General Electric and Rolls-Royce reveal more on how they plan to meet Boeing's stringent environmental targets

New details of the General Electric and Rolls-Royce engine bids for the proposed Boeing 7E7 have emerged in the run-up to an expected decision by the airframe maker in November.

GE's bid, based on its GEN-X (Generation-X) programme, will incorporate a lightweight composite fan case, high-flow swept composite fan, integral vane frame, single annular TAPS (twin annular pre-swirl) combustor, and an "ultra low-solidity", low-pressure (LP) turbine.

The engine, which will be based on a scaled GE90 core, will also use the bigger powerplant's load reduction fan de-coupling device, the high-torque capablility GE1014 fan mid-shaft material and a high-flow, swept composite fan based on the GE90-115B design.

The high-pressure compressor will have rebalanced loading in the front and middle stages and tip clearance optimisation.

"It will take us a series of core tests to get there," says GE advanced engines programmes general manager Mike Benzakein. Speaking at last week's International Symposium on Air Breathing Engines meeting in Cleveland, Benzakein said that the GEN-X HPC goal is roughly a 2.5% efficiency improvement in compressor performance.

GE is also working to meet Boeing's aggressive environmental targets. These include 26EPNdB below Stage 3, nitrous oxide (NOx) emissions 60% below ICAO CAEP/ Chapter 4 limits and, relative to the CF6-80E1-powered A330, around 15% lower fuel burn. The GENX goal is less than 4 litres/1,000kg (1USgal/450lb) of NOx at an overall engine-pressure ratio of about 47:1.

"We are also close to the goal of a 1% improvement in specific fuel consumption, and with GEN-X have already achieved 7.3% relative to the GE90," he adds.

R-R has provisionally dubbed its 7E7 proposal the RB262, and expects the final bypass ratio to be between 10.5:1 and 11:1. R-R director of engineering and technology Mike Howse says design optimisation will be improved by Boeing's no-bleed goal for the aircraft.

"By not taking the bleed off the core of the engine it allows us to change the matching of the HP and LP compressors, and we are now almost certain to make the IP [intermediate] counter-rotating," he says.

Few details of Pratt & Whitney's cleansheet design, dubbed PW-EXX, have emerged and it is not known if the company is considering geared fan technology for the bid.

Source: Flight International