X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao07.cox.net ([68.230.241.32] verified) by logan.com (CommuniGate Pro SMTP 5.1c.2) with ESMTP id 1317894 for flyrotary@lancaironline.net; Thu, 27 Jul 2006 00:48:02 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.32; envelope-from=ALVentures@cox.net Received: from BigAl ([72.192.132.90]) by fed1rmmtao07.cox.net (InterMail vM.6.01.06.01 201-2131-130-101-20060113) with ESMTP id <20060727044713.XUPA11027.fed1rmmtao07.cox.net@BigAl> for ; Thu, 27 Jul 2006 00:47:13 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Exhaust pipes Date: Wed, 26 Jul 2006 21:47:20 -0700 Message-ID: <000001c6b137$bedb5280$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C6B0FD.127EC470" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C6B0FD.127EC470 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable From the pictures of his exhaust system, it appears that the pipes were supporting the muffler can. My understanding, is that the entire = exhaust will glow red, and the metal will soften (as in almost melt) at high = power settings. The melting point of inconel is over 2500F. Things will start to glow = at about 1000F if the light isn't too bright. It is still quite strong at = our exhaust temps. It is worth noting that one of the features of expanding = the gas into the large tube is that the temperature drops (Charle's Law of expanding gases); the temp of the large tube is somewhat below the temp = in the header (how much lower depends on too many factors that I don't = know) and depends on backpressure and engine rpm. =20 Al W. brings up a good point. I had been primarily considering thermal stress, but stress due to vibration from the engine (aside from exhaust pulses) could be a major factor. Some high frequency resonance with = engine vibration could do a job on the welds where joe's broke; or a resonance = with the unsupported exit pipe? =20 I guess I'll learn some more as I accumulate some hours on my plane. = Now a real challenge is coming up with some kind of damping support . . . .=20 =20 Al G. ------=_NextPart_000_0001_01C6B0FD.127EC470 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable


From the pictures of his exhaust system, it appears that the pipes were supporting the muffler can.  My understanding, is that the entire = exhaust will glow red, and the metal will soften (as in almost melt) at high = power settings.

The melting point of inconel is = over 2500F.  Things will start to glow at about 1000F if the light = isn’t too bright.  It is still quite strong at our exhaust temps.  = It is worth noting that one of the features of expanding the gas into the = large tube is that the temperature drops (Charle’s Law of expanding gases); = the temp of the large tube is somewhat below the temp in the header (how much = lower depends on too many factors that I don’t know) and depends on = backpressure and engine rpm.

 

Al W. brings up a good point. I = had been primarily considering thermal stress, but stress due to vibration from = the engine  (aside from exhaust pulses) could be a major factor.  Some = high frequency resonance with  engine vibration could do a job on the = welds where joe’s broke; or a resonance with the unsupported exit = pipe?

 

I guess I’ll learn some = more as I accumulate some hours on my plane.  Now a real challenge is coming = up with some kind of damping support . . . .

 

Al G.

------=_NextPart_000_0001_01C6B0FD.127EC470--