General Electric GEnx

The General Electric GEnx (General Electric Next-generation) is an advanced turbofan under development by GE-Aviation for the Boeing 787 & 747-8. After the initial unveiling GE Aviation decided to offer the engine for the original Airbus A350 as well but not its current version, the A350 XWB. The GEnx is intended to replace the CF6 in GE's product line. The current model GEnx-2B was first tested on 29 February, 2008.

History and description

The GEnx and the Rolls-Royce Trent 1000 were selected by Boeing following a run-off between the three big engine manufacturers. Pratt & Whitney's proposal was unsuccessful.Fact|date=July 2008 The GEnx uses some technology from the GE90 turbofan, including composite fan blades. The engine carries composite technology into the fan case.

For the first time in commercial aviation both engine types will have a standard interface with the aircraft, allowing any 787 to be fitted with either GE or RR engines at any time. The engine market for the 787 is estimated at US$40 billion over the next 25 years.

Another first is the elimination of bleed air systems using high temperature/high pressure air from the propulsion engines to power aircraft systems such as the starting, air-conditioning and anti-ice systems. The GEnx and the Trent 1000 allow a move towards the "electric" airplane.

The GEnx is expected to produce thrust from 53,000 to 75,000 lb_f with first tests commencing in 2006 and service entry by 2008 (now delayed by 787 deliveries). Boeing predicts reduced fuel consumption of up to 20% and significantly quieter engines than current turbofans.

A 66,500 lb_f thrust version (GEnx-2B67) will be used on the 747-8. Unlike the initial version, for the 787, this version has a traditional bleed air system to power internal pneumatic and ventilation systems. It will also have a smaller overall diameter than the initial model to accommodate installation on the 747.

Although General Electric was to have supplied a variant of the GEnx for the original Airbus A350, GE has yet to reach an agreement with Airbus to power the redesigned A350XWB. This aircraft is a Boeing 787 and Boeing 777 competitor.

General Electric has a 64% risk-sharing stake in the GEnx program. Other stakeholders include Ishikawajima-Harima Heavy Industries (IHI), 15%, and Avio, 12%. Volvo Aero, Techspace Aero, Mitsubishi Heavy Industries and Samsung Techwin hold the remaining 9%. Notably absent is General Electric's frequent partner, Snecma, historically GE's largest partner on aircraft engine projects. Snecma may still supply parts, however, but is deeply involved with the PowerJet joint venture.

General Electric began initial test runs of the bleedless GEnx variant on 19 March, 2006." [http://www.flightglobal.com/Articles/2006/03/21/Navigation/177/205589/General+Electric+performs+first+run+of+new+GENx+engine.html General Electric Performs First Run of New GEnx Engine] ." "Flight International". March 21, 2006.] The first flight with one of these engines took place on 22 February 2007, using a Boeing 747-100, fitted with one GEnx engine in the number 2 (inboard LH) position.

Technology

Despite being derived from the GE90, the GEnx features a number of weight-saving innovations:
* Fan diameter:111in (2.82m) for the 787-8 and 105in (2.64m) for the 747-8.
* Composite fan blades with titanium leading edges for reduced weight
* Fan case of composite material for reduced weight and expansion
* Titanium aluminide stage 6 and 7 low pressure turbine blades

Fuel burn reduction technologies include:
* Fan bypass ratio of 9.5:1, which also helps reduce noise
* High pressure compressor based on GE90-94B, with 23:1 pressure ratio with only 10 stages
** shrouded guide vanes to reduce secondary flows
* Counter-rotating spools for the reaction turbines to reduce load on guide vanes
* lean premixed combustor to reduce environmentally-harmful emissions
** with improved airflow to prevent back flash

And features to reduce maintenance cost and increase engine life, such as:
* Spools with lower parts count
** by using bliscs in some stages and low blade counts in other stages and by using a low number of stages
* Cooler internal engine temperatures by using more efficient cooling techniques
* debris extraction within the low pressure compressor guards high pressure compressor

All of these yield a fuel burn said to be 15% better than GE's CF6-80C2 engines for widebody aircraft.

Engine selections

Boeing 787

GE-Aviation had a slow sales start on the 787 but has since caught up. In what many consider to be the most significant Boeing 787 order, that of Japan's All Nippon Airways, the Rolls-Royce Trent 1000 was selected as the engine on 13 October, 2004. The Japanese deal was considered vital by both companies due to the size of the order (valued at US$1 billion (£560 million)) and the trend-setting decisions of the carrier. GE & P&W were previously the engines of choice in the Japanese market.

On 27 February, 2007, Qantas announced that they have selected the GEnx for their upcoming Boeing 787 fleet with a total of 45 orders.

From March, 2008, GE had the most engine orders for the 787 with a total of 374 aircraft sets. The Rolls-Royce Trent 1000 has 259. Certification was expected to be achieved in the latter half of 2007." [http://www.aviationnow.com/avnow/news/channel_comm_story.jsp?id=news/aw041706p1.xml GEnx Development Emphasizes Composites, Combustor Technology] ." Meacham, M. "Aviation Week & Space Technology". April 16, 2006.]

Airbus A350

Initially GE-Aviation benefited from being named as lead supplier for the A350 engine, winning early engine orders for 105 A350s (as of June 17 2005) by default. However, on July 17, 2006, Airbus announced a major redesign of the A350, including adding XWB (Xtra Wide-Body) to the name as many airlines considered the old derivative approach of the aircraft uncompetitive with the Boeing 787. Rolls-Royce reached an early agreement with Airbus to supply a brand new variant of the Rolls-Royce Trent, known currently as the Trent XWB for all A350 XWB variants. Meanwhile, GE is in talks with Airbus about offering a version of the GEnx for the A350-800 and -900 XWB. The A350-1000 XWB will not be available with GEnx engines, nor the Engine Alliance GP7000. [http://atwonline.com/news/story.html?storyID=8150]

Boeing 747-8

Boeing has awarded an engine contract for the 747-8 to GE-Aviation to provide the GEnx-2B exclusively.

References

External links

* [http://www.geae.com/engines/commercial/genx/index.html GE GEnx website]
* [http://www.flightglobal.com/articles/2007/02/23/212278/picture-general-electrics-genx-1b-engine-for-the-boeing-787-makes-first-flight-on-747.html First flight with this engine]