Looks like there will be some experimenting in my future.

Ed,

Do you have any more info on the exponential horn?  I would need coordinates, formulas, drawing, or something, then I could make a trial run of all three and see which is most efficient.

Chris
----- Original Message ----- From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, March 13, 2006 8:11 PM
Subject: [FlyRotary] Re: finding a radiator

I could never find any information on the efficiency of the Wedge diffuser at subsonic speeds.  However, you are correct about the streamline duct. Measure from the core forward then truncate where you have to.  Here is the way it appears to me,  approx 1/2 of the streamline ducts pressure recover is due to the length of the duct walls the other 1/2 is due to the trumpet style flair near the core.  So say you completely eliminated the duct and just had the flair then you would get approx 42% pressure recovery (not terrible good).  So if you could incorporate 1/2 of the duct length then you would be closer to a 62% pressure recovery (getting better).   These are just rough estimates, but I have been please with the truncated streamline duct.

There is another similar duct coordinate system call the exponential horn that is easier to scale for shorter duct lengths.  It appears to be based on the same concept of the streamline of keeping the air velocity rather high until the a last minute flair of the duct to get pressure recovery. It would appear that it's efficiency would be close to the streamline and its ease of calculation might make it worth the effort alone.  But, again I have not been able to find any actually data on pressure recovery.

If I do another cooling duct experiment, it will be using the exponential horn duct just to see how it works.  But, not today {:>)

Ed

Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
----- Original Message ----- From: "rijakits" <rijakits@cwpanama.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, March 13, 2006 8:43 PM
Subject: [FlyRotary] Re: finding a radiator

If I got the idea right, to use the Streamline you would want to sketch the
"perfect" streamline for your radiator and then measure FROM the radiator
towards the intake - whatever length you can do, and cut it there.
That will be your intake area.....

Wedge should be simple: Whatever your opening is - constant cross-area to
the radiator - as big a radius at the bottom near end as you can justify -
same point top surface, start a tapper to the end of the radiator to end
about 1/2" above the far end and radius it down.

Which one is better? No idea!
Generally I would guess streamline, but in your case it will not be perfect,
so you might want to do some mockup from plywood/cardboard/etc. and try some
watermanometer tests/kitchenscale on the rooftop on top of your car -
tests.....

Thomas J.

PS: PL over at the "other" site was lofting both systems together, looks
good but results are anyones guess....

----- Original Message ----- From: "the mallorys" <candtmallory@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Monday, March 13, 2006 10:25 AM
Subject: [FlyRotary] Re: finding a radiator

Dennis,

You seem to be at the same point in installation as I.  I'm putting the
Renesis in an RV-8 using the James cowl.  I'm trying to fit the radiator
verticaly under the engine mount.  That gives me space of about 8 1/2 by

19

1/2.  Make the radiator 3.75 to 4 inches thick, and I should have enough
cooling.  Since I don't have about 50 inches in front of the radiator for
the perfect streamlined diffuser, the question for me is which will be

less

drag, a shorter (about 20 inches) streamline, or tipping the radiator at

an

angle and using a wedge shape diffuser?  In any case, I plan on having an
exit duct also with a controllable exit.

Does anyone know the answer?

Chris
----- Original Message ----- From: "Ernest Christley" <echristley@nc.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, March 12, 2006 10:37 PM
Subject: [FlyRotary] Re: finding a radiator


> Dennis Haverlah wrote:
>
>> My question is - will the air make the 75 degree turn and flow >> through
>> the fins?  If not - would turning vanes below the radiator make this
>> configuration possible?
>
> Dennis, a section in K&W book discusses this very issue.  The short

answer

> is "Yes".  The long answer is that you have to be very careful how > you
> design the duct face in front of the radiator.  If you have their > book,
> it's figure 12-12 on page 277.
>
> -- > This is by far the hardest lesson about freedom. It goes against
> instinct, and morality, to just sit back and watch people make
> mistakes. We want to help them, which means control them and their
> decisions, but in doing so we actually hurt them (and ourselves)."
>
>
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net/lists/flyrotary/


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