Return-Path: Received: from fed1mtao02.cox.net ([68.6.19.243] verified) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2753220 for flyrotary@lancaironline.net; Thu, 20 Nov 2003 10:41:53 -0500 Received: from BigAl ([68.107.116.221]) by fed1mtao02.cox.net (InterMail vM.5.01.06.05 201-253-122-130-105-20030824) with ESMTP id <20031120154148.OCNV27510.fed1mtao02.cox.net@BigAl> for ; Thu, 20 Nov 2003 10:41:48 -0500 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Core vs Radistor was Re: [FlyRotary] radiator Date: Thu, 20 Nov 2003 07:41:47 -0800 Message-ID: <000001c3af7c$cefa1fd0$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C3AF39.C0D6DFD0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4024 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C3AF39.C0D6DFD0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit I was curious as to what the side 'rails' are that are located on each side of the inlet ramp to the duct. Those are boundary layer deflectors. The original NACA papers on these scoops talk about improving NACA ducts by having those deflectors. The boundary layer is the real problem with submerged inlets, especially toward the aft end of the fuselage where the boundary layer is fully developed. The boundary layer is, as you probably know, slower moving air near the surface where it has been slowed down by friction with the surface. I think one of the major problems w/ the Naca ducts used in this application is that they should still be placed in an area of high pressure. I my humble opinion, right behind the thickest part of the fuse isn't really a high pressure location. However having said that.. I'm not sure where else he could have put them unless he had wanted to do alot of ducting. I think that's why he put those little VG's where they are. It would appear that he was having problems w/ airflow velocity [boundary layer thickness] and by adding the vg's he re-energized or speed up/thinned down the boundary layer and improved the airflow into his ducts. Experiments is recent years have found that strategic placement of VGs in front of a NACA scoops make significant improvement. By setting up two vortices (spirals in the air flow) going in different directions (notice the two VGs are placed at opposite angles), you can separate the boundary layer and spiral some of the faster moving air into the duct. Placing NACA scoops toward the front of the fuselage generally pits them where the boundary layer is thinner and the pressure is higher. It depends a lot on the fuselage shape, but is generally good surface pressure recovery toward the aft end of the fuselage (or aft edge of the wing), so a NACA scoop can work reasonably well toward the back of the fuselage where the boundary layer flow will be forced into the scoop by a pressure differential between the scoop inlet and wherever the air is making its exit, and/or if you can do something about the boundary layer, like using the VGs. Of course you will never get a submerged scoop to give you the efficiency of a ram air scoop, but you might get up to about 80%. Al ------=_NextPart_000_0001_01C3AF39.C0D6DFD0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

I was curious as to what the side 'rails' are

that are located on each side of the inlet ramp to the duct. =

Those are boundary layer deflectors. The = original NACA papers on these scoops talk about improving NACA ducts by having = those deflectors. The boundary layer is the real problem with submerged = inlets, especially toward the aft end of the fuselage where the boundary layer = is fully developed. The boundary layer is, as you probably know, slower = moving air near the surface where it has been slowed down by friction with the = surface.

I think one of the major problems w/ the Naca

ducts used in this application is that they should still be placed in = an

area of high pressure. I my humble opinion, right behind the thickest = part

of the fuse isn't really a high pressure location. However having = said

that.. I'm not sure where else he could have put them unless he had = wanted

to do alot of ducting. I think that's why he put those little VG's = where

they are. It would appear that he was having problems w/ airflow = velocity

[boundary layer thickness] and by adding the vg's he re-energized or = speed

up/thinned down the boundary layer and improved the airflow into his = ducts.

Experiments is recent years have found that = strategic placement of VGs in front of a NACA scoops make significant = improvement. By setting up two vortices (spirals in the air flow) going in different directions (notice the two VGs are placed at opposite angles), you can = separate the boundary layer and spiral some of the faster moving air into the = duct.

Placing NACA scoops toward the front of the = fuselage generally pits them where the boundary layer is thinner and the pressure = is higher. It depends a lot on the fuselage shape, but is generally = good surface pressure recovery toward the aft end of the fuselage (or aft = edge of the wing), so a NACA scoop can work reasonably well toward the back of = the fuselage where the boundary layer flow will be forced into the scoop by = a pressure differential between the scoop inlet and wherever the air is = making its exit, and/or if you can do something about the boundary layer, like = using the VGs.

Of course you will never get a submerged scoop to = give you the efficiency of a ram air scoop, but you might get up to about = 80%.

Al

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