Bonjour !
Lightsaber en remet une couche ! Je le suis volontiers !
Logique et techno excellente, ce type d'infos on en re-demande !
Comme quoi, l'équation de RR TXWB, est assez contrôlable et prévisible ... rien en contre, de plus !
Après si Airbus attend 2018 pour le 350-1000, on verra !
Le VAN pour le TXWB, pas encore entendu parler ... une bonne idée à 2% peut être, originellement dans le camp Goodrich !
----------------- Le Post de A.net, N°34 Lightsaber -----------
lightsaber From United States of America, joined Jan 2005, 6580 posts, RR: 96 Reply 34, posted Thu Apr 21 2011 14:44:57 your local timeThu Apr 21 2011 05:44:57 UTC (12 minutes 39 secs ago) and read 34 times: |
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Quoting Baroque (Reply 23): Reading on and between your lines and just plain out guessing what seems likely, is it the case that RR knows on the basis of existing work how to get the beast to 93k, but will have to do quite a bit more work to develop materials that will take it up another 2 or 3 k? In some ways that is a bit surprising as most engines have a few k "in reserve". |
However, engine deveopment must start earlier than airframe. The
initial concept was A350-800 (79k thrust, initially planned to be
derated to 74k for EIS) than the A350-900 (83k thrust). When it became
A350-900, the higher MTOW -800 for ULH, and then the -1000 (with its 93k
of required thrust)... RR was caught flat footed with their 'reserve' already consumed! Think of the Pratt PW4090 being grown from 74k. RR
has done better promising 93k. (Then again, the PW4090 could hit 92k
if it wasn't for high NOx emissions limiting the engine to 90k due to
certification limits.)
The JT9D on the 741 was in the same situation. The thrust required on
the 741 grew beyond Pratt's 'few k in reserve' before EIS. While the
A359 isn't that extreme, it costs fuel burn to leave more than a few
thousand pounds of thrust in reserve; so RR will have to improve materials or do a major configuration change:
Quoting Baroque (Reply 23): The article mentions a bigger fan. How easy would that be to do, and what would that require in the low turbine? |
I would have to know far more of the details of the A350 nacelle than I do.
The GE-90-115
executed a fan diameter increase, so it can be done. It isn't as
optimal as designing the nacelle to that diameter on day 1, but it can
be done. It goes with the 2018 EIS too due to the extensive amont of
rework.
The low compressor would have its diameter increased to feed more air
(for burning more fuel). Compressing more air means the intermediate
turbine would require more horsepower. With a 2 row intermediate
turbine, that should be possible if less cooling air is required for the
high turbine (higher pressure at the inlet of the mid-turbine). With a
larger fan, quite a bit more horsepower will be needed from the low
turbine. The details on how RR
will accomplish that I do not know. It implies the -1000X engine will
require a new casing which is not a cheap option (but allows for major
design changes).
Does anyone know if the A350 has a variable nozzle nacelle? Goodrich
developed the variable nozzle for the PW1000G for the A320neo and they
are developing the A350 nacelle... That is a nice 2% or so drop in fuel
burn with improved climb performance too.
Quoting frigatebird (Reply 33): A dedicated A350RF freighter would blow the 77F off the market however. |
Agreed. It gives Airbus a very competitive offering at least.
Quoting ap305 (Reply 30): Kindly read the air insight interview with Leahy posted earlier in this thread. There appears to be a move towards bumping the mtow upwards along with the thrust. |
More precisely, hot/high performance drops as MTOW goes up. More thrust
helps... but at some point the increased takeoff airspeed (wing limit)
limits the MTOW growth.
I'd love to see a -1000X. The current 'stretch' should be extended to 79.8m.
But that is a 98k engine (if a range hit down to 7,600nm or so could be tolerated).
Lightsaber
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Noter , Quote Astuteman de A.net !
Le TXWB original allait jusqu'à 95 000 lbs !
http://en.wikipedia.org/wiki/Rolls-Royce_Trent
Bien ... rate, de-rate, re-rate ... ils finiront bien par se mettre d'accord sur le rating, sinon c'est la bourse qui va les dérater pour de bon !
JPRS