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----- Original Message ----- From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, October 19, 2005 1:20 PM
Subject: [FlyRotary] Re: NACA scoops
Hey, I'm not against NACA - if they work and you like them and they fit
you
need, then go for it.
The report did not say they would not work, just that they would not work
as
well as other types (streamline duct for instance) if you need pressure
recovery (decrease airflow velocity and increase pressure recovery from
dynamic energy).
However, I don't think using a streamline duct after a Naca duct is going
to
avoid the "bullet", the problem is any thing that causes a pressure
recovery
is going to cause "back pressure" to the air flow. From what I think I
understood the Naca duct is great where you keep the air velocity up (like
it being sucked into a jet engine) but don't have a lot of pressure
recovery. But whatever you have (radiator, streamline duct) that causes
back
pressure tends to adversely effect the performance of a Naca duct because
it
slows down the airflow. At least that is what I think I understood.
Since I have my ducts right up front and am not faced with some of the
challenges of the pusher type installation - I can say I don't have a dog
in
this fight {:>)
Ed A
That would go right in line with the Lycosaurus engines: Air-cooled there is
way less pressure buildup before the engine, the volume is higher though,
but that doesn't really matter as long as the air goes through easy and
takes the heat.
However once you use a radiator the pressure drop across it will ask for
some serious pressure recovery before the radiator...
Thomas J.
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