Dear Paul,


 I have some questions regarding a spiral tube layout silencer system that
 you have apparently developed for rotary engines.


 I am very interested to hear more about this because I am currently
 building
 a range of rotary engines for aircraft with Paul Woelfle from Germany. He
 mentioned that you had actually made one and tested it.

 Could you offer me any advice on this.

 Look forward to hearing from you and thanks very much,

 All the best, Gilo

 http://www.youtube.com/watch?v=TMWyrzisRjY

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 We have several designs that work. Th basic principle is; don't put
 anything
 in the muffler that is not cooled. It could melt and block the exit
 causing the engine to reduce power. We have had one crash where this has
 happened.
 The rotary exhaust runs a few hundred degrees F hotter than the piston
 engine so material specs are critical. If weight is critical, and it seems
 it
 is in your application, the best choice is sheet Inconel about .035 inches
 thick.

 Ram air is fed through the center pipe to cool it. The diameter
 of the exit pipe controls the noise. The smaller the diameter the
 quieter. On a 250 HP 13B p-port engine 2 inches in dia. is very quiet.
 Square entrance and exit pipes are better than round.

 Here are a few ideas.

And why is square tubing better than round?
Vlad

Good question. I am not exactly sure. My guess is it converts
a semi spherically wave front of one frequency into a complex wave front
of many frequencies. Due to the conservation of energy principle
the total energy is constant but it is divided up into many frequencies.
This, I think, converts a pure tone into a rushing sound.

Mufflers work by converting gas velocity into heat through friction
with the walls and interior parts of the muffler. The more surface area
the better.


Paul Lamar

So square tubing is better in terms of exhaust noise reduction, wounder what
effect does it have on performance vs round?
Vlad