Superstring From Austria, joined Jun 2007, 46 posts, RR: 0 Posted (4 years 6 months 2 weeks ago) and read 10351 times:
Well I have a question about the RR Trent 1000 and the GE GENX for the Boeing 787. Internal papers Airbus has gathered about the 787 (which where recently revealed by flightblogger http://www.flightglobal.com/blogs/fl...ger/Airbus_787_Lessons_learnt.pdf) states that both engines miss their specified fuel burn rates by several percent (see page 16 in the that report)
Well I just want to know if anyone out there has more accurate data, as it appears to me that the statement: "Rumoured to have missed SFC target by..." is not really a valid and reliable source for such a conclusion.
Baroque From Australia, joined Apr 2006, 15380 posts, RR: 59 Reply 1, posted (4 years 6 months 1 week 6 days 6 hours ago) and read 10234 times:
Hmmm. I guess over 17 hours of deathly silence is the answer to your most interesting question Superstring. Those who know - and there are some on a.net - cannot say, and the rest of us are dying to know but do not know anything useful. The known addition of another stage to the TXWB or T17whatever might be a bit of a hint. But how the T1000 is fixed (or not) remains a mystery for the most part.
The bit about a revised LPT with "broader chord blades" is interesting. ?Not usual RR terminology, they usually speak of wide chord and presumably would write "wider". With a new casing, it would be effectively a differently dimensioned engine.
Where is Lightsaber (I wrote where is La, but I feared someone would tell me "near the San Andreas fault - or worse)??
Keesje From , joined Dec 1969, posts, RR: Reply 3, posted (4 years 6 months 1 week 1 day 13 hours ago) and read 9888 times:
I think the delays of the 787 /747-8 should have given or will RR/GE time to fix things if they were easy to fix. Maybe they are not easy to fix. Redefining blades in the LPT is indeed a significant modification. It would be a new version in regular product development.
SunriseValley From Canada, joined Jul 2004, 4002 posts, RR: 4 Reply 4, posted (4 years 6 months 1 week 1 day 12 hours ago) and read 9872 times:
In another thread it is reported that Boeing are anticipating a lower fuel burn than originally expected on the 747-8i . Seems rather contradictory to me unless the initial SFC numbers for the two different GEnx versions were out of whack somewhere.
Astuteman From United Kingdom, joined Jan 2005, 9264 posts, RR: 96 Reply 5, posted (4 years 6 months 1 week 23 hours ago) and read 9768 times:
Quoting SunriseValley (Reply 4): In another thread it is reported that Boeing are anticipating a lower fuel burn than originally expected on the 747-8i . Seems rather contradictory to me unless the initial SFC numbers for the two different GEnx versions were out of whack somewhere.
(I've just posted this on another thread - apologies for the copy/paste)...
GE are on record (a while back) as saying the GEnx is 4% more efficient than the GP7000 on that's on the A380. The EA are busy improving THAT engine by 2%
If the GEnx indeed misses its fuel burn by 2%-3%, then its SFC is going to be only 1%-2% better than the GP7000 TODAY, and worse than it will be in 2012.
You can construct a similar argument for the Trent 1000 vs Trent 900 comparison.
I don't personally believe that large (as in >1%) misses in SFC will be ultimately be realised on the 787's engines.
Baroque From Australia, joined Apr 2006, 15380 posts, RR: 59 Reply 6, posted (4 years 6 months 1 week 22 hours ago) and read 9755 times:
Quoting Astuteman (Reply 5): You can construct a similar argument for the Trent 1000 vs Trent 900 comparison.
True except it was being assumed that most of the T900 improvements would be worked in from T1000 features. So while there is a + to the POSSIBLE problems, there is also a negative. If the T1000 does not work as advertised, there might be fewer improvements to work back into the T900.
Quoting Astuteman (Reply 5): I don't personally believe that large (as in >1%) misses in SFC will be ultimately be realised on the 787's engines.
Hope you are right. Is that what the back of your fag packet says?
Parapente From United Kingdom, joined Mar 2006, 1320 posts, RR: 10 Reply 7, posted (4 years 6 months 6 days 17 hours ago) and read 9562 times:
What it all does suggest is that both manufacturers are working to the absolute limit of their knowledge to wring out the best fuel consumption (for a given power) possible. Thats a good thing for everyone and the environment as well.
It is (I believe) broadly accepted that gearing a huge engine (and these are big B*****s) would put an intolerable (dangerous) stress on any gearbox. As such these 2 engines are about as good as it gets.
Of course the pressures will be slowly ramped up,silicon Blisks will also help and cleaner buning at the backend.But its going (I believe) to be very incremental from now on.
And yes I still believe that the XWB core is fundamentally that of the 900 so any developments on the former will find themselves on the latter (rather than a complete reengine of the 380 -off topic I know)
Baroque From Australia, joined Apr 2006, 15380 posts, RR: 59 Reply 8, posted (4 years 6 months 6 days 2 hours ago) and read 9416 times:
Quoting Parapente (Reply 7): And yes I still believe that the XWB core is fundamentally that of the 900 so any developments on the former will find themselves on the latter (rather than a complete reengine of the 380 -off topic I know)
Not really off topic as that sets the way in which RR will progress, rather than the "clean" swap that seems so attractive to most of the rest of us.
Jambrain From United Kingdom, joined Sep 2008, 235 posts, RR: 0 Reply 9, posted (4 years 6 months 5 days 10 hours ago) and read 9291 times:
Quoting Parapente (Reply 7): And yes I still believe that the XWB core is fundamentally that of the 900 so any developments on the former will find themselves on the latter (rather than a complete reengine of the 380 -off topic I know)
module weight savings of 15 per cent and aerodynamic efficiency improvements via the use of compressor blisk technology... second stage of IP turbine for improved efficiency and greater capability...new bearing system, using larger bearings with increased load capability bringing fuel burn benefits
Baroque From Australia, joined Apr 2006, 15380 posts, RR: 59 Reply 10, posted (4 years 6 months 5 days 6 hours ago) and read 9251 times:
Quoting Jambrain (Reply 9): Quoting Parapente (Reply 7):
And yes I still believe that the XWB core is fundamentally that of the 900 so any developments on the former will find themselves on the latter (rather than a complete reengine of the 380 -off topic I know)
module weight savings of 15 per cent and aerodynamic efficiency improvements via the use of compressor blisk technology... second stage of IP turbine for improved efficiency and greater capability...new bearing system, using larger bearings with increased load capability bringing fuel burn benefits
"fundamentally" the same ? eyebrow
Fairly obviously a heck of a lot of new engineering is going into this latest and presumably greatest version.
They are holding to the name Trent (although a new name does seem to have been discussed), presumably partly because of the reputation of Trents (hard won) and presumably partly because the basic layout is still the same.
Mind you module weight savings of 15% might get a bit diluted with the extra weight coming from the extra IPT stage.
At one extreme, they could rename for the smallest of change and at the other hold the same name while making major alterations.
Presumably, the great advantage of the TXWB is that it will have built into the design the lessons from the T1000. Equally some of the TXWB "fixes" will assist the T1000 so it is not left an orphan.
But Parapente still has a point that with the design of these engines, it is presumably relatively easy to
engineer later improvement back into earlier designs. So perhaps the discordance is more apparent than real??? Just depends on the point of view.
Apart from the "blisks", aerodynamic enhancements, 2nd stage IP, and new bearings, I also understand the Trent-XWB to have (slightly) higher BPR and PR than the T900 or T1000, but also to be fundamentally much more aggressive in terms of materials and core temperatures than either of the previous engines...
Quoting Baroque (Reply 10): it is presumably relatively easy to
engineer later improvement back into earlier designs
Some will, but some won't.
I suspect some materials improvements could be retrofit, and possibly some of the aerodynamic changes, but fundamentals like PR and BPR, and extra stages, are pretty much unique to the engine architecture, as far as I can understand.
That said, I'm not an expert - just a very interested amateur..
Parapente From United Kingdom, joined Mar 2006, 1320 posts, RR: 10 Reply 12, posted (4 years 6 months 5 days ago) and read 9169 times:
Of course it is only supposition.
But creating brand new engines from scratch is very very expensive.I believe you can see when and where they really throw the big bucks. On the 340-500/600 series for example the whole project was conducted on a "quick and cheap" basis to get the product out befoe Boeing (77W) and hope that oil stayed cheap.The plane is fundamentally 2 additional wing plugs and two additional fuselage plugs.The engine took an existing core and was refanned.It looks (to me) that it was all about price. Rolls did already have (in a demonstrator) the contra rotating core but chose not to develop it for what I believe they saw as a limited run.
On the other hand for the T900 they pulled out all the stops.The same is also true of the T1000. Now core size abosoluty governs final power. The T900 was from the outset able to deliver 80,000 lbs of thrust and far more on bench testing. The XWB requires this level (bench) of thrust.You then have all the technilogical improvements designed into the T1000 and a few more (blisk's) besides. Why design a new core from scratch when you already have one? It would not be a sound business move would it. Furthermore in the same way the 767 was a good partner to the 747-400 with very similar engines so too would the XWB be to the 380.Making it more attractive to buyers.
I totally accept that they have recently had to add an extra stage -but this was not in the origonal plan.
Very interesting. It could be argued that the T500 performance (or lack of it in terms of cruise SFC) came back to bite RR a bit, at least on these threads.
Quoting Astuteman (Reply 11): Apart from the "blisks", aerodynamic enhancements, 2nd stage IP, and new bearings, I also understand the Trent-XWB to have (slightly) higher BPR and PR than the T900 or T1000, but also to be fundamentally much more aggressive in terms of materials and core temperatures than either of the previous engines...
An aggressive Roller - ouch! How ungentlemanly would that be?
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