At the Farnborough Air Show in the UK, CFM International (CFM), a 50/50 joint venture between Snecma (SAFRAN Group) and General Electric Company, introduced LEAP-X (Leading-Edge Aviation Propulsion), an entirely new baseline turbofan engine for current narrow-body aircraft that offers up to a 16% reduction in fuel burn.
In parallel, the company is also working on an open rotor engine that would deliver even greater fuel efficiency benefits.
The first full LEAP-X demonstrator engine is scheduled to run in 2012, and LEAP-X could be certified by 2016. CFM says that the new turbofan will reduce the engine contribution to aircraft fuel burn by up to 16% compared to current CFM56 Tech Insertion engines that power Airbus A320 and Boeing Next-Generation 737 aircraft. Additional fuel burn improvements will be achieved once this engine is paired with new aircraft technology.
A large contributor to the increased fuel efficiency of the engine is an all-new composite fan blade produced with three-dimensional, woven resin transfer molding (3-DW RTM) technology that dramatically reduces engine weight while providing a more durable blade. The new composite technology enables a reduction in engine weight by approximately 400 pounds and in the fan blade count by 25% (from 24 to 18).
Development of ceramic matrix composite (CMC) technology has been underway at GE for more than 25 years. This ultra-light-weight material can support the extremely high temperatures found in the high-pressure turbine. Titanium-Aluminide (Ti-Aluminide), a lightweight alloy that has been under development for the past 20 years, will also be incorporated into the engine.
In late 2008, CFM will perform a series of full-scale fan demonstrator engine tests with the 3-DW RTM fan blades being developed as part of Snecma’s MASCOT program. The engine will complete performance ground tests at Snecma facilities in Villaroche, France, before being transported to GE’s outdoor test facility in Peebles, Ohio, for acoustic and crosswind testing.
The first full core is scheduled to begin testing next year. Hardware for the core, which features an eight-stage compressor (compared to nine in the current CFM56) and single-stage turbine, is being produced now and the core is targeted to fire by mid-2009. A second core test is also planned. The combustor is an advanced version of the TAPS design. (Earlier post.)
|The GE36 unducted fan (open rotor). Click to enlarge. Source: GE|
Open rotor. An open rotor engine is a modified turbofan, with the fan blades placed outside the engine nacelle. Last seriously explored in the 1980s, the open rotor prototypes (such as the GE36 from General Electric) delivered a 30%+ increase in fuel efficiency. Noise, vibration, size and maintenance were issues with the open rotor concepts at the time.
With current progress in modelling and design, however, air engine manufacturers are again looking at this approach. In May, Aviation Week reported that GE and NASA were reviving studies of the abandoned GE36 unducted fan.
Under the cost-sharing Space Act deal with NASA, GE will refurbish all the original unducted fan (UDF) test rigs, and, with the agency, will begin a rigorous analysis of data collected during the $1.2-billion propfan program that ended almost 20 years ago. “We will then be looking at all the new technology that can be added to the system that ran back then, and at what the core would be like, the materials properties of the blades and the fan shapes,” according to GE.
The thrust of the open rotor study, which is still in the stages of being refined, is to overcome noise and mechanical complexity—two major hurdles that stymied the original propfan projects.
CFM is currently conducting studies in four areas for the open rotor configuration: fan aerodynamics and acoustics; mechanical design, including a pitch change mechanism; aircraft installation; and certification methodology. Technology demonstration tests begin next year and will extend through 2011.
When we launched the LEAP56 technology development program in 2005, fuel was at $1.30 a gallon. Today, airlines are paying nearly $4.00 a gallon. Our customers are hurting and we are responding. LEAP56 is the single largest investment in technology in our history; we are bringing the full technical and financial resources of our parent companies to bear to give them a solution: LEAP-X. We have set aggressive targets for this engine, and the technology plan is in place to achieve them.
We are excited about this new engine, but we also think we need to remain flexible. If fuel prices continue to rise, we will need to raise the bar even higher and introduce even more advanced technology. For the next three years, we are pursuing parallel paths: the LEAP-X advanced turbofan and the open rotor. The foundational technologies support either architecture, and we are making good progress toward finding solutions for the inherent technical challenges of an open rotor configuration.—Eric Bachelet, CFM President and CEO