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PW1500G Analysis, The GTF For C-series  
User currently offlineferpe From France, joined Nov 2010, 2804 posts, RR: 59
Posted (1 year 7 months 1 week 2 days 5 hours ago) and read 9850 times:

As can be seen in the TF42 thread I am learning to analyse the typical civil turbofans we encounter. Right now I am into GTFs and I therefore did an anlysis of the C-series engine, the PW1500G, to train for my improvement of the TF42 GTF. Having done all the fiddling to get a model fit in GasTurb12 I thought I might as well post it here, so here goes:

Engine cut-through from PWs datasheet:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/PW1500Gcutthrough_zpsbe8f93f0.jpg

TCDS from certification https://www.box.com/s/76cq9bwbf22ikh1trjum

To understand an engine one must understand it's application, the reason is the base engine is designed with the most stressing aerodynamic design point in mind, Top of Climb (ToC). ToC is where the engine must get the frame to it's initial cruise height ( where the wings work in their design range of normally Cl around 0.5 carrying some 95% of MTOW ) with at least 300ft/min climb left. Here now a table from my frame model with the C-series engine requirements, I also included the most direct competitors for reference (click on all tables to see better) :

http://i298.photobucket.com/albums/mm262/ferpe_bucket/C-serieswithcompetitorsenginedata_zps4127ebaa.jpg

The cursor is on the heaviest C-series, the 130ER which is therefore setting the design point thrust. We need 2* 4200lbf just before we reach FL350 to still have some climb in the kite after take-off. This climb is done at the max continuous thrust (or lower in the real case where cost-index flying is done) normally limited by Turbine Inlet or Stator vane Outlet Temp (TIT/SOT), also called T41 in engine speak  , see principle picture from GasTurb about the standardized measurements points in a Turbofan (called stations) :

http://i298.photobucket.com/albums/mm262/ferpe_bucket/T39stations_zps58249340.jpg


PW/MTU has given very little data about the 1500G and they would certainly not publicize TIT/SOT  Wow! , this is guarded stuff. But the TCDS gives an EGT and it was within 30° C of my T45 temp (between HPT and LPT) so I let this be the limiters of the max continuous (limit for ToC, Climb etc) and take off thrusts (TO, which has a higher temp allowed for 5 minutes). Here the table with my data for the PW1500G:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/PW1500Ganalysis_zps3db93b4f.jpg

The columns are:

- Top of Climb for the PW1524G, followed by initial cruise at FL350, then average cruise at FL 370 and final cruise at FL 410, then take off thrust and climb thrust at V2 ie direct after take-off, then the typical climb thrust at FL100 and 200

- Then the take off thrusts for the two derated variants of the 1500G as described in the TCDS. These are just spinning slower and therefore have lower pressure ratios and higher BPR (as the core is passing proportionally less mass flow at the lower ratings, it does not have to work so hard to generate the demanded engine thrust).

As can be seen the PW1500G has thrust to spare on the design point but it gets closer on the one engine out thrust requirements of 17.5 klbf (engine delivers 19.4klbf). An interesting comparison is in the tables row 97 where I have a standard assumed lapse rate of 18% at M 0.2 which is the typical V2 speed. The 1500G is a very high BPR engine at around 12, it therefore loosed more thrust with speed, which also can be seen from the data. TSFC of around 0.54 is as expected, this is the bare engine. It looses about 2% in internal nacelle losses so would have an installed TSFC around 0.55. Net contribution to the frames fuel burn would also have to take into account the higher drag and weight from the large nacelle of a high BPR engine.

So how close to reality is this analysis? Well I don't think it is to far off. As OldAeroguy would say "it is certainly better then handwaving"  .

[Edited 2013-02-23 05:30:20]


Non French in France
14 replies: All unread, jump to last
 
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5472 posts, RR: 30
Reply 1, posted (1 year 7 months 1 week 1 day 9 hours ago) and read 9425 times:

Quoting ferpe (Thread starter):
So how close to reality is this analysis? Well I don't think it is to far off. As OldAeroguy would say "it is certainly better then handwaving"

That the GTF is already certified, and Pratt isn't foreshadowing any performance shortfalls, is telling, in my opinion. They are very, very confident about the engine...you can almost hear the giggling. The Leap is going to be an amazing engine, combining the absolutely bleedingest edge materials and production techniques to squeeze every last drop of fuel efficiency out of their engine...and Pratt got about 90% of those gains will little more than a single ratio, planetary gearbox.

The die is cast. Pratt hit on 17 and was dealt a blackjack. What we're seeing is the 21st century JT8...the engine that will be the gold standard, possibly for decades to come.

Within a decade, (probably less), GE will announce a revolutionary new concept in jet engines which will have a clever acronym describing a way to have the fan and low pressure spool directly connected but able so spin at different speeds so different discs spin at their optimum speeds, drastically increasing efficiency without needed more expensive, exotic materials. This might be accomplished using gears but it will both be radically different than the GTF while being almost exactly the same.



What the...?
User currently offlinefaro From Egypt, joined Aug 2007, 1551 posts, RR: 0
Reply 2, posted (1 year 7 months 1 week 1 day 7 hours ago) and read 9403 times:

Quoting JoeCanuck (Reply 1):
The Leap is going to be an amazing engine, combining the absolutely bleedingest edge materials and production techniques to squeeze every last drop of fuel efficiency out of their engine...and Pratt got about 90% of those gains will little more than a single ratio, planetary gearbox.

And PW will be able to implement all those materials advances and production techniques at their leisure over the next 10 years. Definitely easier to do than design a geared turbofan from scratch. All power to them, great to see PW back again in the main league of engine makers!!

Quoting JoeCanuck (Reply 1):
Within a decade, (probably less), GE will announce a revolutionary new concept in jet engines which will have a clever acronym describing a way to have the fan and low pressure spool directly connected but able so spin at different speeds so different discs spin at their optimum speeds, drastically increasing efficiency without needed more expensive, exotic materials. This might be accomplished using gears but it will both be radically different than the GTF while being almost exactly the same.

Yes. What troubles one is the speed with which GE may be able to finalise this design, especially with their purchase of Avio, the GTF's Italian fan gearbox manufacturer:

http://www.aviationweek.com/awmobile...l/AW_12_24_2012_p44-530390.xml&p=2

I wonder whether this purchase gives them unfettered access to the GTF gearbox technology or whether this is covered by PW intellectual property rights...

In the meantime though, the market will be in PW's hands.


Faro



The chalice not my son
User currently offlineferpe From France, joined Nov 2010, 2804 posts, RR: 59
Reply 3, posted (1 year 7 months 1 week 1 day 5 hours ago) and read 9362 times:

I think PW has a winner on their hands. One shall not forget MTU however, they have major piece of the engine (high compressor, low turbine), there are also other partners AVIO and VOLVO Aero (now GKN). Here is a very nice writeup spelling out who did what and what some of the benefits and challenges where (done during the run up to todays certified engine some 5 years ago:

http://mtu-epool.com/en/technologies...ler_Geared_turbofan_technology.pdf

It is a bit unusual that a partner does the HPC, this is high tech and normally a thing for the main vendor, but MTU saved PW on the PW6000 by taking over the HPC and did a good job, they then continued that on the GTF. Avio now being a GE company is a problem, let's see how this is handled.

Here a nice picture of the PW1500G applications on the different C-series models with the base engine being circled:

http://i298.photobucket.com/albums/mm262/ferpe_bucket/PW1500GandC-seriesrange_zps5864ab9c.jpg



Non French in France
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5472 posts, RR: 30
Reply 4, posted (1 year 7 months 1 week 14 hours ago) and read 9144 times:

Quoting faro (Reply 2):

Yes. What troubles one is the speed with which GE may be able to finalise this design, especially with their purchase of Avio, the GTF's Italian fan gearbox manufacturer:

It doesn't trouble me...it is inevitable. Multi spool, high bypass, etc were all genies that once let out of the bottle, spread like wildfire. No advantage lasts forever. Pratt went with the GTF and currently enjoys the lead. What they can't do is sit on their laurels. GE has proven to be a tenacious competitor to the GTF and that's without their own geared fan.

Having these guys push each other will mean amazing things moving forward.

In the meantime, Pratt deserves every penny and accolade they receive and they will get plenty of both when the CSeries takes to the air.



What the...?
User currently offlineAA737-823 From United States of America, joined Mar 2000, 5844 posts, RR: 11
Reply 5, posted (1 year 7 months 5 days 8 hours ago) and read 8760 times:

Quoting ferpe (Thread starter):
To understand an engine one must understand it's application,

Yes, yes. But... I LOVE jet engines, but it's nearly 1am, and I cannot tread through all of your information. I'll have to try it after a good night's sleep!

Quoting JoeCanuck (Reply 1):
The die is cast. Pratt hit on 17 and was dealt a blackjack. What we're seeing is the 21st century JT8...the engine that will be the gold standard, possibly for decades to come.

Clearly, you're just as optimistic as they are! I think you might be right, but I'm a bit more guarded.
For example, okay, they've got the C-series exclusivity. What about the 737? Boeing is sticking with LeapX exclusively. 100 C-Series planes does not 1000 737Max planes make!

Quoting faro (Reply 2):
And PW will be able to implement all those materials advances and production techniques at their leisure over the next 10 years. Definitely easier to do than design a geared turbofan from scratch. All power to them, great to see PW back again in the main league of engine makers!!

Tell me this: if I'm not mistaken, the GTF was a clean sheet design, right? Or was it simply a gearbox slapped into a PW6000? I thought it was all new...


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5472 posts, RR: 30
Reply 6, posted (1 year 7 months 4 days 16 hours ago) and read 8618 times:

Quoting AA737-823 (Reply 5):
For example, okay, they've got the C-series exclusivity. What about the 737? Boeing is sticking with LeapX exclusively. 100 C-Series planes does not 1000 737Max planes make!

That means Pratt sold hundreds of engines they wouldn't have otherwise. The GTF is on not only the CSeries but A320, E-jet, MRJ and whomever else might go for it.

They went from being completely out of the narrow body market to one of the major players. Rolls likes the idea so much they decided to team up with Pratt.



What the...?
User currently offlineferpe From France, joined Nov 2010, 2804 posts, RR: 59
Reply 7, posted (1 year 7 months 4 days 11 hours ago) and read 8564 times:

Quoting AA737-823 (Reply 5):
What about the 737? Boeing is sticking with LeapX exclusively

The DDTF (direct drive turbofan) is an effective architecture if you have limited fan space like the 737. As you see in the TF42 last post the GTF only starts to shine if the bypass ratio goes higher then what is practical with a DDTF. What is important in a 737 situation is to work with someone that can make the most out of the 69'' fan available, that is GE. They can make the most performant (=hot) core, this means a smaller core can drive the fan which gives you the highest BPR possible in the available space. A high performance core and the highest BPR possible gives the 737MAX the lowest fuel burn they can hope for. Together with the lighter frame and somewhat better wing it makes the MAX about even with the neo (at least what we know now).

Quoting AA737-823 (Reply 5):
Tell me this: if I'm not mistaken, the GTF was a clean sheet design, right? Or was it simply a gearbox slapped into a PW6000?

The PW1500 is clean sheet, the PurePower demo engine which was flown on the A340 was built on the PW6000 core. The PW6000 was built to be simple and cheap to maintain, this was before the oil cost 100$ per barrel, that core was not good enough to build a LEAP beater. PW and MTU therefore started new for the real GTF generation.



Non French in France
User currently offlineAA737-823 From United States of America, joined Mar 2000, 5844 posts, RR: 11
Reply 8, posted (1 year 7 months 2 days 5 hours ago) and read 8280 times:

Quoting ferpe (Reply 7):
The DDTF (direct drive turbofan) is an effective architecture if you have limited fan space like the 737. As you see in the TF42 last post the GTF only starts to shine if the bypass ratio goes higher then what is practical with a DDTF. What is important in a 737 situation is to work with someone that can make the most out of the 69'' fan available, that is GE. They can make the most performant (=hot) core, this means a smaller core can drive the fan which gives you the highest BPR possible in the available space. A high performance core and the highest BPR possible gives the 737MAX the lowest fuel burn they can hope for. Together with the lighter frame and somewhat better wing it makes the MAX about even with the neo (at least what we know now).

Okay, so, all of that said, do you think that there isn't any point to Pratt competing for the 737MAX? Because it's not optimized for that application?


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5472 posts, RR: 30
Reply 9, posted (1 year 7 months 2 days 2 hours ago) and read 8260 times:

Quoting AA737-823 (Reply 8):

Okay, so, all of that said, do you think that there isn't any point to Pratt competing for the 737MAX? Because it's not optimized for that application?

I think that goat has left the barn. The only way I could see Pratt being called on to make an engine for the MAX, is if the Leap is a complete dog...which I don't think it will be.

Once they decided on a fan size smaller than what the GTF can currently do, they took away some of the advantages of the GTF, which is a somewhat slower spinning fan. Once they decided on a smaller fan, they get to spin it more quickly.

My gut tells me that the advantages of a geared fan are greater, the larger the fan. Pratt has said they won't be offering an engine for the 777x...but I wonder if a new company combining RR and Pratt might.



What the...?
User currently offlinedouglasyxz From Germany, joined Jan 2013, 99 posts, RR: 0
Reply 10, posted (1 year 6 months 4 weeks 22 hours ago) and read 8031 times:

Since GTF engine seem to be more complex due to the gearbox, I would assume maintenance costs would be higher than those of "conventional" engines. More parts involved, more friction...

1. Is that true?
2. Could this be a decision making point for airlines buying a NEO to go for the Leap instead? If the answer to question 1 were yes, what incentive could PW offer to get the deal finally?

I know the history of PDK gearbox of Audi quattro groupe B rally car; it took quite a long time until this new kind of gearshift had arrived as DSG in VWs mass production. A little off topic the link to cars but I'm wondering how PW resp. MTU can achieve the requested reliability right from the beginning, considering the GTF is a clear-sheet design.


User currently offlineEaglePower83 From United States of America, joined Oct 2011, 245 posts, RR: 0
Reply 11, posted (1 year 6 months 4 weeks 2 hours ago) and read 7880 times:

Quoting douglasyxz (Reply 10):

Since GTF engine seem to be more complex due to the gearbox, I would assume maintenance costs would be higher than those of "conventional" engines. More parts involved, more friction...

1. Is that true?
2. Could this be a decision making point for airlines buying a NEO to go for the Leap instead? If the answer to question 1 were yes, what incentive could PW offer to get the deal finally?

I know the history of PDK gearbox of Audi quattro groupe B rally car; it took quite a long time until this new kind of gearshift had arrived as DSG in VWs mass production. A little off topic the link to cars but I'm wondering how PW resp. MTU can achieve the requested reliability right from the beginning, considering the GTF is a clear-sheet design.
http://www.sae.org/aeromag/techinnovations/1298t10.htm

1. This is false. The gearbox does add some components and complexity, however it reduces airfoils and compressor stages, thus a net savings in components and maintenance costs. The gearbox has been developed for over 10 years, is over 99% efficient (which is amazing!) and I'd be willing to bet PW knows exactly what the life expectancy is out of the gear components to set a highly conservative and predictable maintenance schedule.
Theoretically speaking, it's faster and cheaper to pull out a gearbox unit than to dissassemble and replace airfoils.
Running the engine cooler than GE's offering allows those few airfoils left, to stay in service longer, further reducing operating costs.

2. This is NEW technology, and from what I understand, aerospace customers are quite risk-averse. That said, there's a lot of promise and trust in the GTF system, since Airbus, BA, MRJ and now EMB have chosen the engine. They've held the gears in their hands. Wtih near $1B in development and thousands of hours of on and off-wing testing. This gearbox will be robust as hell.


User currently offlinejambrain From United Kingdom, joined Sep 2008, 251 posts, RR: 0
Reply 12, posted (1 year 6 months 3 weeks 6 days 22 hours ago) and read 7838 times:

Quoting EaglePower83 (Reply 11):

thousands of hours of on and off-wing testing. This gearbox will be robust as hell.

I hope you've got your   , no matter how hard I test, production service always throws something new! You can't possibly imagine every variable that real service throws at you.



Jambrain
User currently offlinedouglasyxz From Germany, joined Jan 2013, 99 posts, RR: 0
Reply 13, posted (1 year 6 months 3 weeks 6 days 21 hours ago) and read 7816 times:

Quoting EaglePower83 (Reply 11):

That's interesting, thanks for the link. I was checking PW's website too and I must admit I wasn't aware GTF saves so many parts, runs cooler and less noisy. Can't wait to see it on LX's CSeries next year.   

Is there a weight difference compared to conventional engines? More weight due to gearbox or less due to fewer airfoils?

Anyway, all the luck to PW and BBD and I wish they can grab a lot more orders and have a healthy future with this aircraft.


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5472 posts, RR: 30
Reply 14, posted (1 year 6 months 3 weeks 6 days 16 hours ago) and read 7756 times:

Quoting jambrain (Reply 12):
I hope you've got your , no matter how hard I test, production service always throws something new! You can't possibly imagine every variable that real service throws at you.

Look at the Boeing batteries...they tested the hell out of them and a monkey wrench still got tossed into the mix.

Anything 'made' can fail. That being said, I have faith that Pratt has beaten the hell out of these things every way they can think of and are still doing it 24/7.



What the...?
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