Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 854383 for flyrotary@lancaironline.net; Mon, 04 Apr 2005 12:59:14 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-185-127.carolina.res.rr.com [24.74.185.127]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j34GwQLw011221 for ; Mon, 4 Apr 2005 12:58:28 -0400 (EDT) Message-ID: <000601c53937$85b3ba20$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: A lot to learn Date: Mon, 4 Apr 2005 12:58:27 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0003_01C53915.FE6B2BA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0003_01C53915.FE6B2BA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ok, Jim I agree that the theory part gets out of hand at times (my fault). = Theory only counts if it works in practice {:>). However, I think these = question naturally arise when we start talking about some of this stuff = - the old "how it do that". =20 The only part that really counted was understanding what was necessary = to keep air flow from separating from the walls in a diffuser. If you = eliminate that problem you have done probably 90% of what you can do to = achieve optimum diffuser performance (my opinion of course). So you can = have otherwise adequate core surface and volume, but if you have a poor = duct design with lots of flow separation and eddies then your system may = fail to adequately cool. Ed A ----- Original Message -----=20 From: Jim Sower=20 To: Rotary motors in aircraft=20 Sent: Monday, April 04, 2005 12:29 PM Subject: [FlyRotary] Re: A lot to learn Is it possible we're dismissing some important factors getting a = little out of our depth here? Dynamic pressure in the cores and across = the cores would seem to be so highly dependent on surface friction and = core density and passage size as to be impossible to estimate, much less = quantify accurately. If the purpose of the plenum is pressure recovery (converting dynamic = pressure into static pressure) and it's the static pressure drop that = drives the mass of air through the radiator core, why not just forget = about the molecular, boundary layer and core passage size considerations = for the moment since we can't quantify any of that anyway. As Ed has = stated so many times in so many ways, a good inlet/plenum design does a = better job of converting dynamic pressure to static pressure than a bad = one, and he's found out pretty much what he has to do to make a bad one = good. =20 If we measure static pressure at the forward and aft face of the = radiator and we've got the pressure drop across the core. Period. We = know how close we are to Ed's plenum. Then adapt the stuff that Ed has = pioneered for us to make it better An Airspeed indicator I find is = handier and more accurate than a water manometer. The Pitot connection = on the upwind side and the Static connection on the downwind side should = give me upwards of 100, maybe 120 kias drop across the radiator at = cruise. More is better. If I don't have sufficient pressure drop = across the radiator, I probably need to improve my intake and plenum to = get rid of the eddies Ed alludes to. That is what I've got the most = influence over. If I don't get enough pressure recovery, I study Ed's = findings and approach implement them better. =20 I think all this molecular stuff is more appropriate to the ACRE list = where nothing ever really has to fly. This list (to me) is the guys who = actually FLY. A sound qualitative analysis of the issues involved = (which we already have) will lead me to a workable solution. That is = very nice since an acceptably accurate quantitative analysis is not = possible. To that end (to coin a phrase) I don't have to know how it = works or why it works, I only have to know what I have to do to MAKE it = work. And I have been blessed that Ed has found out most of this. Are we PVORT. again? ... Jim S. David Carter wrote: ----- Original Message -----=20 From: To: "Rotary motors in aircraft" Sent: Monday, April 04, 2005 7:07 AM Subject: [FlyRotary] Re: A lot to learn ! Re: Cooling -Learned a lot Charlie E wrote: At the risk of embarrassing myself with a display of misunderstanding the physics of it all, should your pressure sensors be measuring dynamic pressure or static? Seems like I remember Tracy's measurement pics having foam chunks over the pressure sensors to remove the dynamic component of the pressure measurement. I couldn't remember if your setup has that (& I really don't know if it should, either). Charlie --------------------------------------------- =20 >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0003_01C53915.FE6B2BA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ok, Jim
 
I agree that the theory part gets out = of hand at=20 times (my fault).  Theory only counts if it works in practice=20 {:>).  However, I think these question naturally arise when we = start=20 talking about some of this stuff - the old "how it do that".  =
 
The only part  that really counted = was=20 understanding what was necessary to keep air flow from separating from = the walls=20 in a diffuser.  If you eliminate that problem you have done = probably 90% of=20 what you can do to achieve optimum diffuser performance (my opinion of=20 course).  So you can have otherwise adequate core surface and = volume, but=20 if you have a poor duct design with lots of flow separation and eddies = then your=20 system may fail to adequately cool.
 
Ed A
 
 
 
 
----- Original Message -----
From:=20 Jim=20 Sower
Sent: Monday, April 04, 2005 = 12:29=20 PM
Subject: [FlyRotary] Re: A lot = to=20 learn

Is it possible we're dismissing some important factors = getting=20 a little out of our depth here?  Dynamic pressure in the cores = and across=20 the cores would seem to be so highly dependent on surface friction and = core=20 density and passage size as to be impossible to estimate, much less = quantify=20 accurately.

If the purpose of the plenum is pressure recovery=20 (converting dynamic pressure into static pressure) and it's the static = pressure drop that drives the mass of air through the radiator core, = why not=20 just forget about the molecular, boundary layer and core passage size=20 considerations for the moment since we can't quantify any of that=20 anyway.  As Ed has stated so many times in so many ways, a good=20 inlet/plenum design does a better job of converting dynamic pressure = to static=20 pressure than a bad one, and he's found out pretty much what he has to = do to=20 make a bad one good. 

If we measure static pressure at = the=20 forward and aft face of the radiator and we've got the pressure drop = across=20 the core.  Period.  We know how close we are to Ed's = plenum. =20 Then adapt the stuff that Ed has pioneered for us to make it = better  An=20 Airspeed indicator I find is handier and more accurate than a water=20 manometer.  The Pitot connection on the upwind side and the = Static=20 connection on the downwind side should give me upwards of 100, maybe = 120 kias=20 drop across the radiator at cruise.  More is better.  If I = don't=20 have sufficient pressure drop across the radiator, I probably need to = improve=20 my intake and plenum to get rid of the eddies Ed alludes to.  = That is=20 what I've got the most influence over.  If I don't get enough = pressure=20 recovery, I study Ed's findings and approach implement them = better. =20

I think all this molecular stuff is more appropriate to the = ACRE list=20 where nothing ever really has to fly.  This list (to me) is the = guys who=20 actually FLY.  A sound qualitative analysis of the issues = involved=20 (which we already have) will lead me to a workable solution.  = That is=20 very nice since an acceptably accurate quantitative analysis is = not=20 possible.  To that end (to coin a phrase) I don't have to know = how it=20 works or why it works, I only have to know what I have to do to MAKE = it=20 work.  And I have been blessed that Ed has found out most of=20 this.

Are we PVORT. again? ... Jim S.


David Carter=20 wrote:
----- Original Message -----=20
From: <jbker@juno.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.n=
et>
Sent: Monday, April 04, 2005 7:07 AM
Subject: [FlyRotary] Re: A lot to learn ! Re: Cooling -Learned a lot


  
Charlie E wrote:

At the risk of embarrassing myself with a display of misunderstanding
the physics of it all, should your pressure sensors be measuring dynamic
pressure or static? Seems like I remember Tracy's measurement pics
having foam chunks over the pressure sensors to remove the dynamic
component of the pressure measurement. I couldn't remember if your setup
has that (& I really don't know if it should, either).

Charlie
---------------------------------------------

    
  

>>  Homepage:  http://www.flyrotary.com/

>>  Archive:   =
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