|General Electric GEnx at the Paris Air Show 2009|
|Major applications||Boeing 747-8 |
Boeing 787 Dreamliner
|Unit cost||787-8 GEnx-1B: $25.6 million |
787-9 GEnx-1B: $28.7 million
747-8 GEnx-2B: $22.5 million
|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.
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.
Boeing wanted to allow changing between alternative 787 engines within 24 hours, but had not worked it out by 2007. 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. 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.
Introduced in late 2011 on a 747-8 freighter, Cargolux surpassed one million flight hours in early 2017. In the summer of 2012, three engines suffered Low Pressure Turbine (LPT) failures. One failure was caused by an assembly problem, which led to inspections of all other engines then in service.
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 AirBridgeCargo 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 cited was "'unique convective weather systems' such as unusually large thunderstorms reaching high altitudes." Boeing is working with GE on software solutions to the problem. Altitude was restricted until GE changed the software to detect the high-altitude ice crystals and open bleed air valve doors to eject them before they enter the core.
In March 2014, a GEnx-powered Boeing 787 had its first in-flight shut down in operation when a JAL flight had to divert to Honolulu after an oil pressure alert, bringing its in-flight shut down rate to 1 per 278,000 hours. In January 2016 a Japan Airlines 787 had an inflight shutdown after flying through icing conditions, caused by ice formed on fan blades and ingested: the blades moved forward slightly and rubbed on the abradable seal in the casing. In March 2016, the US FAA ordered emergency fixes on the GEnx-1B PIP2. The airworthiness directive affects 43 Boeing 787 Dreamliners in the US. Abradable material in the casing in front of the fan blades was ground to keep them from rubbing when ingesting ice or debris on 330 GEnx PIP-2.
The GEnx is derived from the GE90 with a fan diameter of 111.1 in (282 cm) for the 787 and 104.7 in (266 cm) for the 747-8. To reduce weight, it features 18 composite fan blades, a composite fan case and titanium aluminide stage 6 and 7 low-pressure turbine blades. Fuel efficiency is improved by 15% compared to the CF6, the bypass ratio reaches up to 9.0:1 and the overall pressure ratio up to 58.1:1. It has a 10 stage high-pressure compressor and is quieter, helped by larger, more efficient fan blades.
It stays on wing 20% longer, uses 30% fewer parts to lower maintenance costs and has a contra-rotating architecture. The Lean TAPS combustor reduces NOx gases with required pressure loss and backflow margin.
Fan blades have steel alloy leading edges and the composite fan case reduces thermal expansion. To reduce fuel burn, the 23:1 pressure ratio high-pressure compressor is based on the GE90-94B, shrouded guide vanes reduce secondary flows and counter-rotating spools for the reaction turbines reduce load on guide vanes.
To reduce maintenance cost and increase engine life, spools with lower parts count are achieved by using blisks in some stages, low blade counts in other stages and by using fewer stages; internal engine temperatures are reduced due to more efficient cooling techniques and debris extraction within the low-pressure compressor protects the high-pressure compressor.
|Fan Diameter||111.1 in (2,822 mm)||104.7 in (2,659 mm)|
|Compressor||1 Fan 4 LP 10 HP||1 Fan 3 LP 10 HP|
|Turbine||2 HP 7 LP||2 HP 6 LP|
|Takeoff thrust||69,800 lbf (310 kN)||74,100 lbf (330 kN)||76,100 lbf (339 kN)||66,500 lbf (296 kN)|
|Takeoff Bypass ratio||9.0||8.8||8.8||8.0|
|Takeoff air per sec.||2,559 lb (1,161 kg)||2,624 lb (1,190 kg)||2,658 lb (1,206 kg)||2,297 lb (1,042 kg)|
|Flange to flange||184.7 in (4,691 mm)||169.7 in (4,310 mm)|
|Nominal RPM||LP 2,560, HP 11,377||LP 2,835, HP 11,377|
|Dry weight||13,552 lb (6,147 kg)||12,397 lb (5,623 kg)|
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