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发帖数: 6973 | 1 James Simms, Japan's New Passenger Jet Takes off Into a Perfect Storm. Wall
Street Journal, Sept 24, 2011.
http://online.wsj.com/article/SB10001424
053111903703604576588782647706772.html
Note: Geared Turbofan (GTF) is Pratt and Whitney's invention. Whether it is
as good as touted, it is unclear yet.
(a) geared turbofan
http://en.wikipedia.org/wiki/Geared_turbofan
(The Geared turbofan is a type of turbofan airplane engine, similar to a
turbojet. It consists of a geared ducted fan with a smaller diameter
turbojet engine mounted behind it that powers the fan.)
See the configuration of "turbofan" (whose engine case, the nacelle, is
basically a rim) and "turbojet" in the quotation.
Compare those (configurations) with the one in this web page: There is no
caption but (1) points to the fan and (2), the gear. The gear is placed
between the fan (in front) and the turbine (behind), to decouple (the speeds
of) them (fan and turbine), so that fan can run a third slower than the
turbine.
(b) Bill Saporito, How to Build a Job Engine: Pratt & Whitney labored 20
years to create one new position for one engineer. Hundreds more will
follows. Time, May 30, 2011 (cover date).
http://files.parsintl.com/eprints/22996.pdf
Please read only pp 2-3 (as well as the graphic on p 3):
"Not since the arrival of the Boeing 747 in 1970 had there been serious
innovation in jet engines. They were loud, and they burned a lot of fuel.
The geared turbo engine changed that by putting three innovations together
in a new way. The first is the gearbox. It's lightweight, about 300 lb. (140
kg), and could fit in the trunk of your car, but it generates 30,000
horsepower. All jet-engine design has trade-offs among weight, drag, parts
and power. "Now I have a lighter engine, so I can put a bigger fan on it,"
says Alan Epstein, the company's technology chief. A bigger fan, because it
moves more air, can run slower. That reduces noise. It also means the engine
needs fewer parts to power the turbine. And the engine housing, called the
nacelle, doesn't need as much dampening, so it can be made with lighter-
weight composite materials."
* nacelle (n; French, literally, small boat, from Late Latin navicella,
diminutive of Latin navis ship):
"a streamlined enclosure (as for an engine) on an aircraft"
www.m-w.com
(c) Michael Macham, Baseline Optimism; Pratt says its CSeries and MRJ
engines are meeting predicted fuel efficiency. Aviation Week, Aug 22, 2011.
http://www.purepowerengine.com/pdf/avweek_eprint092211.pdf
Quote from paragraph 3: "Power from Pratt's geared turbofan (GTF) is the
basis for much of the Bombardier's claim. GTF uses a gear to decouple the
engine's ultra-high-bypass fan from the lo-pressure turbine. This allows the
fan to spin a third slower than the turbine, creating less engine noise
while preserving maximum efficiency from the turbine.
(d) Gearig Up for the GTF. Pratt & Whitney's new PurePower PW1000G geared
turbofan has already been chosen for three new narrowbody programmes.
Speculation is growing that the GTF could feature on a re-engined A320 or
737, and even on a future widebody. Chris Kjelgaard looks at this prospects.
Aircraft Technology Engineering & Maintenance, April-May 2010.
http://www.purepowerengine.com/pdf/
GearingUpfortheGTF_ATEM_April-May_2010.pdf
Please start reading from page 89 (unnumbered per se, but to the RIGHT of p
88) with the heading "The PW1000G’s fan and core" --for five paragraphs--
and the companion graphic. |
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