A Focke Wulf 190D Dora had a real ram air scoop for its
Jumo 2000 HP 212E V12 engine. It also used ring radiators
inside the cowl with nice cowl flaps.
Paul Lamar
What do you think of the efficiency of the annular inlet (around the
spinner - as FW-190)
as compared to a conventional scoop? It seems to me it would have
higher drag than a
conventional scoop of the same effective area - more drag area... Same
thing for anular
exhaust on a pusher config. I find it interesting the FW got that
inlet. On a radial engine,
it makes sense, however.
Regards,
Matt-
Not according to Hoerner. Those are low drag numbers.
The big problem is making the ring radiators and the starter
interference.
Another problem is ground taxi cooling and climbing out at low speeds.
You will get more benefit from the prop slip stream if the intake
is further out from the hub.
Paul Lamar
As far as I understand the FW-190D model is just an evolution of the
previously BMW-radial engine powered models. I imagine that the
aerodynamically generally good configuration was taken over to the Junkers
Jumo-V12 powered version, so that there was no danger to loose time
developing a different cowl. At the time the D-model showed up the Germans
where already in trouble all over the fronts, so there was no time to be
lost. Fabricating round radiators was obviously no problem either.
I did not look into the reason for the ram-air intake, but I also would not
rule out a general lack of space inside the cowl.
Compare the Me-109 F, which was the smoothest and fastest version of all
Messerschmitt-109's. The 109-G got all kinds of bumps on the cowl because of
lack of space for additional equipment under the cowl - Stronger engine-
more coolingspace needed, bigger gun, etc.
It was more powerful, heavier, heavier armed, etc.
http://www.wpafb.af.mil/museum/air_power/ap14.htm (here is a reference to
both airplanes)
However looking at Mike Arnolds AR-5, http://www.ar-5.com/ : It is powered
by a 65HP 2-cyl, Rotax, but still uses a round cowling. He says researching
the subject points to this design as the aerodynamically most efficient -
least drag. No ram-air intake.
I believe this round/radial cowl would lend itself to propeller-augmented
ram-air cooling, .....(can't find it on the net, but you all saw these props
with a tap like extension of the prop chord, at the root of the prop - just
in front of the air intakes....)
In comparrison to the regular check cowls where these props are used, the
round cowl would have the advantage of 360 deg augmentation, not just in the
short time the prop passes the checks.
A different approach would be a fan, driven by the propshaft at prop speed.
Here an excerpt from the Flugwerke website, about their FW-190:
- - - - - -
The cooling fan is an operational unit which sports ground-adjustable
blades. By changing the incidence of the fan-blades, the cooling system can
receive a basic adjustment in order to cater for different climates in which
the a/c will be flown and thus increase efficiency. The fan turns at the
propeller rotational speed and is integrated into the spinner's back-plate.
- - - - - -
Thomas J.
PS: Anyone interested in a new "production" - version of a FW-190, with
authentic continued production number, issued from Focke-Wulf?
see http://www.flugwerk.de/ ....however that's the Radial engine powered
version....with a Russian engine.
I am not sure about that. As you can see the V12 was mounted far back from the
propellor. I think it stemmed from a desire to reduce the cooling drag and have
what was referred to as a "power egg". CG considerations would not make the engines
interchangeable firewall forward.
Paul Lamar
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