Joseph M Berki wrote:

Perry,
       How is the search for the ultimate oil cooling system

going?  Charlie

Airesman and I are having a discussion about moving radiator and oil

cooler

to the strake wing close outs.  I am concerned about drawing air in

from an

armpit and exhausting out the upper trailing edge much like your oil
cooler.  Is that area a true low pressure area?  Thanks for any help.

Joe Berki
Limo EZ

Joe:

The short answer is yes, it does seem to be a low pressure area. But I'm
not sure how much of the effect is due to the ductfan in my case. It
might be worth your while to take some pressure measurements on a LEZ or
VEZ with a conventional prop.

I think it makes more sense to draw air in the armpit, a high pressure
area, and exit on top in the lower pressure area than to do it the other
way (downdraft). When I had the big louvres in the top of the cowl above
the oil cooler, I was relying on the natural low pressure area on top,
and did have a pressure drop across the oil cooler and airflow through
it in the correct direction. When Paul was here with the water
manometer, we added an exit duct that put the exit of the duct close to
the fan. This definitely increased the suction from the rear, but the
pressure drop didn't increase much because the suction carried forward
to the inlet side, lowering the pressure in the inlet. I also didn't
notice much change in oil temp with the mod because the pressure drop
across the cooler didn't really increase much. I thought about making
the inlet larger to try to get more pressure back on the inlet and
hopefully develop a larger pressure drop, but haven't done it yet. I'm
not sure I want to make the inlet any larger, it is already 5 x 5 inches.

I think with a prop farther to the rear than my fan, which yours would
be, and no fan duct that extends forward a foot in front of the fan, you
would not get the big suction from the rear that I do. But I think that
is not really necessary. The big advantage of the big rear suction of
the ducted fan is mainly for ground cooling, but it could also be
helping a little in climb. If I take the fan duct off and let the engine
idle on the ground it will eventually overheat. With the fanduct in
place it can idle all day and the engine will hardly warm up.

--
Perry Mick
Custom Composite Props
mick@bridgingworlds.com
http://www.ductedfan.com

-Joseph Berki wrote:

Perry,
         Have you oil flow tested the inlet?

Joe- 

 
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