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Not sure where you are going from what I read. Are you suggesting that a turbo could be used as a source of cooling air? Hmmm..... a novel approach but the design of the usual turbo would be all wrong in terms of pressure ratio and volume. Would require a new design I think. The volume of cooling air for a typical 200 HP installation is on the order of 3000 CFM.
You obviously know more than I about turbine engines. I had no idea that compressor bypass air was used for cooling. I thought is was for thrust. I'm sure it is in the larger high bypass ratio designs (like on 747, etc)
Tracy
On Thu, Jan 26, 2012 at 11:27 PM, Mark McClure <markmcclure@me.com> wrote:
Ok bare with me here, I have been digging through all my old engineering books trying to answer this but have come to no intelligent answer.
I work behind turbines a lot and they are wonderful when they are needed - but the fuel guzzling just makes them ill suited for our needs - enter the rotary. But in designing my engine I am curious about using some theories from the turbine.
For this reference I am using a 420hp C-20J Turboprop (just because it is the smallest I have used)
Approximately 70% of the energy is used to turn the compressor and accessories and 30% is used for actually turning the output shaft. Of that compressed air only 25% is used in combustion while the remaining 75% is routed around the combustion chamber for cooling.
The compressor is a six stage axial, single stage centrifugal. Compressing the air 6.5 times and the temperature is about 500F. The TOT (also TGT or ITT, measured between the gas turbine and power turbine) is 1500F.
The 13b MSP is putting out exhaust temps of 1600F. So using the same principles in reverse, the remaining energy powers a compressor (turbo) and that air is then used to assist in the cooling.
So the question is: What have I oversimplified?
Mark
Glasair SII - 30% complete
13b MSP - 5% complete
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