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


Paul Lamar

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