|
|
If I understand it correctly, the 'bluff body', detailed in the CAFE articles I referred to earlier, does essentially the same thing; the bump accelerates the airflow & it (the bluff body) is sheared near the point of highest air speed. That creates a low pressure area for the cowl air to exit into.
I still think that if the tortured path of the air after it leaves the heat exchanger is straightened & cleaned up, that would make a lot more difference. (exit duct on the *side* of the cowl, exiting into the low pressure area near/above the wing's leading edge??)
Ed Anderson wrote:
IF the VGs are generating a vortex and are placed the right distance apart, closely spaced spinning vortex of air mass may act as an extension of a cowl flap area by preventing/hindering the higher pressure/velocity external flow from equalizing the pressure as soon.
Just an opinion (and that is about all it is) about why a set of VG MIGHT give some benefit.
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW <http://members.cox.net/rogersda/rotary/configs.htm>
http://www.rotaryaviation.com/Rotorhead%20Truth.htm
------------------------------------------------------------------------
*From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] *On Behalf Of *Mike Wills
*Sent:* Sunday, September 20, 2009 12:01 PM
*To:* Rotary motors in aircraft
*Subject:* [FlyRotary] Re: Another mixed day / Cooling experiments
I'm with you on the VGs. If your cowl flap didnt create enough negative pressure to acheive the desired results I dont see VGs being more effective. I dont recall ever seeing VGs used on any sort of factory built airplane for this sort of problem and I'd think if it were that simple the manufacturers would be doing it.
Mike Wills
RV-4 N144MW ----- Original Message -----
*From:* Tracy Crook <mailto:tracy@rotaryaviation.com>
*To:* Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
*Sent:* Sunday, September 20, 2009 6:03 AM
*Subject:* [FlyRotary] Re: Another mixed day / Cooling experiments
"It IS seeping from the filter seal and NOT the two hose
connections...no doubt on this. "
Just from observing many rotary installation 'de-bugings' over the
years (including my own) I noticed that difficult to solve
problems are almost always caused by false assumptions.
It is possible to get several bad filters or two bad filter mounts
but the mathematical odds are staggeringly small. You haven't
offered your test proofs as to why you know they are bad and
leaking but if I were betting, I'd put my money on something
else. The assumptions about the wiring might need examination as
well.
This reminds me of an oil leak the Ed Anderson had. The oil was
showing up on the back side of one of his rads. There was an oil
line running very close (< 1" as I recall) to the rad so the
assumption was made that the oil line was leaking. Long story
short, the oil leak was actually coming from something at the
opposite end of the engine. What exactly was it Ed? It defied
all logic in that it was not even close to where it showed up and
the oil was traveling against the assumed airflow under the cowl. Speaking of assumed airflow, my cooling experiments are blowing
away all my own assumptions. I kluged up the cowl flap I
mentioned and fixed it in the open position. The trailing edge of
outlet is about 1 1/2 " below where it was. The temperatures
were down a little but not near what I wanted. Only a little
better than the big giant opening I tried. At this point I was
ready to conclude that the underside of the airplane was bad place
to put a cooling outlet. Keep in mind that my working assumption
is that the pressure under the cowl is too high to allow good
airflow through radiator and oil cooler. I had installed a
pressure probe under the cowl but forgot to look at the reading. Figuring I might as well know how big a problem I had, I made
another flight to check the under cowl pressure. Duhh, almost
nothing! Checked the probe to make sure it was not blocked,
pinched, etc, and everything looked OK. I need to check pressure
in a few other spots to be sure about this. There is something
odd going on with airflow under the cowl but I'm back ti head
scratching mode again.
One builder on the RV list said he got a big improvement in
cooling by installing VGs on the trailing edge of the cooling
outlet. This is so non-intuitive that I can't imagine why it
would work but its so easy to try I might have to do it while
scratching my head.
Tracy
.
On Sun, Sep 20, 2009 at 1:37 AM, Chris Barber
<cbarber@bellairepolice.com <mailto:cbarber@bellairepolice.com>>
wrote:
Made it out to the hangar for most the day and decided to take the
advice here and modify my start up routine based on what was
suggested here and in the manual. So, I cranked the mixture full
rich with no priming and it started up in a few blades. Ran for a
while, shut down and started back up with mixture in about the
2:00 oclock position....and it started fine. Kewl.
The first bad news is that I replaced my romote oil filter mount
and installed a new filter. As I have mentioned here I have had
it leaking at the rubber filter seal. The old one looked ok, but
since replacing the filters no less than three times and knowing
that the eye cannot see all inperfections, I replaced the mount
AND filter (K&N 2004 filter). But, NO JOY. It is still leaking
where the filter mounts. It IS seeping from the filter seal and
NOT the two hose connections...no doubt on this. I know the
rotary's oil pressure is higher than other engines but I would not
think it would be so much that it is overwhelming this standard
mount and seal. This is just a standard screw on remote oil mount
made out of AL...Made in the USA. Looks like many others I have
seen. Y'all have any ideas.
Second good thing is a guy from a few hangars down turns out to be
a welder by trade. He came down as I was working on the new
stainless turbo exhaust manifold the other day after offering to
help me modify my manifold.. As was mentioned here before, the
old cast iron manifold I had wold work if mounted upside down. It
puts the turbo lower (the oil return being about 2 inches higher
than the oil inlet return in the pan) to the rear of the engine
and it clears my aileron control link. I will have to make a very
small modification to the lower cowl to give me proper clearance
EXCEPT the wastegate interfeared with the Mistral intake fuel
rail. So, I ordered a stainless copy of the cast iron one I had,
based on John Slades suggestion. My welder friend said it would
not be too big a job to turn the wastgate extension around which
should allow it to miss the fuel rail completly. We looked at the
options and he took the manifold with him saying he would cut off
the old wastgate extention and come back to fit the new part on in
a few days. Kewl.
The second bad news is that I was doing some continued tuning. I
even transferred A to B as B was a bit rough from the factory and
it worked fine. HOWEVER, later in the day, after feeling pretty
good about the lasted progress (excepting the continued leak) the
engine stopped. Huh? It will not restart. I checke the first
fuel filter and it is clear. I decided to start at the beginning
and just run the EC2's diagnostice test. Damn, no chattering of
the injectors (even though I was able to hear an individual click
when I primed it). Put on a test plug and wire and got no spark. All the other electrics are working fine.
I pulled my extra EC2 out and installed it and I got injector
clattering away and spark on three of the inectors. The secondary
on Rotor one did not seem to fire. Hmmmmm? I put on an extra
injector that I had and tried again, and it didn't fire...then
fired for a few seconds and then stopped. Looks like I have some
more wire issues. Damn, I though I had really gotten past most of
those.
I am really confused about the EC2 seeming to just shut down. The
other electrical componants are all working, but the EC2
componants are not. Strange since I thought each items (injectors
and coils) had there own power source thus should not shut down as
a "team" like this. Yes, it is the same on A and B. Currently I
am very discouraged so I stopped for the night and decided to
crawl into bed with a hot blond and sulk (she was actually
gracious enough to hang out in the hangar with me for a few
hours...whata gal)....well, she helps me from sulking too
much.....this dating in my 40's ain't all that bad <g>
I anxiously wait commentary and possible explanations from y'all. Upon my return to the hangar (today was MY Sunday) hopefully
tomorrow night after work I will be looking at my, apparntly piss
poor, wiring.
As always my friends, Thanks.
All the best,
Chris Barber
Houston
Warning: This e-mail transmission, and any documents, files or
previous e-mails attached to it, may contain confidential
information that is legally privileged. If you are not the
intended recipient or the person responsible for delivering it to
the intended recipient, you are hereby notified that any
disclosure, copying, distribution or use of any of the information
contained in or attached to this transmission is STRICTLY
PROHIBITED. If you have received this transmission in error,
please immediately notify us by telephone at 713-662-8132 and
destroy the original transmission and its attachments without
reading them. Thank you.
__________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________
The message was checked by ESET NOD32 Antivirus.
http://www.eset.com
|
|