Thanks Mike,
For your kind comments, but I must emphasize
that this design is designed primarily for outside cowl use. I
understand that this, to some people, might give rise to concerns of extra
drag - but to my mind anything to get the heat out of the cowl.
For my own design I envisage the muffler sitting
within a half circle recess formed in the cowl, but there no reason that it
can't sit behind the cowl under the fuselage.
If your talking about the long under fuselage
design which forms part of the fuselage, I must admit I like that design as
well. The longer the better in my opinion, you could string a number of light
weight mufflers along a line, each feeing into the next with cooling air
mixing in, as well as cooling the OD. That would be super quiet. I
notice the best muffling ( to date) is done with more than one muffler i.e. a
primary and a secondary.
I'm not trying to convince anyone this is the
best design, merely putting it up for possible solution to the problem.
As you and others have said, off-the-shelf types aren't lasting
anywhere near long enough. Bill Jepson and I laboured over this design for
some time, before we came to the final design, I have been unable to finish my
single so haven't been able to test it yet - but it sure looks good.
George ( down under)
OK George, my memory is now jogged having seen
your drawing. I liked the design when I saw it the first time but discounted
it for my application because I couldnt see a good way to make any
muffler with a tangential entry fit my airframe. This is the same reason I
passed on Al's proven muffler design.
I think the use of cooling airflow introduced
into the muffler makes a lot of sense and this is something your design has in
common with the YO-3A muffler I've been talking about. I believe the YO-3A
design would prove superior by virtue of the greatly increased volume of the
muffler and the use of absorptive materials.
Of course until someone builds one and tries it
who knows if it will hold up to the abusive exhaust output of a rotary. But
the YO-3A design does have the advantage of being flight proven in a pretty
tough environment - low altitude recon in Vietnam.
Your muffler design (or Al's) is a winner if
the goal is to keep the muffler within the confines of the cowl. My cowl is
already too tight without a muffler in it.
Mike Wills
RV-4 N144MW
----- Original Message -----
Sent: Thursday, October 08, 2009 9:18
PM
Subject: [FlyRotary] Re: Your
muffler
Al,
Not tested yet, but have one almost complete
for the single.
The cones are there to stop the sound
waves having a direct line of sight out the rear end, the sound waves
will be going all over the place within the exhaust and I tried to replicate
that with the zig zaggy lines.
There is no restriction as the area around the
back to back cones, is equal to the area of the 2" exhaust
manifold area.
However I do take your point on swirl
restriction, but I don't see a problem as it will swirl out the end, whereas
sound waves travel in a straight line ( I think). Bill did have me put in a reflector plate opposite the
incoming exhaust, but I don't know if this will interrupt the swirl motion,
I suspect it might. The reflector plate is on the LHS of the parts count
- photo attached.
George ( down under)
George;
Nice
design. Has anyone run one of these yet.
My concern with
the tangential muffler is something called ‘swirl flow choking’ –
discovered in connection with a similar attempt with gas turbine exhaust.
High circumferential velocity tends to keep the flow from moving out
the end, and consequent pressure buildup. I don’t know whether it
applies to the pulsed flow, but it might, and your conical restriction
toward the outlet could make it worse.
To avoid that
possibility in my tangential muffler I added internal vanes at a 45 degree
angle opposite the ports, and extended the header pipes into muffler to a
squared end. Disrupts the circumferential flow and helps direct the
exhaust toward the exit.
Your depiction
of the idealized sounds waves going axially; ah-h, well; maybe/maybe
notJ.
Al
G
-----Original
Message-----
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of George
Lendich
Sent: Thursday,
October 08, 2009 1:14 PM
To: Rotary motors in
aircraft
Subject:
[FlyRotary] Re: Your muffler
There you go
matey. All off the shelf SS cones and tube.
----- Original
Message -----
Sent:
Thursday, October 08, 2009 9:32 PM
Subject:
[FlyRotary] Your muffler
Do you have a photo or drawing available of your muffler
design..........I seem to
remember
seeing some design info in the past but do not know where to find
it......
--
Kelly
Troyer
"Dyke Delta"_13B ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold
-------------- Original message from "George
Lendich" <lendich@aanet.com.au>: --------------
>
Ed,
> Cones are the GO.
>
> Any bare edge will
take a battering from the heat and shock waves. Cones
> formed
back to back eliminate any edges.
>
> There must be
supporting structure for the cones, I've used 1/4" solid
>
round bar welded into the exhaust skin.
> George (down under)
--
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