REFLECTOR: ram air vs filter
John Tvedte
johnt at comp-sol.com
Fri Jun 15 13:17:25 CDT 2007
Jack,
Do you have static MP values of the ram air vs. filtered air - vs. ambient?
Also - what model of engine do you have? Any mods - higher compression, etc?
Any pictures of your scoop?
John
________________________________
From: reflector-bounces at tvbf.org on behalf of Jack Sheehan
Sent: Fri 6/15/2007 10:06 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: ram air vs filter
I have had very good performance with the alternate air system from airflow performance http://www.airflowperformance.com/. I actually use it differently. The photo is looking up at the engine the straight tube ( without the filter has the butterfly valve controled by a cable. In the open position the induction air comes thru the air scoop under the belly through scat tube making a S bend up to the fuel controller. This provides Ram air. If the environment is bad ie dust rain sleet etc (ground operations), I close the ram air and induction air is thru the K&N filter. The K&N is a RU-2790
There is almost 1 inch difference in manifold pressure due to the Ram air. Take off on the filtered air or unfiltered(ram ) is essentially the same since the effect of ram at slow airspeed is very little.. I thought the increased temperature of using air from within the engine compartment would cause an issue but it has not. The idea was to keep the filter protected from the elements so it would not clog due to ice dirt etc.
the air scoop I used was one velocity sells it was a mold used under the wings of older models.
Jack
N55XL
Race 55
At 10:14 AM 6/15/2007, you wrote:
Scott,
Yep, my air intake does take a turn over 90 degrees and I will have some measure of disturbed flow in there. It is a compromise design like so much of this is. I am not sure we need a ram air. The engine intake will suck air sufficiently, hopefully, thru that turnit is shortest distance I can make it with a pretty straight run after that. We are talking a short distance. I know airliners are not a good comparison, but I did have these jet experiences that I included (best I recall) as Collier and I discussed the issue. The B-727 center engine is actually in line with the two pod engines thru a big S duct. I was unheard of at the time. Compressor stalls were is big issue on start up or even on the ground when I guy would make a rolling takeoff in a big crosswind the pour the coals to it with inlet air all disturbed. It took some testing in the early development years but it works. Douglas, in the DC-10, rejected it in its bigger trijet, while Lockheed in the L-1011 included it.
Of course cylinders sucking air are different than compressor blades which are more flow sensitive. I opted for what we did. My thinking for anybody not up to this point could include these points: I saw Chuck Jensen's intake. He uses a portion of what would be cooling air by ducting out of his roof NACA's. (And his intake ducting took some big turns too, and didn't have a lot of ram quality to it per se.) He never mentioned any oil temp/cooling issues that I recall. I think a good hunk of that approach would have to include a good cooling plenum. I never asked him about this, but I am glad myself to have the space free for other stuff in the engine-block-to-firewall real estate. Lots of stuff has to go there.
Belly intakes maybe like Rene would be the best for ram air advantage. His has worked too, based on his 500 hours. I would worry about sucking in water/slush kicked back from the nose tire. That was a problem in the later stretched versions of the DC-9. In fact they put mud flaps on the nose tire. For us...well we are not all weather operators. Personally, I would, and I bet most others would delay a takeoff or landing if there was active moderate precip that could otherwise be avoided for lots of reasons other than intake debris. Just my 2 cents. Oh, and thanks. I guess it is a K&N filter not K&M.
Terry
________________________________
From: reflector-bounces at tvbf.org [ mailto:reflector-bounces at tvbf.org <mailto:reflector-bounces at tvbf.org> ] On Behalf Of Scott Derrick
Sent: Thursday, June 14, 2007 9:34 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: ram air vs filter
Terry,
are you blowing air backwards through the K&N? Does it matter which way the air flows. into the cone or out of the cone?
Scott
Terry Miles wrote:
Keith,
Here's what I got...mostly
this is a Malcolm Collier/Hangar 18 effort.
He
did the actual carving, and
it was his idea. I took it from there. I
can
send more pics if you need
them. It is the carved foam block routine.
Note
the scoop is away from the
underside of the wing, and you can see the
outlet
duct going into what would
be the eng compartment. We will use a short
hunk
of hose to connect.
The wing root section fits the standard
size
rectangular K&M filter
and has the suction 2ndary door on a spring
for
filter
bypass.
The intake plenum that came
with the engine didn't work. Mine now goes
off
to the right at about 35
degrees (to the left if you talk to Don
George!)
He was good about swapping
out the straight on one we had to begin
with.
I've got the Ly 540.
I think there are 3 different
induction
chambers/plenums whatever
they are properly called. They come on and off
w/
a couple of
bolts.
Hope this inspires!
Good luck.
Regards,
Terry
-----Original
Message-----
From:
reflector-bounces at tvbf.org
[mailto:reflector-bounces at tvbf.org]
On
Behalf Of Keith
Hallsten
Sent: Tuesday, June 12,
2007 9:05 PM
To: 'Velocity Aircraft
Owners and Builders
list'
Subject: Re: REFLECTOR: ram
air vs filter
Rene',
This sounds like a pretty
practical set-up for induction. Do you have
any
pictures? Is the
"midline scoop" available, or was that a one-off
custom
part?
I am in the midst of engine
installation, and the induction system seems
to
be the part I'm having the
most trouble with. I have made a couple of
air
boxes using the "lost
foam" method, but found their design to
be
unsatisfactory. I'm
definitely looking for inspiration on
this.
Keith
Hallsten
XLFG, Roseville,
CA
-----Original
Message-----
From:
reflector-bounces at tvbf.org
[mailto:reflector-bounces at tvbf.org]
On
Behalf Of Rene
Dugas
Sent: Tuesday, June 12,
2007 4:22 PM
To: 'Velocity Aircraft
Owners and Builders
list'
Subject: Re: REFLECTOR: ram
air vs filter
I use the midline scoop
mounted to the lower cowl and the rear of
the
fire wall. I used a K
& N cone shaped filter mounted to a 3
inch
aluminum flange with an
identical flange mounted the opposite
direction
in a fiberglass box.
This is attached to the induction by 3 in.
scat
tubing to allow for
vibration. I mounted a spring operated door in
the
side of the box for
emergency air that sucks open if I close the
scoop.
I made the box by forming
foam and coating it with glass. I
used
acetone to dissolve the
foam and presto custom air box. I seem to get
1
to 2 inches of MP based on
side by side flights with others at
the
Velocity
Symposium.
My scoop starts out about
1.75 by 2.25 inches and opens up
into
approximately a one foot
square air box with the K & N in
it.
Just FYI. I can
remove the lower cowl and the scoop screws to the
box.
I can remove the two screws
in the scoop and remove the filter
for
cleaning.
Rene'
-----Original
Message-----
From:
reflector-bounces at tvbf.org
[mailto:reflector-bounces at tvbf.org]
On
Behalf Of
Tom
Sent: Thursday, June 07,
2007 8:01 PM
To:
reflector at tvbf.org
Subject: REFLECTOR: ram air
vs filter
My problem was that I went
from ram air to what was too small of a
filter. It was a 3"
diameter x 5" long. I clamped it directly to the
induction air tube. I
really need a larger filter with filtration on
the
end also (this was closed).
Very space limited under there as I share
the ram air inlet with a
2nd oil cooler mounted on the baffling. (large
aeroduct hose). I may just
go with a
screen.
_______________________________________________
To change your email
address, visit
http://www.tvbf.org/mailman/listinfo/reflector <http://www.tvbf.org/mailman/listinfo/reflector>
Visit the gallery!
www.tvbf.org/gallery
user:pw tvbf:jamaicangoose
Check new archives:
www.tvbf.org/pipermail
Check old archives:
http://www.tvbf.org/archives/velocity/maillist.html <http://www.tvbf.org/archives/velocity/maillist.html>
_______________________________________________
To change your email
address, visit
http://www.tvbf.org/mailman/listinfo/reflector <http://www.tvbf.org/mailman/listinfo/reflector>
Visit the gallery!
www.tvbf.org/gallery
user:pw tvbf:jamaicangoose
Check new archives:
www.tvbf.org/pipermail
Check old archives:
http://www.tvbf.org/archives/velocity/maillist.html <http://www.tvbf.org/archives/velocity/maillist.html>
_______________________________________________
To change your email
address, visit
http://www.tvbf.org/mailman/listinfo/reflector <http://www.tvbf.org/mailman/listinfo/reflector>
Visit the gallery!
www.tvbf.org/gallery
user:pw tvbf:jamaicangoose
Check new archives:
www.tvbf.org/pipermail
Check old archives:
http://www.tvbf.org/archives/velocity/maillist.html <http://www.tvbf.org/archives/velocity/maillist.html>
[]<http://mail.comp-sol.com/exchange/johnt/Drafts/7.0.1.0.1.20070615104512.02313350@ncam-sats.org.1>
_______________________________________________
To change your email
address, visit
http://www.tvbf.org/mailman/listinfo/reflector <http://www.tvbf.org/mailman/listinfo/reflector>
Visit the gallery!
www.tvbf.org/gallery
user:pw tvbf:jamaicangoose
Check new archives:
www.tvbf.org/pipermail
Check old archives:
http://www.tvbf.org/archives/velocity/maillist.html <http://www.tvbf.org/archives/velocity/maillist.html>
--
-
The only
security of all is in a free press. The force of public opinion cannot be
resisted when permitted freely to be expressed. The agitation it produces
must be submitted to. It is necessary, to keep the waters
pure.
Thomas
Jefferson to Lafayette, 1823. ME 15:491
_______________________________________________
To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
Visit the gallery! www.tvbf.org/gallery
user:pw Check new archives: www.tvbf.org/pipermail
Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/ms-tnef
Size: 22397 bytes
Desc: not available
Url : http://www.tvbf.org/mailman/private/reflector/attachments/20070615/177d1bde/attachment-0001.bin
More information about the Reflector
mailing list