Trent 900 8.7 - 8.5.
|Quoting Keesje (Thread starter):|
- Noise-reducing chevrons on the trailing edge of the bypass duct, (fixed and variable)
- A one piece "jointless" inlet acoustic barrel (Trent900) with negatively scarfed air inlet
- A bigger fan, increasing BPR
- New 3D (composite/hollow titanium) S shaped fan blades and better lpc and hpt blades/vanes (as on newest GE/GP/RR engines).
All of which will do...not a lot!
Bear in mind the cost of redesigning a 5.1 bypass ratio CFM-56-7 to a 7-8 BPR version. The cost of design and certification far outweight any potential benefits. Small tweaks will be the order of the next decade, certainly until an A320/737 replacement appears.
The A320 and 737 aren't particularly noisy anyway. From an airline point of view, it's a lot easier to force pilots to fly more restrictive departure and arrivals routings and place more restrictions on the type of climb thrust selected and the use of reverse thrust than to go through the hassel of getting new and bizarre parts certified.
As for negatively scarfed inlets, RR
have been doing research (as well as Airbus proper) on the design. The idea might be useful for the A320 and IAE (RR) equiped varients do suffer from distinctive (and annoying) buzz-saw noises from the LP
fan. However, the negatively scarfed intakes disrupt the intake air, and even though the A320 and 737 operate at the begining of the transonic regime, shocks from the negatively scarfed intakes (apparently) have reduced engine efficiency in tests. Modified inlets and particularly increases BPR certainly come with weight and drag penalties. Increased BPR increases NOX emissions also. The choice in this area is between noise and emissions.
The better solution would be continue to tweak current designs (modified burners, active and passive acoustic linings, stricter adherance to FMC VNAV paths, new approaches, increasing overall pressure ratios graduly, using active stators, using the FMS to manage thrust levels and hence noise impact, a la A380). When new aircraft come along, then drastic changes can be made.
Certainly the big challenge for aircraft manufacturers right now is to figure out what the situation is regarding the use of oil. It's no good Boeing and Airbus developing A320/737 replacements now, when in a decade it becomes clear that XYZ technology is well on the way to banishing the use of crude oil.