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Single Spool GTF  
User currently offlineMrocktor From United States of America, joined Jan 2005, 1671 posts, RR: 49
Posted (5 years 8 months 2 weeks 3 days 6 hours ago) and read 3929 times:

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?

8 replies: All unread, jump to last
 
User currently offlineCFMTurboFan From Canada, joined May 2007, 41 posts, RR: 0
Reply 1, posted (5 years 8 months 2 weeks 3 days 4 hours ago) and read 3904 times:

I don't think so, but I will let the design engineers answer that in more detail.

User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 2, posted (5 years 8 months 2 weeks 2 days 18 hours ago) and read 3800 times:



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.


User currently offlineCobra27 From Slovenia, joined May 2001, 1030 posts, RR: 0
Reply 3, posted (5 years 8 months 2 weeks 2 days 9 hours ago) and read 3737 times:

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


User currently offlineMrocktor From United States of America, joined Jan 2005, 1671 posts, RR: 49
Reply 4, posted (5 years 8 months 2 weeks 2 days 6 hours ago) and read 3712 times:



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


User currently offlineLightsaber From United States of America, joined Jan 2005, 13440 posts, RR: 100
Reply 5, posted (5 years 8 months 1 week 6 days 21 hours ago) and read 3557 times:
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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



Societies that achieve a critical mass of ideas achieve self sustaining growth; others stagnate.
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 6, posted (5 years 8 months 1 week 6 days 19 hours ago) and read 3527 times:



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 :-)
User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6515 posts, RR: 54
Reply 7, posted (5 years 8 months 1 week 6 days 18 hours ago) and read 3514 times:



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, Preben Norholm
User currently offlineMrocktor From United States of America, joined Jan 2005, 1671 posts, RR: 49
Reply 8, posted (5 years 8 months 1 week 6 days ago) and read 3426 times:

Very good points guys, thanks for the feedback.

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