mrocktor
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Single Spool GTF

Mon Mar 16, 2009 12:48 pm

Someone mentioned in another thread that the LPT on the PW GTF will run at speeds similar to the core. If this is true, would a single shaft design be viable? If so, how significant would the weight and maintenance gains be for such a design?
 
CFMTurboFan
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RE: Single Spool GTF

Mon Mar 16, 2009 2:58 pm

I don't think so, but I will let the design engineers answer that in more detail.
 
tdscanuck
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RE: Single Spool GTF

Tue Mar 17, 2009 1:20 am



Quoting Mrocktor (Thread starter):
Someone mentioned in another thread that the LPT on the PW GTF will run at speeds similar to the core. If this is true, would a single shaft design be viable?

It might work for one particular operating point, but probably not across the range of thrusts that a commerial engine needs to. The LP spool speed tends to vary a lot more with throttle than the HP spool. If you went to single spool you'd probably need more stablizing stuff (variable stators, surge valves, etc.) to keep the engine happy during transients.

Tom.
 
cobra27
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RE: Single Spool GTF

Tue Mar 17, 2009 10:33 am

Interesting question!

I had a diploma a month ago comparing turbofans with their aeroderivatives. And actually I didn't know how many shafts there will be on GTf. Proffesor suggested that there will beonly one shaft, but PW 1000G will have 2. And planetary reductor is placed in the front of the engine
 
mrocktor
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RE: Single Spool GTF

Tue Mar 17, 2009 1:31 pm



Quoting Tdscanuck (Reply 2):
It might work for one particular operating point, but probably not across the range of thrusts that a commerial engine needs to.

This makes a lot of sense to me, thanks! I guess the single spool turbofan will have to wait for a CVT transmission  Big grin
 
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lightsaber
Crew
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RE: Single Spool GTF

Thu Mar 19, 2009 10:37 pm



Quoting Mrocktor (Thread starter):
Someone mentioned in another thread that the LPT on the PW GTF will run at speeds similar to the core.

Nyet.

I do *not* know the exact RPM of the PW1000G, but I've worked on larger GTF's.

Fan, at 74" will probably be at ~1900 RPM.
Low spool (other side of gearbox) I estimate at 3X the fan or ~5600RPM.
The high spool will be in the 12,000 to 15,000 RPM range.

The PW 1000G would not be competitive from a fuel efficiency standpoint as a single spool. Both versions are twin spool designs with more in common with a PW6000 and other 'large' Pratt engines than any other PWC powerplant. however... there are details that are unique PWC.  Wink

Quoting Mrocktor (Reply 4):
I guess the single spool turbofan will have to wait for a CVT transmission

 rotfl  Not at GTF horsepower ratings.

Lightsaber
"They did not know it was impossible, so they did it!" - Mark Twain
 
KELPkid
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RE: Single Spool GTF

Fri Mar 20, 2009 12:26 am



Quoting Lightsaber (Reply 5):
Not at GTF horsepower ratings.

And what would those be?  eyebrow 

I suppose it's a moot point unless someone is planning a GTF-derived turboprop, GTF-powered ship or stationary power generator, or a GTF-powered dragster  Wink

Hmmm, wonder how I could side track this discussion futher  scratchchin  GTF-derived turbine-electric locomotive, anyone? The GTF powerplant would have to turn an electric alternator, which would in turn power a set of traction motors down in the axles. I suppose if you roof-mounted the engine, the thrust of the fan portion might actually make a meaningful contribution to the forward motion of the train...  cool 
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
prebennorholm
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RE: Single Spool GTF

Fri Mar 20, 2009 1:01 am



Quoting Lightsaber (Reply 5):
I do *not* know the exact RPM of the PW1000G, but I've worked on larger GTF's.

Fan, at 74" will probably be at ~1900 RPM.
Low spool (other side of gearbox) I estimate at 3X the fan or ~5600RPM.
The high spool will be in the 12,000 to 15,000 RPM range.

Yes, but those ratioes would be only when the engine produces power.

Talking about ground idle I would assume a totally different HP/LP RPM ratio. Maybe something like 6-7,000 RPM on HP, less than a thousand RPM on the LP tubine and only a few hundred on the fan.

Then talk about starting the engine. On a similarly sized single spool GTF the starter would have to spool also the fan up to many hundred RPM. That wouldn't be practical.

A single spool GTF would be as impractical as a single spool turboprop.

On for instance the PW127 on the ATR the HP/LP RPM ratio goes all way to infinite. It has a brake which puts the LP spool at a complete stand still while the HP spool runs at idle and functions as an APU.

A single spool GTF might work just fine at full power. But starting it would be unnecessarily difficult and power consuming. And true idle would be almost nonexistant. But throttle responce with the fan acting as a flywheel on the HP spool - I don't even dare to estimate the operational complications and limitations.
Always keep your number of landings equal to your number of take-offs
 
mrocktor
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RE: Single Spool GTF

Fri Mar 20, 2009 7:25 pm

Very good points guys, thanks for the feedback.

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