


I don't know what you are talking about George. Windows XP cannot open
them. A screen dump would be a .png file. A DXF file is Ascii text.
Why would you want to do a screen capture of a DXF file?