Mailing List flyrotary@lancaironline.net Message #48597
From: Mike Wills <rv-4mike@cox.net>
Subject: Re: [FlyRotary] Re: Your muffler
Date: Fri, 9 Oct 2009 10:05:58 -0700
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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

 

Kelly

There you go matey. All off the shelf SS cones and tube.

George ( down under)

----- Original Message -----

From: Kelly Troyer

Sent: Thursday, October 08, 2009 9:32 PM

Subject: [FlyRotary] Your muffler

 

  George,

   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......

 

 

Thanks,

--
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)


--
Homepage:  http://www.flyrotary.com/
Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html
Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster