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Great to hear, Tracy.
All of the studies I have read indicates
anything you can do to prevent flow separation near the inlet (which you
undoubtedly had at anything off straight and level with those tubes) greatly
aids cooling.
The studies say that anytime you have a
disturbed/(turbulent) area of air impinging on an area of your radiator face you
do not get good pressure recovery from disturbed air - this in turn can
cause that area impacted to suffer a 20% degradation of cooling
effectiveness and also increased drag. The further upstream from
the core the disturbance occurs the larger the affected area of the
core.
So your enhanced pressure recovery with the new inlets is
likely largely due to the better control of the entering airflow and the
reduction of any separation caused by the sharp ages of the tubes.
Also looks great. I noticed the inlets appears to have a
removable cover -- I presume this is so you can remove the inlet
cover in order to remove the cowl (or for further experimentation
{:>)?)
Ed
Sent: Thursday, April 28, 2011 9:07 AM
Subject: [FlyRotary] Re: Cooling Inlets
Finally got
around to finishing my cooling inlets. (pictures attached) Up until now
they were simply round pipes sticking out of the cowl. The pipes are
still there but they have properly shaped bellmouths on them. The
shape and contours were derived from a NASA contractor report (NASA_CR3485) that
you can find via Google. Lots of math & formulas in it but I just
copied the best performing inlet picture of the contour. Apparently
there is an optimum radius for the inner and outer lip of the inlet.
There was no change to the inlet diameters of 5.25" on water cooler and 4.75" on
oil cooler.
The simple pipes performed adequately in level flight at
moderate cruise settings even on hot days but oil temps would quickly hit
redline at high power level flight and in climb.
The significant
change with the new inlet shape is that they appear to capture off-axis air
flow (like in climb and swirling flow induced by prop at high
power) MUCH better than the simple pipes. First flight test
was on a 94 deg. F day and I could not get the oil temp above 200 degrees in a
max power climb. They may have gone higher if the air temperature
remained constant but at 3500 fpm the rapidly decreasing OAT kept the temps well
under redline (210 deg F).
I have an air pressure instrument reading the
pressure in front of the oil cooler and was amazed at the pressure recovered
from the prop wash. At 130 MPH the pressure would almost double when the
throttle was advanced to WOT. That did not happen nearly as much with the
simple pipes.
These inlets ROCK!
Tracy
Crook
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