REFLECTOR: Innodyn Engine

[Richard Riley]

At 07:36 PM 4/5/2006, you wrote:

>As far as I know there is no turbine or jet engine that comes close 
>to the BSFC of a piston at sea level.  If they could do this, then 
>they would be very rich.
>
>Now, if this thing happens to get to someone with a non-biased 
>interest and posts that their numbers are true, then I'll retract this comment.

Actually, there are turbines that are better than pistons for BSFC, 
but they're a little large for our use.  It all comes down to 
compression ratio. and cooling.  An intermittent combustion engine, 
like a piston, gives the combustion chamber elements some time to 
cool between combustions, and keeps the temperatures comparatively 
low.  Your piston engine is running somewhere between 5 and 15 to 
1.  Standard Lycomings are 8.5:1, I'm running high compression 
pistons at 10:1, some hot rod cars are as high as 15:1.

The GE-90 on the Boeing 777 runs at 45:1.  The air goes through a 4 
stage low speed axial compressor and a 9 stage high speed axial 
compressor.  It runs a BSFC of .306, about as good as a very large 
(ship size) diesel.  Before the air is mixed with fuel it's at 661 
PSI, and is very hot.  After combustion the gas is cooled down with 
dilution air to 2700F, before it gets to the high pressure 
turbine.   Of course, it 78,000 horsepower.

The closest production turbine for this kind of use is the Allison/RR 
250.  The C18 runs 317 HP, a six stage axial, 1 stage centrifugal 
compressor at 6.2:1, but a BSFC of .7.   The next is the PT6 - 850 
horsepower, three stage axial, single stage centrifugal, 7:1 
compression ratio,  and a BSFC of .69

Yes, there is a pattern developing here.

In one set of numbers I find Innodyn is claiming about 7 gph/100 
hp.  Jet fuel is 6.4 lb/gal, so that's a BSFC of .45, about the same 
as a Lycoming piston engine.  But they're claiming it with a single 
stage centrifugal compressor and a 4.5:1 compression ratio.  That's 
is better than the Solar T-62 that it's based on, which ran 3.5:1.

So, as far as Innodyn's fuel burn claims are concerned, I agree with you.