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[messymarsh]

if i were to connect a central axis to the turbine in a small jet engine and down gear it using planetary gearing is there potential for jet a type engine to put out some "real" tourque is there a way i could figure this in foot lbs using the thrust? absolute pressure? thermal efficiency?

 

[Cyrus]

It's called a turboshaft engine. Airplanes use it to drive propellers all the time.

All you need to know is the engines shaft power and rpm. You can then calculate the torque easy enough.

 

[messymarsh]

alright thank you the reason i was wondering this was for an engine design I am working on and was planning on converting a couple small jet engines to the turboprob design which i had sort of redesigned to fit what I am working on. while looking online for turboprop engines everything iv found is to small or much to large for what i need. if i were to convert a normal jetengine to the turbotrop type would the airflow of the engine on the exhaust be interupted to greatly and require making extensive changes to the cumbuster and compressor?

 

[jack action]

If you want to know the power output of a jet engine, you have to multiply the thrust by the exhaust gas velocity (assuming the engine is stationary). Since jet engine are rarely used in a fixed position, it might be easier to find the top speed of an airplane that has the engine and multiply it by the thrust of one engine to find its power. See http://en.wikipedia.org/wiki/Thrust#Thrust_to_power".

If you want to modify a jet engine to turboprop, you have a heck of a challenge. If you refer to Cyrus' drawing, you'll notice that there are 2 turbines. The first one is used to power the compressors (On some models there might be more than one). The second one is used to power the output shaft. The basic difference between a jet engine and a turboprop is that the jet engine doesn't have the second turbine, hence all the energy goes to moving the exhaust gases instead of turning the second turbine. So to transform a jet engine into a turboprop, you need to add this turbine.

Of course, there will be more losses with that turbine than exhaust gas exiting a duct, so you won't recuperate all the power that was calculated earlier but it will give you a ballpark figure.

 

[zfolwick]

I thought that there was usually 1 turbine for the medium compressor, 1 turbine for the high compressor, and another for the fan (this is in a turbofan). In a turbojet, there would only be 2 right?

 

[dtango]

if i were to connect a central axis to the turbine in a small jet engine and down gear it using planetary gearing is there potential for jet a type engine to put out some "real" tourque...

You bet you :).

[PLAIN]http://thetongsweb.net/images/agt1500a.jpg

This gas turbine engine has enough torque to power this 68 ton badboy at 41 mph

[PLAIN]http://thetongsweb.net/images/m1a2.gif

Here's the rated torque of the AGT-1500 gas turbine engine...

[PLAIN]http://thetongsweb.net/images/agt1500b.jpg

For grins, here's a schematic of the main parts of the AGT-1500...

[PLAIN]http://thetongsweb.net/images/m1-abrams-tank-power-pack.jpg

Cheers!