Paul is correct - when I say jets, I mean straght turbojets - where all

the

air
goes thru the combustion chamber, and they are indeed near extinct. I
certainly did not say turbines stink and you are right that big bucks,

big

HP gas turbines are running really great specifics actually better than
Diesels on some points - and they do not scale worth beans to small
size and low cost. High bypass turbofans are often below 0.4 TSFC
(at static - they get poorer at speed) actually the TSFC static
for a Cessna 172 is probably about 0.15 also getting poorer with
speed. Turbofans are probably the best examples of the big mass,
lower velocity school. Those fans are running air slower than
flight speed to keep the blades well subsonic - raising the total
pressure of the downstream flow, and expanding up in velocity
in a contracting exit cone. Sound absorbing wall structure typically
fore and aft to be quieter. Those ducts are good for high power
fast, and the ducts we have been discussing are good for slow
(and safety on the blimps) and between it is rocky desert, where
a good prop is the best compromise - Vance

Vance,

Don't forget the gains that the transonic fan made possible. Otherwise you
have to go to a geared fan....again...yuck. We are of course comparing TSFC
and BSFC numbers. The real deal is seat mpg. Going fast and high really
helps in that regard, as does the airframe design.

I really do think that an efficient turbine in the 100-200 shp range is
possible. The only thing it will require is doing things differently. It is
now possible to get pressure ratios in the 4-5 range with a single radial
compressor with efficiencies in the .8 range. Also single stage radial
inflow turbines in the .85 efficiency range. These things are tiny by piston
engine standards. The only thing missing is a recuperator. Should be plenty
of room under the cowl for that. Alas my development budget is limited, and
NASA is off chasing rainbows, while Williams is not interested in our
market.

Monty

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