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Hi Doug,
No doubt when you have different (higher?) standards they can be tougher to
meet {:>).
I agree with you assessment about a "reverse venturi" duct. I
have a larger "capture area" before the one duct necks down to 10 sq inches and
the other to 18 sq inches. My theory was that would increase the velocity
(dynamic pressure potential) to help maintain that higher dome of pressure in
front of the core that my radical curved duct walls infringe on. My inlet
is 6" long on one side and 3" long on the other, so did not have a lot of room
to play duct with.
I flew a max power/climb take off two days ago with the ground OAT was 85F,
by the time I hit 3000 MSL the oil temp was up to 210F and the coolant to 220F
(my personal maxs for short duration). I then leveled off and let the
cooling system catch up with heat load. So it does appear that for mid
summer operation a bit more inlet area is called for. I intend to open up
the 10sq inch side (which is on my hottest radiator - first in the series) to 18
sq inches as well. That will provide a bit more margin on those hottest
days. My personal experience with the 91 turbo block and the Teflon coat
silicon coolant "O" rings that even coolant temps of 240F for short periods do
not appear to have done any harm - as you say, coolant and combustion chamber
are still separate.
But, I am please with the experiment in that I believe for my HP engine (I
estimate 175-180HP) I have found a "lower" limit on duct size. Although
perhaps with "exhaust augmentation" it could be made to work fine in hotter days
- much easier just to open one duct up a bit.
I total agree, when approaching trees or a ridge line - who cares about the
temps - can always replace the engine (if necessary) provided you clear the tree
line.
It always a personal pleasure to exchange ideas, experiences and theories
with people of the calibrate we have on this list. I always report my
happenings - even when they are a bit embarrassing at times. I seem to
have had an unusually assortment of events happen. I was awarded the
Rotary Round Up "Lightening strikes six times (or more) award which lists a
litany of things from oil pump key drop out, front tire gauges on both sides by
the bolts holding on the wheel pant when I screwed them in a bit too much and
then planted the front tire a bit hard causing it to balloon out and catch the
bolts, flop tube drop off resulting in a 12 miles engine out glide, etc,
etc.
But one of the main reasons I share - is life is too short to make
all the mistakes yourself, so my objective is IF you are going to make mistakes
- advance the state of the art and make one I haven't - we already know how
those turned out{:>).
Thanks for the comments, Doug. We try our best - and what's great is
when you're wrong, folks will bring it to you attention - in a pleasant
manner.
Tomorrow I launch (weather permitting) heading down to join Tracy Crook and
on to Lakeland, Fl for Sun & Fun hope to see a bunch of your folks down
there.
Best Regards
Ed
----- Original Message -----
Sent: Friday, April 08, 2005 11:05
AM
Subject: [FlyRotary] Ed Anderson Cooling
System
There were those who claimed that there was no
way that would work. Well, I reduced my inlet area from 48 sq inch to
28 and it works just fine thank you. Tracy Crook can vouch that I have
flown with the small openings for well over a year and he has never seen
steam or smoke coming from my engine - yet
{:>).
Hey Ed...that was probably me! All my analysis uses Military Air
outside conditions (+40 deg F over standard conditions), are climbing at
100 mph TAS (near max rate of climb) and assumes that you are actually
generating 200 HP. At 2,000 ASL and +40 deg F over
standard....I suspect you are not generating 200HP and if you are indeed
capable of 200 HP probably do not maintain that operating condition
sufficiently long (at 100 mph) to reach steady state conditions which my
rules of thumb consider.
Hopefully if you ever are approaching the trees on T/O under the
more severe conditions you can tolerate 245+ deg F engine out coolant
temperature. Been there done that with the Mooney. You know
what? The throttle stayed in WOT and no leaves on the belly! It
defined "pucker" for me. So you'll have to forgive me if I size my
inlets just a little bit larger for our 95 deg summer days. (Military
Air at sea level is 99 deg F)...WOT...generating 200 HP for an extended
period!! Do what Tracy "noodles" and spray water on the heat
exchangers!! Of course you have to carry that two gallons of water
around for the inevitable situation :>). Sort of like a "gear
up...not if, but when...if one flys enough.
Incidentally we unavoidably reached those 245 deg F engine out
temperatures while developing my friends system without "apparent" ill
effects. He does not have sufficient hours to determine if there were
long term effects, but water and oil are still separate! Being a
little experienced with automotive tests I would estimate that short of rapid
temperature "shock" at those temperatues, no damage was done.
Note: one of the OEM Automotive tests of heads/head gaskets is to dump
just above freezing water into the engine inlet side of the waterpump while
running at full tilt!! That is thermal stress!
SWAG (valuable engineering tool), I believe you have what is almost a
reverse venturi duct and your "effective" inlet area is actually larger than
28 sq. in. which is probably your smallest area in the inlet duct. I
have "noodled" (another valuable engineering tool!) that what you are doing
might very effectively compensate for a very short inlet duct....but
probably is a small detriment to cooling drag. Too small to matter
IMO.
Hey, you are a terrific experimenter and an invaluable Hummmmmer flyer
who is willing to share even at the risk of us "still building" asking
questions trying to understand what is happening in the Big RW. It
is terrific you share so we can consider what you have done and if we are
smart....will try to implement same in our own builds.
I truly appreciate your combination of theory, practical application and
ability to write!! Thanks!
Doug in CO
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