General Electric GEnx

GEnx
General Electric GEnx at the Paris Air Show 2009
Type	Turbofan
Manufacturer	GE Aviation
First run	2006
Major applications	Boeing 747-8 Boeing 787 Dreamliner
Developed from	General Electric GE90

The General Electric GEnx (General Electric Next-generation) is an advanced dual rotor, axial flow, high-bypass turbofan jet engine in production by GE Aviation for the Boeing 787 and 747-8. The GEnx is intended to replace the CF6 in GE's product line.

Design and development

GEnx on 747-8I prototype

The GEnx and the Rolls-Royce Trent 1000 were selected by Boeing following a run-off between the three big engine manufacturers. The GEnx uses some technology from the GE90 turbofan, including composite fan blades, and the smaller core featured in earlier variants of the engine. The engine carries composite technology into the fan case.

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.^[1][2] The engine market for the 787 is estimated at US$40 billion over the next 25 years. A 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. Both engines enable the move towards the More Electric Aircraft, that is, the concept of replacing previously hydraulic and pneumatic systems with electrical ones to reduce weight, increase efficiency, and reduce maintenance requirements.

The GEnx was expected to produce thrust from 53,000 to 75,000 lbf (240 to 330 kN) with first tests commencing in 2006 and service entry by 2008 (delayed by 787 deliveries). Boeing predicts reduced fuel consumption of up to 20% and significantly quieter engines than current turbofans. A 66,500 lbf (296 kN) 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.

General Electric began initial test runs of the bleedless GEnx variant on 19 March 2006.^[3] 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 left hand side) position.

Technical problems

In the summer of 2012, three engines suffered Low Pressure Turbine (LPT) failures; one was caused by an assembly problem, which led to inspections of all other engines then in service.^[4] During the spring and summer of 2013, GE learned of four 747-8F freighters that suffered icing in their engines at altitudes of 40,000 feet and above. The most serious incident involved an AirBridge Cargo freighter. On July 31, while at an altitude of 41,000 feet over China, the flight crew noted two engines surging while a third lost substantial power. The pilots were able to land the plane safely, but the engines were found to have sustained damage. Among the possible factors GE cited in an interview with the Wall Street Journal was "'unique convective weather systems' such as unusually large thunderstorms reaching high altitudes."^[5] Boeing told the newspaper that it is working with GE on software solutions to the problem.^[5]

In March 2016, the Federal Aviation Administration of the United States ordered emergency fixes on the GEnX-1B PIP2 turbofan engine system, due to issues met on in-service aircraft flying in icing conditions.^[6] The airworthiness directive affects 43 Boeing 787 Dreamliners in the US, and other nations are expected to follow suit. The fix involves using fan-grinding machinery.^[7]

Technology

Fan blades and inlet guide vanes of GEnx-2B

Detail of GEnx core

Despite being derived from the GE90, the GEnx features a number of weight-saving features:

• Fan diameter of 111 in (2.8 m) for the 787-8 and 105 in (2.7 m) for the 747-8.
• Composite fan blades with steel alloy leading edges.
• Fan case of composite material which reduces weight and thermal expansion.
• Titanium aluminide stage 6 and 7 low-pressure turbine blades.

Fuel burn reduction technologies include:

• Fan bypass ratio of 9.6:1, which also helps reduce noise.
• High-pressure compressor based on GE90-94B, with 23:1 pressure ratio and only 10 stages. Also, shrouded guide vanes reduce secondary flows.
• Counter-rotating spools for the reaction turbines to reduce load on guide vanes.
• Lean TAPS (twin annular premixed swirler) combustor to reduce environmentally-harmful emissions with improved airflow to prevent back flash.^[8]

Among features to reduce maintenance cost and increase engine life are:

• Spools with lower parts count achieved by using blisks in some stages and low blade counts in other stages and by using a low number of stages.
• Internal engine temperatures reduced 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.

Applications

• Boeing 747-8
• Boeing 787 Dreamliner

Specifications

Data from.^[9][10]

This engine is a dual rotor, axial flow, high bypass ratio turbofan. The 10-stage high-pressure compressor is driven clockwise (Aft Looking Forward) by a 2-stage high-pressure turbine. The single-stage fan and 4-stage low-pressure compressor are driven counterclockwise (Aft Looking Forward) by a 7-stage low-pressure turbine. The engine control system includes a Full Authority Digital Engine Control (FADEC), which has an aircraft connection for digital communication. An engine monitoring unit (EMU) provides vibration level signals to the aircraft.

Notes:

• Data for sea level static, standard pressure, no customer bleed or customer horsepower extraction, ideal inlet, 100% ram recovery, production aircraft flight cowling, production instrumentation, fuel lower heating value of 18,400 BTU/lb.
• The 787-3 variant was cancelled in December 2010 due to low demand by customers.^[11]

Specifications (GEnx-1B64)

Rear view of a GEnx-1B on a Jetstar 787-8, showing noise-reducing chevrons

Data from ^[12]

General characteristics

• Type: Turbofan
• Length: 4.69 m (184.7 in)
• Diameter: 2.82 m (111.1 in)
• Dry weight: 5,816 kg (12,822 lb)

Components

• Compressor: Axial, 1 stage fan, 4 stage low pressure compressor, 10 stage high pressure compressor
• Combustors: Annular
• Turbine: Axial, 2 stage high pressure turbine, 7 stage low pressure turbine

Performance

• Maximum thrust: 284 kN (63,800 lbf)
• Overall pressure ratio: 41
• Thrust-to-weight ratio: approx 5:1

See also

Related development

• General Electric GE90

Comparable engines

• Engine Alliance GP7000
• Rolls-Royce Trent 1000
• Rolls-Royce Trent XWB

Related lists

• List of aircraft engines

References

External links

Wikimedia Commons has media related to General Electric GEnx.

• GE GEnx website
• First flight with this engine
• FAA Type Certificate