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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