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Calculating thrust

Calculating thrust

Calculating thrust

(OP)
Calculating thrust of a bypass fan turban. I have a 31 blade fan that turns 8000 RPM, tip diameter 16 inches 8 inches of the root of the blade I'm trying to figure out how much thrust this fan will produce or some assistance in finding the math.

RE: Calculating thrust

Is this a hobby project or actual professional work? If it's work, perhaps there might be a better forum for a question like this. If it's a hobby, exactly what is it that you do in your spare time, build jet engines winky smile

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Calculating thrust

Measure the total pressure rise across the fan at that rpm. Then get a copy of Gordon C. Oates' book on Aerothermodynamics (ref. 1), the math is well explained in there.

If you don't actually "have" a fan to measure, then the math gets a bit hairier, and you will need the 2nd of Oates' books (ref. 2) where he discussed blade cascade analysis.

ref. 1 https://www.amazon.com/Aerothermodynamics-Turbine-...

ref. 2 https://www.amazon.com/Aerothermodynamics-Aircraft...

RE: Calculating thrust

(OP)
Strictly hobby, I'm just adding a ducted fan using the first stage of a Ge j-85 and want to make sure that it's going to put out enough thrust ( mathematically & theoretically) before I start annoying the neighbors again but they are entertained by the turbone.

RE: Calculating thrust

Oh man, you can't ask a question like that without telling us what this hobby project is. You've rung Pavilov's bell and now we're all drooling.

RE: Calculating thrust

Made me look it up.
The GE J85 is not a "small" engine.
Sounds fun - less the annoying neighbors that cannot see the "fun" in this project.

RE: Calculating thrust

I just hope he is not trying to put " THAT" in a BD5 as his handle suggests !
B.E.

You are judged not by what you know, but by what you can do.

RE: Calculating thrust

That engine is larger than a BD5 itself. And if you tried, where would you put the fuel?

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Calculating thrust

BD-5J: last time I looked almost every one of them that had been built to flyable status have since been destroyed in a crash.

RE: Calculating thrust

(OP)
Yes I have BD-5 and I'm working on a ducted fan. So I have the first stage fan j85 not the entire engine is it ways it is bigger than the whole plane.

RE: Calculating thrust

My condolences to your family & friends. They will miss you.

STF

RE: Calculating thrust

BD-5er, I'm not sure if I think that's super cool or insane. Airplanes are way cool, but there's so little margin for error that it's too scary for me. I see the original BD5 jet had something like 265 lbs of thrust. How does that compare to the IC version and what are you aiming for? Have other people done what you're trying? It's fascinating if nothing else.

RE: Calculating thrust

Seems to me that you are going to have great difficulties making it work right or well.

Each part of the J85 is sized and designed to work within the range of operation that the J85 as a whole was intended for. Taking a piece of it isn't necessarily going to give anything close to optimum performance, since it was not intended for ducted fan operation.

TTFN (ta ta for now)
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