Paul McAllister a crit :
> One jug we set up a
> swirl action and compared the time to the jug that just "glugged
> away"... the swirling action was much faster.
>
> So, I was wondering if on your inlet if you could encourage the air to
> spin a little if you would stop the pressure wave, and possibly get
> more air into the inlet.
>
Paul and all,
The swirl is for letting water out and air in at the same time.
Hopefully in a cooling duct there is a way out for the air !
The laws of engine or radiator aerodynamics are now well established.
You need a well designed inlet and diffuser at a location when air is
not too disturbed and you can take advantage of its velocity to convert
most of the dynamic pressure into static pressure.
Behind the engine you need a convenient exit with a converging duct to
convert the remaining pressure into velocity so that drag is as limited
as possible.
"The lip" often seen at the exit doesn't help much if the inlet is
misplaced or wrongly shaped.
Concerning the Jabiru, there is little room between the prop and the
front cylinders to provide a correct diffuser, so the inlet must be of
larger size, and the efficiency will be lower.
But the engine can be adequately cooled all the same, at the price of a
little more drag, of course.
Some info on a well cooled Jab cowling and principles of cooling at :
http://contrails.free.fr/diap/phpslideshow.php?directory=diapo_capot_rt
http://contrails.free.fr/engine_aerodyn_radia_en.php
http://contrails.free.fr/engine_air_inlets.php
FWIW,
Best regards,
--
Gilles
http://contrails.free.fr
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