Tracy,
Wow! That is less than 40 sq in of inlet
area! Total!! How much exit area do you have?
You mentioned a pressure sensor. What pressures
are you seeing at wherever you measure it?
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Tracy
Sent: Thursday, April 28, 2011
9:08 AM
To: Rotary
motors in aircraft
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