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From: "rijakits" <rijakits@cwpanama.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-773629@logan.com>
Subject: Re: [FlyRotary] Re: NACA scoops
Date: Wed, 19 Oct 2005 19:45:16 -0500
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Ernest,


...... There is a subtle
> difference between "supplying air to a radiator" and "using a NACA inlet
> for pressure recovery."  The subtlety is the root of the argument.  Just
> because it isn't good a pressure recovery doesn't mean that it will make
> a bad cooling inlet.  It only means that you will have to do some
> pressure recovery in some other way, like a streamlined duct.  "We don't
> THINK it will work for radiators, because there isn't enough pressure
> recovery" IS a long way from "it can't supply air to a radiator and you
> shouldn't waste your time trying ***because the inventors said so***".
> I'm only objecting to the very last clause.  The authors might fully
> agree that a submerged inlet is a perfect compliment to a streamlined
> duct. The submerged inlet collects air in a low drag manner which it
> does well, and the streamline duct is responsible for pressure recovery
> which IT does well.  But we don't know that, 'cause they don't make any
> attempt to speak to it.  I think it would be appropriate to assert that
> the authors would agree with the statement that sticking a radiator
> against the back end of a NACA inlet is only marginally better for
> cooling than hanging it out the bottom of the fuselage.
.........

That's precisely what I want to test sometime!
Intuitively I'd rather lean towards a ram intake with a streamline diffuser,
followed by some kind of suction exit (exhaust augmenter or just
slipstream).
But it might be a 50/50 game at the end...... as you said, at the end one
has to look at the whole system not just ata single part!
I really started to get interested in all that diffuser stuff after reading
about Dave Anders RV-4 (Cafe Foundation) and Brian Schmidtbauer's Mustang II
( Kitplane Feb.2004). They also point to Hoerners books (Fluid dynamic drag)
and came up with a intake/outlet ratio of 78% - intake being bigger (comon
practise was outlet 150% of inlet...)

I still didn't find the part about the P-51 with the modified cooling-scoop,
the one more efficient, but still didn't make production...

....and all to reduce cooling drag (which is a big performance eater if not
kept at bay)


Thomas J. :)