Good ideas TJ. I agree that the
upper wall shape is not good. Didn’t concern myself that much about it
originally because I had been assured that the negative pressure at the exit above
the wing would take care of things. NOT!!!
I think I would shape it such that
there was no contraction of the area, because; based on past experience with
scoops, where you do not have external diffusion to help you out, any
contraction in the duct causes back pressure and air spilling around the scoop,
especially if you are ingesting the BL. Best if you can have continued
expansion once past the entrance.
Monty; you may well be right; it may
take a combination. However, I did put VGs in front of the entrance, and it did
not make a noticeable difference. They were only about 8” forward of
the entrance because of the gear well that is there. I think I will try again
with them further forward – on the gear door covers; and make them a bit
taller this time.
Al
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Thomas Jakits
Sent: Wednesday, July 18, 2007
4:26 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Oil
cooler inlet
please keep in mind that I am here only with theory at
this time, also I am excomunicato from PL-heaven (maybe that counts for
something?? :)).
What I gathered so far from the cooling discussions, I
would try the following in this case:
a) any of the lines I have drawn into the sketch OC
scoop-03
b) to add a little, make sure the intake lip has a
smooth lip, with the biggest possible radius on the inside
c) IF your glass finish is "absolutely
perfect" in front of the intake, I'd sand it with 400 or 360 in flow
direction: mask of the area and only sand in one direction ( I would draw the
block away from the intake...). The idea is to rough up the surface and create
miniature vortex generators
d) Try out "real" vortex generators.
However, I believe (...if your sketch
is sufficiently accurate) the most loss you see from "stall" in area
B.
The red line is rather conservative (the first one I
tried in paint :))
Bue and Magenta should get you fairly close to
streamline. Magenta pushing towards Ed's "pinched ducts" system
:)
Personally I would try some foam insert before I would
mess with turning vanes. AS your sketch looks you will not be done with a vane,
as the air still slows too much because of the excessive retreat of the the
upper duct wall....