Jetlagged From United Kingdom, joined Jan 2005, 2462 posts, RR: 17 Reply 1, posted (8 months 2 weeks 3 days 10 hours ago) and read 2771 times:
Rolls Royce turbofan engines use a mixed core and fan exhaust design, hence the longer bypass cowling which is an integral part of the powerplant. Exhaust mixing provides better thrust, reduced fuel consumption and less noise compared to the non-mixed shorter cowled designs as used by PW and GE. The downside is increased weight and drag. RR three shaft engines tend to be shorter than comparable two shaft turbofans so the weight and drag penalty will be less than for a two shaft engine.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 2, posted (8 months 2 weeks 3 days 7 hours ago) and read 2701 times:
Quoting ferpe (Thread starter): Please help me understand why RR designs longer nacelles then GE and PW.
Jetlagged summed it up nicely. A couple of important points to elaborate:
-The nacelle isn't actually longer, it's just that the bypass duct is longer (so it covers up the inner exhaust cone that you can otherwise see on PW and GE nacelles).
-It's not universal...the Trent1000 and GEnX nacelles are very similar (and use the short bypass duct)
-RR is generally unique in usually doing the nacelle/engine as a unified package. The nacelle for PW and GE normally comes from somebody else (and is often designed by the OEM) independently of the engine.
rmm From Australia, joined Feb 2001, 518 posts, RR: 1 Reply 5, posted (8 months 2 weeks 3 days ago) and read 2567 times:
GE thru CFMI used that design on the early A340's. The cfm56-5 on the 340 had a full length duct, similar to the RR design, yet that engine on the A320 didn't. Then to add to the mix, the v2500 on the 320 has a full length duct.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80 Reply 6, posted (8 months 2 weeks 2 days 23 hours ago) and read 2547 times:
Quoting ferpe (Reply 4): Interesting that RR makes their own nacelles and thereby could optimize a little bit differently, I guess they do not make the T1000 nacelle?
I believe the Trent 1000 nacelle comes from Goodrich, same as the GEnX nacelle.
RR used to "own" more of the nacelle package than the other two, in general, including oddities like having the fire extinguisher bottles in the nacelle (the other guys usually have it in the strut or in the fuselage somewhere). In the particular case of the 787, the requirement for the ability to swap engines post-delivery made those kinds of design choices much more difficult and biased them towards a more common approach.
bikerthai From United States of America, joined Apr 2010, 1625 posts, RR: 4 Reply 7, posted (8 months 2 weeks 2 days 11 hours ago) and read 2409 times:
Quoting ferpe (Reply 4): Interesting that RR makes their own nacelles
If my memory serves me right, was the 777 RR nacelle designed and built by Boeing?
If this was the case then two of the reasons are the proprietary method in fabricating the perforated composite inner skins of the inlet and reverser duct, and the pitch graphite honeycomb core of the inner T/R duct wall. I was around when they did R&D for those technology. Saved a lot of weight over existing methods.
Perhaps that is why they kept the nacelles for the 787 also.