General Electric GEnx

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The General Electric GEnx (General Electric Next-generation) is an advanced turbofan under development by GE Aviation for the Boeing 787. After the initial unveiling, GE Aviation decided to also offer the engine for the Airbus A350 and Boeing 747-8. The GEnx is intended to replace the CF6-80C in GE's product line.

1 History and description
2 Technology
3 Engine selections
4 References

[edit] 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, possibly due to having been an all-new, and thus untested, design. The GEnx uses some technology from the GE90 turbofan, including composite fan blades and composite 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 a GE or RR engine at any point in time. Engine interchangeability makes the 787 a far more flexible or liquid asset, allowing airlines to change from one manufacturer's engine to the other's in light of any future engine developments or when acquiring 787 from other operators/lessors. 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, which use high temperature/high pressure air from the engine to power aircraft systems, e.g. 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 of 55,000 to 75,000 lb_f (245 to 334 kN) with first tests commencing in 2006 and service entry by 2008. While Boeing predicts reduced fuel consumption of up to 20% the 787's engines are also expected to be significantly quieter than current turbofans.

A 66,500 lbf thrust version (GEnx-2B67) will be used on the 747-8. This version includes a traditional bleed air take-off system.

Although General Electric was to have supplied a variant of the GEnx for the original Airbus A350 derivative proposal, GE has yet to reach an agreement with Airbus to power the all-new A350XWB proposal. This aircraft, which replaces the earlier proposal, is intended as a Boeing 787 and Boeing 777 competitor. Rolls-Royce is about to develop yet another version of the Trent for this application.

General Electric has a 64% risk-sharing stake in the GEnx program. Other stakeholders include Ishikawajima-Harima Heavy Industries (IHI) at 15% and Avio at 12%. Volvo Aero, Techspace Aero, and Mitsubishi Heavy Industries hold the remaining share. Notably absent is General Electric's frequent partner, Snecma, which has historically been 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 March 19, 2006.^[1]

[edit] 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 104in (2.64m) for the 747-8.
Composite fan blades with titanium leading edge
Fan case also made of composite material

Fuel burn reduction technologies include:

Fan bypass ratio of 9.5:1 which also reduces noise
High pressure compressor based on that of GE90-94B, pulling 23:1 pressure ratio
Counter-rotating spools
Combustors with improved internal airflows which also reduces environmentally-harmful emissions

And features to reduce maintenance and increase engine life such as:

Spools with lower parts count
Cooler internal engine temperatures using more efficient cooling techniques

All these should yield a fuel burn of at least 15% better than GE's CF6-80C2 engines for widebody aircraft. It is available in both normal bleed configurations and bleedless configurations (as in Boeing 787).

[edit] Engine selections

[edit] Boeing 787

GE Aviation had somewhat of a slow sales start on the 787, but has since caught up. In what many consider to be the most significant 787 order, that of Japan's All Nippon Airways, the Rolls-Royce Trent 1000 was selected as the engine on October 13 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 & PW previously dominated engines sales to the Japanese market. As of Sept 2006, GE currently is the market leader for the 787. Certification is expected to be achieved in the latter half of 2007.^[2]

[edit] 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 A350XWB variants. Meanwhile, GE has confirmed that the A350-800 will be offered with a GEnx variant, and is in talks with Airbus about offering it on the A350-900. The A350-1000 will not be available with GEnx engines.