Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2b8) with ESMTP id 321415 for flyrotary@lancaironline.net; Wed, 14 Jul 2004 14:36:22 -0400 Received-SPF: error receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from EDWARD (clt25-78-058.carolina.rr.com [24.25.78.58]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i6EIZmPg027085 for ; Wed, 14 Jul 2004 14:35:49 -0400 (EDT) Message-ID: <003001c469d1$628485b0$2402a8c0@EDWARD> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: New Scoop Date: Wed, 14 Jul 2004 14:35:49 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002D_01C469AF.DB3E6830" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1409 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_002D_01C469AF.DB3E6830 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Looks great, Al The dividers should help distribute the air flow evening across the = core thereby maximizing your cooling effectiveness. I agree with your = comments concerning what can be done to improve cooling flow and = diffusion. No place for the air to go except through your core. Ed Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Wednesday, July 14, 2004 1:57 PM Subject: [FlyRotary] Re: New Scoop Subject: [FlyRotary] New Scoop=20 Steve; There are all kinds of things one could say about trying to make the = scoop ideal, effective, low drag, etc; and then when you face the = reality of fitting to your plane, you can't do it. So it's what works = for you. I'll add a few comments for whatever it's worth. The intake area of the scoop should be fine. One would like to slow (expand) and turn the air entering the scoop in = a manner that maintains surface attachment for max pressure recovery and = minimum drag. This takes a much longer scoop throat than you have. The = air entering will trip to turbulent at the abrupt corner behind the B.L = dam. This will result in poor flow and pressure distribution, with most = of the air going toward the back of the scoop. I don't know what = happens in your installation downstream from the actual scoop, but you = might consider some internal baffles but get a more uniform distribution = if the rad is close to the scoop. The boundary layer dam that you have is high drag, and may be close = enough to the entrance lip that backup of the B.L. flow will be ingested = into the scoop - or it could result in some external diffusion (pressure = recovery) and allow the scoop to work just fine. The idea in the B.L. = "bleed" is to try to divert that flow somewhere else, generally off to = the sides. That would require a much more gradual diverter angle. I made a much more gradual bend in the wall of my scoop (pic) = attached. Still, in doing flow tests, I found flow separation and = turbulence which lead uneven flow distribution. I added to baffles in = the scoop get it fairly uniform. It could be that some of the = turbulence was a result of the test rig setup, although I thought I had = a long enough duct from the blower to straighten things out. The squared off internal corners will add frictional drag, but = probably not significant in overall picture. But, hey - try it. If it gives you the cooling you need, you've got = 90% of the battle won. If you feel you need to reduce drag, you can = consider that at your leisure.=20 Al =20 -------------------------------------------------------------------------= ----- >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_002D_01C469AF.DB3E6830 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Looks great, Al
 
    The dividers should = help=20 distribute the air flow evening across the core thereby maximizing your = cooling=20 effectiveness.  I agree with your comments concerning what can be = done to=20 improve cooling flow and diffusion.  No place for the air to go = except=20 through your core.
 
Ed
 
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Wednesday, July 14, 2004 = 1:57=20 PM
Subject: [FlyRotary] Re: New = Scoop

Subject: [FlyRotary] New Scoop =

 

Steve;

 

There are all kinds of = things=20 one could say about trying to make the scoop ideal, effective, low = drag, etc;=20 and then when you face the reality of fitting to your plane, you = can=92t do=20 it.  So it=92s what works for you.  I=92ll add a few = comments for=20 whatever it=92s worth.

 

The intake area of the = scoop=20 should be fine.

 

One would like to slow = (expand)=20 and turn the air entering the scoop in a manner that maintains surface = attachment for max pressure recovery and minimum drag.  This = takes a much=20 longer scoop throat than you have.  The air entering will trip to = turbulent at the abrupt corner behind the B.L dam.  This will = result in=20 poor flow and pressure distribution, with most of the air going toward = the=20 back of the scoop.  I don=92t know what happens in your = installation=20 downstream from the actual scoop, but you might consider some internal = baffles=20 but get a more uniform distribution if the rad is close to the=20 scoop.

 

The boundary layer dam = that you=20 have is high drag, and may be close enough to the entrance lip that = backup of=20 the B.L. flow will be ingested into the scoop =96 or it could result = in some=20 external diffusion (pressure recovery) and allow the scoop to work = just=20 fine.  The idea in the B.L. =93bleed=94 is to try to divert that = flow=20 somewhere else, generally  off to the sides.  That would = require a=20 much more gradual diverter angle.

 

I made a much more = gradual bend=20 in the wall of my scoop (pic) attached.  Still, in doing flow = tests, I=20 found flow separation and turbulence which lead uneven flow=20 distribution.  I added to baffles in the scoop get it fairly=20 uniform.  It could be that some of the turbulence was a result of = the=20 test rig setup, although I thought I had a long enough duct from the = blower to=20 straighten things out.

 

The squared off = internal corners=20 will add frictional drag, but probably not significant in overall=20 picture.

 

But, hey =96 try it. = If it gives=20 you the cooling you need, you=92ve got 90% of the battle won.  If = you feel=20 you need to reduce drag, you can consider that at your leisure.=20

 

Al

 

  =

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