Finn Lassen wrote:

No marked improvement on the ground (idle to 3000 RPM). Maybe a

bit

better in the cockpit

while flying. I need to run with and without several times.

Finn

Finn,

Mike Wills wrote:

  No improvement in comparison to what? Hope your not saying that

there

is

no improvement in comparison to a straight open pipe with no muffler

at

all.

Mike Wills

Jeff Spitzer wrote:

I'm really not an expert but I was afraid the pressure wave would all

come

out of the first row of holes with no particualr improvement.

Jeff Spitzer

Make them smaller and gradually larger as the wave travels down the pipe?

Paul Lamar

I really know very little about mufflers but there's two theories as far as
I know.  One is the "glasspack" approach where a perforated pipe is
surrounded by a material that converts the sound energy to friction and heat
by the motion of the packing material against itself.  The other is
generally known as a "chamber muffler" where the sound energy is used
against itself by cleverly timing the interaction of the pulses to bang into
and cancel each other.  My (unlearned) understanding was that the perforated
pipes in chamber mufflers were usually on the way out of a chamber where he
wave was allowed to burst into the chamber with full power (sudden opening)
but as the wave tries to leave it is impacted by the waves that are already
bouncing around in the chamber.  The perforated holes provide for bouncing
waves to interact with primary waves at different times thus cancelling
multiple frequencies.  I think the other goal of a chamber muffler is to
trade low frequency noise for high frequency noise which is both near or
above the upper limit of human perceptiion and less able to travel through
the atmosphere.

Jeff Spitzer

 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org