Joe, I'd love a copy. I've a 100mb inbox so no worries. Maybe Marv would like to put it on the web and save having to email it to several people. Whoever wants a copy can just download it..

Jarrett

 

----- Original Message -----

From: Joe Ewen <jewen@comporium.net>

Date: Wednesday, February 28, 2007 12:57 pm

Subject: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re: cowl openings for water radiators

> Thomas,
> Please confirm that you want me to send it, it is a big file -
> 68MB.  Might bog you down a bit if you do not have a broad band
> connection.Joe
>  ----- Original Message -----
>  From: Thomas y Reina Jakits
>  To: Rotary motors in aircraft
>  Sent: Wednesday, February 28, 2007 1:12 PM
>  Subject: [FlyRotary] Re: Pinched ducts was : [FlyRotary] Re:
> cowl openings for water radiators
>
>
>  Yes, please send me that one or post if anyone else is interested!
>  However the real interesting thing would be to proof Ed's system
> as an alternative for a clean K&N if space is at a premium.
>
>  For me the whole project (still in the dream fase) is more about
> the modifications, building, discussions, etc. Flying the finished
> product is 2nd to everything else.
>  I make a living (more or less) flying the most fantastic
> invention ever (helicopters) in a beautiful country, so getting in
> the air is not the prime factor for planning an Experimental
> Project...
>  Thomas
>    ----- Original Message -----
>    From: Joe Ewen
>    To: Rotary motors in aircraft
>    Sent: Wednesday, February 28, 2007 1:04 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 -----
>      From: Ed Anderson
>      To: Rotary motors in aircraft
>      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.
>
>       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 {:>). 
>
>      Ed
>        ----- Original Message -----
>        From: Thomas y Reina Jakits
>        To: Rotary motors in aircraft
>        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 -----
>          From: Ed Anderson
>          To: Rotary motors in aircraft
>          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). 
>
>           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.
>
>           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? 
>
>          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 -----
>            From: John Downing
>            To: Rotary motors in aircraft
>            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 -----
>              From: Ed Anderson
>              To: Rotary motors in aircraft
>              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 -----
>                From: John Downing
>                To: Rotary motors in aircraft
>                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.
>
>
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>
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