X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 50 [XX] (100%) SPAMTRICKS: long string of words Return-Path: Received: from sccrmhc11.comcast.net ([63.240.77.81] verified) by logan.com (CommuniGate Pro SMTP 5.1.7) with ESMTP id 1874891 for flyrotary@lancaironline.net; Wed, 28 Feb 2007 17:52:50 -0500 Received-SPF: none receiver=logan.com; client-ip=63.240.77.81; envelope-from=wschertz@comcast.net Received: from 7n7z201 (failure[24.7.194.231]) by comcast.net (sccrmhc11) with SMTP id <2007022822520301100kdv65e>; Wed, 28 Feb 2007 22:52:04 +0000 Message-ID: <011601c75b8b$0ff93300$e7c20718@7n7z201> From: "Bill Schertz" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: cowl openings for water radiators Date: Wed, 28 Feb 2007 16:51:52 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0111_01C75B58.BF280870" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3028 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 This is a multi-part message in MIME format. ------=_NextPart_000_0111_01C75B58.BF280870 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Joe, No problem on size, I would like a copy also. Bill Schertz KIS Cruiser # 4045 ----- Original Message -----=20 From: Joe Ewen=20 To: Rotary motors in aircraft=20 Sent: Wednesday, February 28, 2007 12:04 PM Subject: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: cowl = openings for water radiators I have a pdf of the K & W if you need it. I found the Excel sheet Ed = made reduced the K&W info into a manageable form. Joe ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Tuesday, February 27, 2007 7:46 AM Subject: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: cowl = openings for water radiators Thomas is right, Joe.=20 Lots of good stuff on cooling on Paul's site - if you want your own = copy of K&W they are long out of print. However, there was (may still = be there) a place in the Philippines that would make you a bound Xerox = copy of the book for somewhere around $30. Unless you like pouring over = a lot of math thought it makes for heavy reading {:>). =20 Ed ----- Original Message -----=20 From: Thomas y Reina Jakits=20 To: Rotary motors in aircraft=20 Sent: Monday, February 26, 2007 10:46 PM Subject: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: cowl = openings for water radiators Joe, I hate to do that, but if you need even more study stuff, go to = Paul Lamar's site and read up on the cooling chapter. He put an = impressive collection of data there and a lot of ideas - at your own = risk. There some ways that work well too (obviously, as they are = used...), but you will not find it on his site, as these ideas do not = agree with his findings. If you need something like Ed has, then you will get a lot of info = here: http://www.rotaryeng.net/cooling.html (The quoted site belongs to Paul Lamar, all info on it was = collected by him and is provid to the public by him. Where applicable = Paul Lamar holds copyrights as noted on his site...) Best Regards, Thomas Jakits, "Slim ball parasite and low life jerk" PS: Whatever one thinks about him, he does have an impressive = collection of info! ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Monday, February 26, 2007 9:38 PM Subject: [FlyRotary] Pinched ducts was : [FlyRotary] Re: cowl = openings for water radiators Actually, there is, Joe. But, you are going to be sorry you = asked {:>). I spent quite a hit of time studying a tome (Kuchuman and = Weber better know as K&W) on air cooling of liquid cooled engines = written back in the hey day of high speed mustangs lightenings, = spitfires, etc. Sort of the liquid cooling bible. Chapter 12 (the one = of most interest to us) showed a duct that reportedly had the best = pressure recovery (84% or thereabouts) around for a subsonic duct that = they had found. It was called a "StreamLine Duct" (See attached graph - = the graph a of the top graph shows the shape of the duct (or at least = 1/2 around the center line - sorry for the poor quality). =20 After quite a bit of studying and thinking about what I had = read about cooling ducts, it finally became clear to me that the perhaps = top thing that is clearly detrimental to good cooling is having flow = separation in the duct. Most of the old drawings of a cooling duct = shape followed a sinusoidal shape - rapid expansion right after the = opening. It turns out that "traditional" shape is probably one of the = worst shapes for a cooling duct (the story why is too long to get into = here). Anyhow, Flow separation leads to eddies and turbulence which = casts a "shadow" of turbulent air on the cooling core. Like a shadow, = the further away from the core the separation occurs (like near the = entrance of the duct) the larger the shadow it casts on the core area. = This "shadow" adversely interferes with the flow of air through the = core and reduces the effectiveness of the core. What causes this separation is that as pressure is recovered = by the expansion of the duct, the build up of the very pressure recover = we want - starts to hinder the boundary layer flow near the wall of the = duct. It slows it down and causes it to lose energy and attachment to = the duct wall. At a certain point the flow separates and starts to = tumble/rotate and depending where (near the duct entrance or near the = core) the flow separates, determines how much of the core area is = adversely affected. So if the boundary layer's energy level (air speed = of its molecules) is maintained at a high level separation is less = likely. So ideally, you would like to prevent any separation during = pressure recovery. The Streamline Duct is the so called "Trumpet" duct = or "Bell" duct . After the opening, there is a long section of = non-expanding duct followed by a rapid expansion into the "bell" shape = just before the core. The long non-expanding part of the duct maintains = the energy (air flow) of the boundary layer and separation does not = occur until well into the "bell" shape expansion.=20 In fact, it happens way up in the corner of the bell/core = interface and affects a very small area of the core. For full effectiveness the "Streamline duct" from K&W needs a = length of 12-17". Well, that's way more distance than I had. So I got = to thinking that if keeping the speed of the air molecules near the duct = wall helps prevent boundary layer separation and the cooling killing = eddy of turbulent air - what could I do with my short 3 - 6" (no jokes = you guys). We all know from Bernoulli that if an area is squeezed down = that the velocity of the air flow increases - right? =20 So I decided to try to maintain or increase the energy of the = air by pitching down the neck just before it goes into the bell shape = expansions in hopes that the increased energy will help the boundary = layer stay adhered to the duct wall until well into the corner of the = bell shape. So that's the story of the pinched ducts. There is no = question in my mind that this is not as effective as if I could have had = the 16" to build the duct - but, in this hobby, you work with what = you've got - right? Does it work? Who knows - but I seem to fly with less opening = area than most folks and have no cooling problems. So that's my 0.02 on = the topic - see told you, you would regret asking {:>). Ed ----- Original Message -----=20 From: John Downing=20 To: Rotary motors in aircraft=20 Sent: Monday, February 26, 2007 8:53 PM Subject: [FlyRotary] Re: cowl openings for water radiators Ed, is there some particular reason that you necked the inlet = down small, then enlarged it again. Thankyou for the pictures. JohnD ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Monday, February 26, 2007 3:39 PM Subject: [FlyRotary] Re: cowl openings for water radiators John, don't know if these photos will help. But, like you I = only have between 3 and 6" of duct distance on the radiators. You = should do Ok with 20 sq inch on each opening with a good diffuser/duct. = Attached are some photos of my current ducts. The openings are 18 sq = inches each. I have had one opening down to as little as 10 square = inches - but that was a bit marginal - so opened it back up. I have a = generous exit area for the hot air including a larger 4" x 12" bottom = opening as well as louvers on each side of the cowl. So you mileage = could vary - but Tracy has essentially the same size opening as well as = several others. Ed ----- Original Message -----=20 From: John Downing=20 To: Rotary motors in aircraft=20 Sent: Monday, February 26, 2007 12:12 PM Subject: [FlyRotary] cowl openings for water radiators What size openings do I need for the water radiators? = The Wittman Tailwind cowl I have has postal slots of 3' x 7 3/4" , which = is approx. 22 1/4 sq in. on each side. Sam James for the 160 Lycoming = is using 4 3/4' round holes which are 17.6 sq. inches on each side. My = radiators are quite close to the opening and I plan on making the = diffusers trumpet shaped, will the openings be large enough if I can = stay over 20 sq. inches on each side with a decent trumpet shape. JohnD = hushpowere II on order - hope to start in 2 weeks if weather = cooperates. ------------------------------------------------------------------ -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net/lists/flyrotary/ -------------------------------------------------------------------- -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net/lists/flyrotary/ ------------------------------------------------------------------------ -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net/lists/flyrotary/ ------=_NextPart_000_0111_01C75B58.BF280870 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Joe,
No problem on size, I would like a copy = also.
Bill Schertz
KIS Cruiser # 4045
----- Original Message -----
From:=20 Joe = Ewen=20
Sent: Wednesday, February 28, = 2007 12:04=20 PM
Subject: [FlyRotary] Re: = Pinched ducts=20 was : [FlyRotary] Re: cowl openings for water radiators

I have a pdf of the K & W if you = need=20 it.  I found the Excel sheet Ed made reduced the K&W info = into a=20 manageable form.
Joe
 
 
----- Original Message -----
From:=20 Ed Anderson
To: Rotary motors in = aircraft=20
Sent: Tuesday, February 27, = 2007 7:46=20 AM
Subject: [FlyRotary] Re: = Pinched ducts=20 was : [FlyRotary] Re: cowl openings for water radiators

Thomas is right, Joe. 
 
 Lots of good stuff on cooling on = Paul's site -=20 if you want your own copy of K&W they are long out of = print. =20 However, there was (may still be there) a place in the Philippines = that=20 would make you a bound Xerox copy of the book for somewhere around=20 $30.  Unless you like pouring over a lot of math = thought it makes=20 for heavy reading {:>). 
 
Ed
----- Original Message ----- =
From:=20 Thomas=20 y Reina Jakits
To: Rotary motors in = aircraft=20
Sent: Monday, February 26, = 2007 10:46=20 PM
Subject: [FlyRotary] Re: = Pinched=20 ducts was : [FlyRotary] Re: cowl openings for water = radiators

Joe,
 
I hate to do that, but if you = need even more=20 study stuff, go to Paul Lamar's site and read up on the cooling = chapter.=20 He put an impressive collection of data there and a lot of ideas - = at your=20 own risk. There some ways that work well too (obviously, as they = are=20 used...), but you will not find it on his site, as these ideas do = not=20 agree with his findings.
If you need something like Ed = has, then you=20 will get a lot of info here: http://www.rotaryeng.net/c= ooling.html
 
(The quoted site belongs to Paul = Lamar, all=20 info on it was collected by him and is provid to the public by = him. Where=20 applicable Paul Lamar holds copyrights as noted on his=20 site...)
 
Best Regards,
Thomas Jakits,
"Slim ball parasite and low = life=20 jerk"
 
PS: Whatever one thinks about = him, he=20 does have an impressive collection of=20 info!
 
 
----- Original Message ----- =
From:=20 Ed Anderson
To: Rotary motors in = aircraft=20
Sent: Monday, February = 26, 2007=20 9:38 PM
Subject: [FlyRotary] = Pinched ducts=20 was : [FlyRotary] Re: cowl openings for water radiators

Actually, there is, Joe.  But, you = are going=20 to be sorry you asked {:>).
 
  I spent quite a hit of time = studying a tome=20 (Kuchuman and Weber better know as K&W)  on air cooling = of=20 liquid cooled engines written back in the hey day of high speed = mustangs=20 lightenings, spitfires, etc. Sort of the liquid cooling=20 bible.   Chapter 12 (the one of most interest to us) = showed a=20 duct that reportedly had the best pressure recovery (84% or = thereabouts)=20 around for a subsonic duct that they had found.  It was = called a=20 "StreamLine Duct" (See attached graph - the graph a of the top = graph=20 shows the shape of the duct (or at least 1/2 around the center = line -=20 sorry for the poor quality).  
 
 After quite a bit of studying and = thinking=20 about what I had read about cooling ducts, it finally became = clear to me=20 that the perhaps top thing that is clearly detrimental to good = cooling=20 is having flow separation in the duct.   Most of the = old=20 drawings of a cooling duct shape followed a sinusoidal shape - = rapid=20 expansion right after the opening.  It turns out that = "traditional"=20 shape is probably one of the worst shapes for a cooling duct = (the story=20 why is too long to get into here).
 
Anyhow,  Flow separation leads to = eddies and=20 turbulence which casts a "shadow" of turbulent air on the = cooling=20 core.  Like a shadow, the further away from the core the = separation=20 occurs (like near the entrance of the duct) the larger the = shadow it=20 casts on the core area.  This "shadow"  adversely = interferes with the flow of air through the core and reduces the = effectiveness of the core.
 
  What causes this separation is = that as=20 pressure is recovered by the expansion of the duct, the build up = of the=20 very pressure recover we want -  starts to hinder the = boundary=20 layer flow near the wall of the duct.  It slows it down and = causes=20 it to lose energy and attachment to the duct wall.  At a = certain=20 point the flow separates and starts to tumble/rotate and = depending where=20 (near the duct entrance or near the core) the flow separates, = determines=20 how much of the core area is adversely affected.  So if the = boundary layer's energy level (air speed of its molecules) is = maintained=20 at a high level separation is less likely.
 
So ideally, you would like to prevent = any=20 separation during pressure recovery.  The Streamline Duct = is the so=20 called "Trumpet" duct or "Bell" duct .  After the opening, = there is=20 a long section of non-expanding duct followed by a rapid = expansion into=20 the "bell" shape just before the core.  The long = non-expanding part=20 of the duct maintains the energy (air flow) of the boundary = layer and=20 separation does not occur until well into the "bell" shape=20 expansion. 
 
 In fact, it happens way up in the = corner of=20 the bell/core interface and affects a very small area of the=20 core.
For full effectiveness the "Streamline = duct" from=20 K&W needs a length of 12-17".  Well, that's way more = distance=20 than I had.  So I got to thinking that if keeping the speed = of the=20 air molecules near the duct wall helps prevent boundary layer = separation=20 and the cooling killing eddy of turbulent air -  what could = I do=20 with my short 3 - 6" (no jokes you guys).  We all know from = Bernoulli that if an area is squeezed down that the velocity of = the air=20 flow increases - right? 
 
So I decided to try to maintain or = increase the=20 energy of the air by pitching down the neck just before it goes = into the=20 bell shape expansions in hopes that the increased energy will = help the=20 boundary layer stay adhered to the duct wall until well into the = corner=20 of the bell shape.  So that's the story of the pinched = ducts. =20 There is no question in my mind that this is not as effective as = if I=20 could have had the 16" to build the duct - but, in this hobby, = you work=20 with what you've got - right?
 
Does it work?  Who knows - but I = seem to fly=20 with less opening area than most folks and have no cooling=20 problems.  So that's my 0.02 on the topic - see told you, = you would=20 regret asking {:>).
 
Ed
 
 
----- Original Message ----- =
From:=20 John Downing =
To: Rotary motors in=20 aircraft
Sent: Monday, February = 26, 2007=20 8:53 PM
Subject: [FlyRotary] = Re: cowl=20 openings for water radiators

Ed, is there some particular = reason that=20 you necked the inlet down small, then enlarged it again.  = Thankyou for the pictures.  JohnD
----- Original Message ----- =
From:=20 Ed Anderson =
To: Rotary motors in = aircraft
Sent: Monday, = February 26, 2007=20 3:39 PM
Subject: [FlyRotary] = Re: cowl=20 openings for water radiators

John, don't know if these photos = will=20 help.  But, like you I only have between 3 and 6" of = duct=20 distance on the radiators.  You should do Ok with 20 sq = inch on=20 each opening with a good diffuser/duct.  Attached are = some=20 photos of my current ducts.  The openings are 18 sq = inches=20 each.  I have had one opening down to as little as 10 = square=20 inches - but that was a bit marginal - so opened it back = up.  I=20 have a generous exit area for the hot air including a larger = 4" x=20 12" bottom opening as well as louvers on each side of the=20 cowl.  So you mileage could vary - but Tracy has = essentially=20 the same size opening as well as several = others.
 
Ed
----- Original Message = -----
From:=20 John Downing =
To: Rotary motors = in=20 aircraft
Sent: Monday, = February 26,=20 2007 12:12 PM
Subject: = [FlyRotary] cowl=20 openings for water radiators

What size openings do I = need for the=20 water radiators?   The Wittman Tailwind cowl I = have has=20 postal slots of 3' x 7 3/4" , which is   approx. = 22 1/4=20 sq in. on each side.  Sam James for the 160 Lycoming = is using=20 4 3/4' round holes which are 17.6 sq. inches on each = side. =20 My radiators are quite close to the opening and I plan on = making=20 the diffusers trumpet shaped, will the openings be large = enough if=20 I can stay over 20 sq. inches on each side with a decent = trumpet=20 shape.  JohnD      =20 hushpowere II on order - hope to start in 2 weeks if = weather=20 cooperates.

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