X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao101.cox.net ([68.230.241.45] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTP id 2181233 for flyrotary@lancaironline.net; Mon, 16 Jul 2007 16:47:51 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.45; envelope-from=alventures@cox.net Received: from fed1rmimpo01.cox.net ([70.169.32.71]) by fed1rmmtao101.cox.net (InterMail vM.7.08.02.01 201-2186-121-102-20070209) with ESMTP id <20070716204713.JRPY1349.fed1rmmtao101.cox.net@fed1rmimpo01.cox.net> for ; Mon, 16 Jul 2007 16:47:13 -0400 Received: from BigAl ([72.192.132.90]) by fed1rmimpo01.cox.net with bizsmtp id QLnC1X00P1xAn3c0000000; Mon, 16 Jul 2007 16:47:12 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: FW: Oil cooler air flow Date: Mon, 16 Jul 2007 13:48:43 -0800 Message-ID: <000001c7c7f3$14233320$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C7C7B0.05FFF320" 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 V6.00.2900.3138 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C7C7B0.05FFF320 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable if the free air velocity (160) converts to 12"H20 and you had a = streamline duct inlet actual had that coming in then theoretically you could get = approx 12 * .84 =3D 10.8" inside the duct. Since you measured 3.25" static in = front of the core, that would indicate a significant lack of pressure recovery inside your duct (what ever the reason). There are several reasons this might be happening. I think the confusion here is whether we're talking "dynamic" pressure = or "static" pressure. Are you saying that the maximum static pressure in = the duct is 0.84 of the dynamic pressure at the entrance to the duct? If = that is true, I have been under a misconception. I measured 9.5" dynamic = pressure out in front of the scoop; and 3.25" static pressure near the face of = the core - just below the midpoint. =20 1. The air flow and velocity is considerably reduced from what you are expecting (too small opening/exit - which I don't believe to be the = case) =20 2. The boundary layer is a significant part of your duct total air = flow and as a consequence its lesser velocity has less dynamic pressure potential. =20 3. A significant part of your duct flow is chaotic with eddies which = does not provide recoverable pressure - or it is much reduced. (The boundary layer could be contributing to this) =20 4. Some combination of the above. =20 Right, now I would suspect that the boundary layer could be the culprit = in that it can contribute to 2 and 3 above. But, as you know, this is speculation on my part =20 I'm sure you're right; a combination of 2 and 3. Yesterday I measured = the static pressure near the upper surface of the duct; an inch or so in = front of the core - less than 0.25" H2O. That confirmed to me that the "flow = is chaotic with eddies", as you say. I think the addition of a vane is = worth a try. =20 Al ------=_NextPart_000_0001_01C7C7B0.05FFF320 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

if the free air velocity = (160) converts to 12"H20 and you had a streamline duct inlet actual had = that coming in then theoretically you could get approx 12 * .84 =3D = 10.8" inside the duct.  Since you measured 3.25" static in front of the = core, that would indicate a significant lack of pressure recovery inside your duct = (what ever the reason).  There are several reasons this   might be happening.

I think the confusion here is = whether we’re talking “dynamic” pressure or “static” pressure. =  Are you saying that the maximum static pressure in the duct is 0.84 of the = dynamic pressure at the entrance to the duct? If that is true, I have been under = a misconception.  I measured 9.5” dynamic pressure out in front of the scoop; and = 3.25” static pressure near the face of the core – just below the = midpoint.

 

1.  The air flow and = velocity is considerably reduced from what you are expecting (too small = opening/exit - which I don't believe to be the case)

 

2.  The boundary layer = is a significant part of your duct total  air flow  and as a = consequence its lesser velocity has less dynamic pressure = potential.

 

3.  A significant part = of your duct flow is chaotic with eddies which does not provide recoverable = pressure - or it is much reduced.  (The boundary layer could be contributing = to this)

 

4.  Some combination = of the above.

 

=

Right, now I would = suspect that the boundary layer could be the culprit in that it can contribute to 2 = and 3 above.  But, as you know, this is speculation on my = part

 

I’m sure = you’re right; a combination of 2 and 3. Yesterday I measured the static = pressure near the upper surface of the duct; an inch or so in front of the core = – less than 0.25” H2O.  That confirmed to me that the = “flow is chaotic with = eddies”, as you = say.  I think the addition of a vane is worth a try.

 

Al

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