Return-Path: Received: from [65.54.169.56] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 856559 for flyrotary@lancaironline.net; Tue, 05 Apr 2005 21:23:02 -0400 Received-SPF: pass receiver=logan.com; client-ip=65.54.169.56; envelope-from=lors01@msn.com Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Tue, 5 Apr 2005 18:22:18 -0700 Message-ID: Received: from 4.174.5.74 by BAY3-DAV26.phx.gbl with DAV; Wed, 06 Apr 2005 01:22:18 +0000 X-Originating-IP: [4.174.5.74] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: A lot to learn Date: Tue, 5 Apr 2005 21:22:13 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0048_01C53A25.89089850" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.10.0011.1703 Seal-Send-Time: Tue, 5 Apr 2005 21:22:13 -0400 X-OriginalArrivalTime: 06 Apr 2005 01:22:18.0484 (UTC) FILETIME=[12F19B40:01C53A47] This is a multi-part message in MIME format. ------=_NextPart_000_0048_01C53A25.89089850 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I'm generalizing, but in your example, the slow plane might cool OK in = cruise but overheat at its climb speed of 65-70 mph. Tracy Hi! Guys=20 I' m showing my ignorance but you all lost me in the cooling = discussion. Correct me if I'm wrong , If coolant temperature on an RV on = climb out at 100mph full throttle stay within limits wouldn't a slow = airplane with a top speed of say 125MPH be able to use the same cooling = system set up? or those the fact that an RV has less drag come into it? Georges Boucher ( notice " No fiddly things" at the bottom of = the page) -------Original Message------- From: Rotary motors in = aircraft Date: 04/05/05 07:34:41 To: Rotary motors in = aircraft Subject: [FlyRotary] Re: A lot to learn See, I told you this was the most miss-understood detail in = water cooled engines! : ) FWIW, here is my summary of the discussion so far: Ed, you are being way too modest. Yours has been the most = coherent real world analysis so far while still tying it to the = theoretical groundwork. Your brief departure into the irrelevant = molecular velocity (for this discussion), was in response to someone = else, not your fault. Jim, excellent point, we must separate the irrelevant and = 'things we can't do anything about' from the discussion about building a = actual honest to god flying machine. Doug's 'rule of thumb' post was based on real physics but left = out some factors that made it not universally applicable. What works = for an RV will not necessarily work for a Pietenpole, even if they had = the same size engine. And while the military must design for "Std air + = 40 deg F" (100 degrees), we have the advantage of not needing to design = to that standard. On those very hot days, I can accept the limitation = of using a lower power setting in climb in order to have other = advantages. I'm not scrambling to intercept MiGs at 40,000 ft. But = Doug's point of using rules of thumb (when accurate and applicable), is = very true. Very few builders have the time or inclination to fully = absorb K & W (which he has done pretty well). Tracy 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 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=20 =20 =20 No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.9.1 - Release Date: 4/1/2005 >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0048_01C53A25.89089850 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
I'm generalizing,  but in your example,  the slow plane = might=20 cool OK in cruise but overheat at its climb speed of 65-70 mph.
 
Tracy
 

Hi! Guys 
I' m showing my ignorance but you all lost me in the = cooling=20 discussion. Correct me if I'm wrong , If coolant temperature on = an RV on=20 climb out at 100mph full throttle stay within limits wouldn't a = slow=20 airplane with a top speed of say 125MPH be able to use the same = cooling=20 system set up? or those the fact that an RV has less drag come = into=20 it?
Georges Boucher ( notice " No fiddly things" at the bottom = of the=20 page)
 
-------Original=20 Message-------
 
From: Rotary motors in=20 aircraft
Date: = 04/05/05=20 07:34:41
To: Rotary motors in=20 aircraft
Subject: = [FlyRotary]=20 Re: A lot to learn
 
See, I told you this was the most miss-understood detail in = water=20 cooled engines!  : )
 
FWIW, here is my summary of the discussion so far:
 
Ed, you are being way too modest.  Yours has been the = most=20 coherent real world analysis so far while still tying it to the=20 theoretical groundwork.  Your brief departure into the = irrelevant=20 molecular velocity (for this discussion), was in = response to=20 someone else, not your fault.
 
Jim, excellent point, we must separate the irrelevant and = 'things=20 we can't do anything about' from the discussion about building a = actual=20 honest to god flying machine.
 
Doug's 'rule of thumb' post was based on real physics but = left out=20 some factors that made it not universally applicable.  What = works=20 for an RV will not necessarily work for a Pietenpole, even if = they had=20 the same size engine.  And while the military must design = for "Std=20 air + 40 deg F" (100 degrees), we have the advantage of not = needing to=20 design to that standard.  On those very hot days, I can = accept the=20 limitation of using a lower power setting in climb in order to = have=20 other advantages.  I'm not scrambling to intercept MiGs at = 40,000=20 ft.  But Doug's point of using rules of thumb (when = accurate and=20 applicable), is very true.  Very few builders have the time = or=20 inclination to fully absorb K & W (which he has done pretty=20 well).
 
Tracy
Ok, Jim
 
I agree that the theory part = gets out of=20 hand at times (my fault).  Theory only counts if it works = in=20 practice {:>).  However, I think these question = naturally arise=20 when we start talking about some of this stuff - the old "how it = do=20 that". 
 
The only part  that really = counted was=20 understanding what was necessary to keep air flow from = separating from=20 the walls in a diffuser.  If you eliminate that problem you = have=20 done probably 90% of what you can do to achieve optimum diffuser = performance (my opinion of course).  So you can have = otherwise=20 adequate core surface and volume, but if you have a poor duct = design=20 with lots of flow separation and eddies then your system may = fail to=20 adequately cool.
 
Ed A
 

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

If the = purpose of the=20 plenum is pressure recovery (converting dynamic pressure into = static=20 pressure) and it's the static pressure drop that drives the mass = of air=20 through the radiator core, why not just forget about the = molecular,=20 boundary layer and core passage size considerations for the = moment since=20 we can't quantify any of that anyway.  As Ed has stated so = many=20 times in so many ways, a good inlet/plenum design does a better = job of=20 converting dynamic pressure to static pressure than a bad one, = and he's=20 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=20 radiator and we've got the pressure drop across the core. =20 Period.  We know how close we are to Ed's plenum.  = Then adapt=20 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=20 kias drop across the radiator at cruise.  More is = better.  If=20 I don't have sufficient pressure drop across the radiator, I = probably=20 need to improve my intake and plenum to get rid of the eddies Ed = alludes=20 to.  That is what I've got the most influence over.  = If I=20 don't get enough pressure recovery, I study Ed's findings and = approach=20 implement them better. 

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

    
  

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