Latest on Mitsubishi Regional Jet (MRJ)

choi

本文通过一路BBS站telnet客户端发布

James Simms, Japan's New Passenger Jet Takes off Into a Perfect Storm. Wall Street Journal, Sept 24, 2011.
http://online.wsj.com/article/SB10001424053111903703604576588782647706772.html
(Mitsubishi Regional Jet)

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.


--