X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from access.aic-fl.com ([204.49.76.2] verified) by logan.com (CommuniGate Pro SMTP 4.3.4) with ESMTP id 1005858 for flyrotary@lancaironline.net; Fri, 17 Jun 2005 23:34:45 -0400 Received-SPF: none receiver=logan.com; client-ip=204.49.76.2; envelope-from=unicorn@gdsys.net Received: from b9k4u9 (unverified [204.49.76.27]) by access.aic-fl.com (Rockliffe SMTPRA 4.5.6) with SMTP id for ; Fri, 17 Jun 2005 22:33:21 -0500 Message-ID: <001d01c573c7$c5db7ff0$1b4c31cc@b9k4u9> From: "Richard Sohn" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: small muffler suggestions for single rotor? Date: Fri, 17 Jun 2005 22:36:25 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001A_01C5738C.FEE51990" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_001A_01C5738C.FEE51990 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message ----- Original Message -----=20 From: Russell Duffy=20 To: Rotary motors in aircraft=20 Sent: Friday, June 17, 2005 7:38 PM Subject: [FlyRotary] Re: small muffler suggestions for single rotor? I have a muffler running on my test stand for several hours. It is a = tangential expansion type with nothing inside so nothing will come out. = I can stand next to the engine running witout the need of ear plugs.=20 The only critical issue is dimensions, which sometimes go against = intuision.=20 Feel free to copy it. =20 It would have to be a bit different from yours to fit the Kolb. I = suppose it could run left to right in front of the engine, rather than = under it. In order to copy the non intuitive critical dimensions, it = would help to know what they are :-) =20 Thanks, Rusty (I still owe you a visit) I never did any analytical work on this muffler design, however, I = followed the physics principals. The first muffler of this design, I = built for my SOOB in the AVID which is still flying very quietly. =20 Considering exhaust noise to be the only issue, you follow the = principle of adiabatic cooling of the exhaust gases as much as you can = afford in the available space.=20 This means trying to keep the gases as long as possible in the muffler = container, which also will add radiation and convection losses as a = benefit.=20 If you consider a container of 6" dia and 24" long physically = acceptable, the muffler is built around it. Next, in the single rotor is = only one pipe input, this input pipe enters the container tangential on = one end. The exit pipe is located on the other end of the container = rectanular to the container C/L. The exit pipe must be smaller then the = inlet pipe since the gases have less volume because of the energy loss = in the container. This is very important for keeping the expansion noise = inside the container. Keep in mind when Bubba wants to give his truck a = bigger sound he puts in a bigger tail pipe. The output pipe is between 50 and 75% of the input pipe cross section. = This will keep the back pressure in in a range where it has no = significant impact on engine power. Using this design principle on a 13B you only have to be aware of the = fact that only one input pipe counts for dimensioning the output pipe = because only one pipe is flowing exhaust gases into the muffler at any = time.=20 BTW, the muffler size in the picture was driven by the material I had, = but it works anyway. Richard Sohn N-2071U -------------------------------------------------------------------------= ----- >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_001A_01C5738C.FEE51990 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
 
----- Original Message -----
From:=20 Russell=20 Duffy
Sent: Friday, June 17, 2005 = 7:38 PM
Subject: [FlyRotary] Re: small = muffler=20 suggestions for single rotor?

I have a = muffler running=20 on my test stand for several hours. It is a tangential expansion type = with=20 nothing inside so nothing will come out. I can stand next to the = engine=20 running witout the need of ear plugs.
 
The = only critical=20 issue is dimensions, which sometimes go against intuision.=20
Feel free to copy=20 it.  
 
It would have to = be a bit=20 different from yours to fit the Kolb.   I suppose = it could=20 run left to right in front of the engine, rather than under it. =20  In order to copy the non intuitive = critical=20 dimensions, it would help to know what they are :-) =20
 
Thanks,
Rusty (I still owe = you a=20 visit)

I never did any analytical work on this = muffler=20 design, however, I followed the physics principals. The first muffler = of this=20 design, I built for my SOOB in the AVID which is still flying very=20 quietly. 

Considering exhaust noise to be the = only issue, you=20 follow the principle of adiabatic cooling of the exhaust gases as much = as you=20 can afford in the available space.

This means trying to keep the gases as = long as=20 possible in the muffler container, which also will add radiation and=20 convection losses as a benefit.

 If you consider a container of 6" = dia and 24"=20 long physically acceptable, the muffler is built around it. Next, in = the=20 single rotor is only one pipe input, this input pipe enters the = container=20 tangential on one end. The exit pipe is located on the other end of = the=20 container rectanular to the container C/L. The exit pipe must be = smaller then=20 the inlet pipe since the gases have less volume because of the energy = loss in=20 the container. This is very important for keeping the expansion noise = inside=20 the container. Keep in mind when Bubba wants to give his truck a = bigger sound=20 he puts in a bigger tail pipe.

The output pipe is between 50 and 75% = of the input=20 pipe cross section. This will keep the back pressure in in a range = where it=20 has no significant impact on engine power.

Using this design principle on a 13B = you only have=20 to be aware of the fact that only one input pipe counts for = dimensioning the=20 output pipe because only one pipe is flowing exhaust gases into the = muffler at=20 any time.

BTW, the muffler size in the picture = was driven by=20 the material I had, but it works anyway.

Richard Sohn
N-2071U

 

 

 

>>  Homepage: =20 http://www.flyrotary.com/
>>  Archive:  =20 = http://lancaironline.net/lists/flyrotary/List.html
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