|
|
Al,
Do you
have any photos of your oil cooler install showing the airflow
path?
Joe Berki
Limo EZ
At 10:57 AM 7/14/2004 -0700, Al Gietzen wrote:
Subject: [FlyRotary]
New Scoop
Steve;
There are all kinds of things one could say
about trying to make the scoop ideal, effective, low drag, etc; and then
when you face the reality of fitting to your plane, you can t do
it. So it s what works for you. I ll add a few comments for
whatever it s worth.
The intake area of the scoop should be
fine.
One would like to slow (expand) and turn the
air entering the scoop in a manner that maintains surface attachment for
max pressure recovery and minimum drag. This takes a much longer
scoop throat than you have. The air entering will trip to turbulent
at the abrupt corner behind the B.L dam. This will result in poor
flow and pressure distribution, with most of the air going toward the
back of the scoop. I don t know what happens in your installation
downstream from the actual scoop, but you might consider some internal
baffles but get a more uniform distribution if the rad is close to the
scoop.
The boundary layer dam that you have is high
drag, and may be close enough to the entrance lip that backup of the B.L.
flow will be ingested into the scoop or it could result in some external
diffusion (pressure recovery) and allow the scoop to work just
fine. The idea in the B.L. bleed is to try to divert that flow
somewhere else, generally off to the sides. That would
require a much more gradual diverter angle.
I made a much more gradual bend in the wall
of my scoop (pic) attached. Still, in doing flow tests, I found
flow separation and turbulence which lead uneven flow distribution.
I added to baffles in the scoop get it fairly uniform. It could be
that some of the turbulence was a result of the test rig setup, although
I thought I had a long enough duct from the blower to straighten things
out.
The squared off internal corners will add
frictional drag, but probably not significant in overall picture.
But, hey try it. If it gives you the cooling
you need, you ve got 90% of the battle won. If you feel you need to
reduce drag, you can consider that at your leisure.
Al
Ed, and others -
Attached are some photos of the new scoop I'm building to
replace my old new
scoop. As you can see the new one actually has less
intake area, but
extends further in order to get outside of the boundary
layer.
I don't want the intake any larger than it has to be, but I
want to make
sure also that it is sufficient to allow for enough air
flow. My old new
scoop did improve cooling, but as I found out, it was only
marginal.
The new scoop, which is patterned after a P51 style scoop,
not only gets
outside of the boundary layer air, but also excludes it,
with the dam that
you see at the bottom. Well, actually it will be at
the top, once it is
mounted under the belly. It also gives me an expansion
area once inside the
scoop.
Using the program that Al sent me, the boundary area
calculated out to about
1.625-1.75 inches +/- depending on speed.
The scoop intake measures 10.75" inside at the top
(narrowest) and 14.75" at
the widest point average = 12.75"
Height of the inside of the scoop measures 4.25"
This should equal about 54.18 sq in of area.
The inside of the scoop sits exactly 2" from the bottom
of the fuselage, and
overall height to the outside of the scoop is about
6.6" again, measured
from the fuselage bottom.
I haven't glassed the scoop yet, other than on one side to
help with gluing
it together.
I am interested in any feedback concerning the size of the
intake area.
Regards,
Steve Brooks
Cozy MKIV N75CZ
Turbo Rotary
>> Homepage:
http://www.flyrotary.com/
>> Archive:
http://lancaironline.net/lists/flyrotary/List.html
|
|