Tracy Crook wrote:
Yes, the airstream is split horizontally as Ed speculated. It is
interesting to note that the airfoil shaped splitter was Very critical.
When I tried just letting the air spill over the top of the water cooler to
the oil cooler, it didn't work worth beans. This is another indication that
there is high speed airflow internal to the inlet. The right side
nostril was enlarged (on top) in an effort to improve oil cooling before the
splitter was installed. Enlarging did not help but I have not had the time
to un-do the grotesque nose job. Note that the lower portion of inlet area
on the right side which feeds the water cooler is only 9.5 X 1.5 inches.
Thats only 14.25 sq. inches. The close-up photo and Pauls comments make it
sound huge. The radius of the top & right side of the right inlet is way
less than needed to streamline the airflow over it and is generating
unnecessary drag. Don't copy this.
Another point to make is that the left side inlet also served as the
carburetor air inlet (before I switched to EFI). I will admit that cooling
improved quite a bit when I stopped robbing air from this inlet to feed the
engine. Even at that, the dimensions are 7.5 X 3.25, about 25 square inches.
This isn't all that big but it's bigger than it needs to be now that it does
not feed the intake system. It will take someone with better aerodynamic
chops than myself to prove it but I'm still betting that this is primarily
an internal diffusion system (albeit, a less than optimized one).
And while we are betting, in this kind of cooling system (engine behind
radiators), it is a waste of energy to ventilate the engine compartment with
"outside" air. I've seen this done on a dozen airplanes but it's still a
mistake.
Tracy, Jeff and I were only advocating that *IF* you had a sealed exit
duct leading from the back side of the rads. PL
1. The air on the backside of the radiator is still cooler than the engine
and ----
Got any numbers on that Tracy? The exit air temperature, as Jeff pointed
out, is a measure of the cooling system efficiency. PL
2. Any air you duct into this area will raise the pressure behind the
radiator thus reducing airflow and cooling.
The only exception to this is for very small amounts of air for cooling the
alternator and ignition coils. This is best done via "blast tubes".
BTW Paul, no need to apologize for showing my "less than beautiful" air
inlets. Hell, I've flown it to Oshkosh for the past 4 years and stuck a
Judge Me sticker on the prop sign. Not that I ever expected to win. The
award for technical innovation (can't remember the official name they give
it) always goes to a gorgeous paint job. Same story for the Best Auto
Engine Powered award. Last year it went to a VW powered KR2 which was block
stock except for a magneto hung on it. The tech award in 97 went to another
KR2 with a turbine APU engine installed. It didn't perform any better than
the VW powered KRs but it did drink 16 GPH at cruise. Great progress.
;-)
OK, enough of my sour grapes.
First test stand results on the composite (upper half) intake manifold were
run last week with good results. Didn't really prove much yet except that
power at 5500 rpm was essentially the same as my aluminum job which has 12
inch longer runners. This is based on reference data gathered during prior
tests and fuel flow readings. The only disappointment was that I could not
test at 6000 - 7000 rpm where it should work the best due to prop load
limitations. I'm in search of a smaller prop that will allow higher rpm.
Testing was halted when the engine backfired on startup (a very rare
occurrence on a rotary. How this can happen is a long story) and the
fiberglass manifold blew apart and the throttle body fell off. OOPS,
something to consider! Nice thing about EFI is that if this somehow
happened in-flight (not possible unless things are terribly wrong) the
engine would not stop but would go to full power! Damage was minor so I'm
going to glue it back together and try again.
Tracy Crook rws@altavista.net
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