Paul,
Have you seen any development, theoretical or practical, of the
following:
Aircraft have a unique opportunity for using a compounding turbine's
shaft energy. The cooling drag for an aircraft engine is about
equal to
the energy recovery from turbo compounding. Both are 10-15% of the
power
output. Connecting an exhausting fan directly to the recovery turbine's
shaft could push the cooling air from the cowling at free stream
velocity or greater.
When the outlet velocity matches the inlet, cooling drag vanishes.
The simplicity of a lightweight volute or shroud and an exhaust pipe
could replace the complexity, weight, cost, and potential problems of a
gear train and its safeguarding mechanisms.
Thanks,
Philip Groelz
That is a real good idea Philip.
Here is something similar.
Paul Lamar ...No rotor no motor.
This is an interesting idea and I have thought about it alot in the
last
few days. What I can't figure out is how to get the blower or sucker
under the cowl. Too big.
Then I thought well why not use an exhaust ejector AKA augmenter to
evacuate the cowl and reduce the cooling drag. This too uses the waste
energy in the exhaust to reduce the cooling drag.
Nothing new here. The high velocity exhaust gases entrains air and
sucks it out of the cowl. This is a direct way of utilizing the
waste energy in the exhaust. Here are a couple of 3Ds. Main problem
is it adds to the frontal area and therefore increase the drag on a
tractor airplane. Probably will work fine on a pusher to reduce the
drag. At least one pusher rotary is flying with an exhaust ejector and
Charlie Airseman flew his Subaru powered Variez for a few years with
one.
Here are some old NACA papers on the subject.
http://naca.larc.nasa.gov/index.cgi?method=simple
1. An experimental investigation of rectangular exhaust-gas ejectors
applicable for engine cooling Manganiello, Eugene J Bogatsky, Donald ,
NACA Aircraft Engine Research Laboratory (Cleveland, Ohio., United
States)
NACA Report 818, 19 pp.
2. Preliminary investigation of cooling-air ejector performance at
pressure
ratios from 1 to 10 Ellis, C. W. , Hollister, D. P. , Sargent, A.
F., Jr. ,
Lewis Flight Propulsion Laboratory, Cleveland, Ohio. NACA Research
Memorandum
E51H21, 23 pp. , 1951
3. Preliminary air-flow and thrust calibrations of several conical
cooling-air
ejectors with a primary to secondary temperature ratio of 1.0 I
:diameter
ratios of 1.21 and 1.10 Greathouse, W. K. , Hollister, D. P. , Lewis
Flight
Propulsion Laboratory, Cleveland, Ohio. NACA Research Memorandum
E52E21, 26 pp. , 1952
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I was guessing that an exhaust turbine driven exhaust fan
combination would only be slightly larger than a typical
turbocharger. I have to admit, however, that I'm very much in the
market for a copy of "Turbomachinery for Dummies."
My understanding is that the augmenter systems tend to increase the
exhaust noise level. We were at a race track several years ago
where a Mazda powered car was competing. After pulling his fingers
following one of its passes, my friend said "I think that makes
about as much noise as it is possible for an internal combustion
engine to make."
You seem to have found a muffler design that offers some hope for
"taming the beast." Unfortunately I haven't been able to listen to
it yet. And I have no idea how it would work with an augmenter.
Cessna used the augmenter design with their early 310's and I think
they were relatively successful. I don't think they used it with
any of their later designs. I seem to recall that noise was one of
the reasons, but not the only one.
As a result I'm not ready to pursue the augmenter ideas at this time.
Philip Groelz
No doubt it is noiser than any muffler but we had a Velocity with
a p-port rotary and exhaust ejector at OSH this year and it was not
all that bad. Certainly not as bad as a P210 or AT6.
Megaphones on the other hand result in permanent hearing
damage instantanously :)
Paul Lamar ...No rotor no motor.
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