FAA Cleen Program May Revive Open Rotor Engines

 - July 5, 2010, 8:58 AM

The FAA awarded five contracts worth a total of $125 million over five years to engine manufacturers and Boeing to “develop and demonstrate technologies that will reduce commercial jet fuel consumption, emissions and noise.” The research is intended to accelerate introduction of green technology in the FAA’s Next Generation air traffic modernization program as part of the agency’s continuous lower energy, emissions and noise (Cleen) program. Participants include Boeing, General Electric, Honeywell, Pratt & Whitney and Rolls-Royce North America, all of which will match the FAA’s investment in the cost-sharing program. The companies will study alternative fuels, lighter turbine engine components, noise-reducing engine nozzles, wing trailing edge technology, optimized flight trajectories and open-rotor and geared turbofans.

Goals of the Cleen program include:

• Fuel burn reduction by 33 percent relative to current subsonic aircraft technology.
• Engine technology that reduces landing and takeoff cycle nitrogen oxide emissions by 60 percent, without increasing other gaseous or particle emissions, over the 2004 International Civil Aviation Organization standard.
• Certifiable aircraft technology that reduces noise levels by 32 dB cumulative, relative to the current Stage 4 noise standard.
• Sustainable alternative aviation jet fuels and safety and transition strategies that enable “drop in” replacement for petroleum-derived aviation fuels with no significant modifications to aircraft and engines required and that perform more efficiently and cleaner than fossil-based fuels.
Cleen technology might be implemented as early as 2015, according to FAA Administrator Randy Babbitt. “Cleen is poised to get advances into service as quickly as possible,” he said. Cleen participants will meet semi-annually and a modeling tool developed by the Georgia Institute of Technology will be used to assess Cleen progress.

Flight tests of adaptive wing trailing edges and ceramic matrix composite acoustic engine nozzles will be flight tested on a Boeing 737 NG in 2012 and a twin-aisle airplane in 2013. Adaptive trailing edges are controllable devices on the aft portion of the wing, according to Boeing, which “can help tailor the wing configuration to reduce fuel burn at takeoff, climb and cruise, and to reduce community noise at takeoff and landing.” Ceramic matrix composites can withstand hotter-running engines and thus “offer the potential of better thermal and structural performance, while helping to reduce weight and acoustic footprint.”

The Taps II combustor in General Electric’s new new eCore engine core will deliver up to 16 percent better fuel efficiency, according to GE, and eCore will be used in CFM International’s new Leap-X engine and for new GE regional and business jet engines. GE will also conduct technology demonstrations of FMS trajectory algorithms to improve fuel, emissions and noise performance and develop capability for an FMS to share information with the FAA’s en route modernization system “to enable the four-dimensional trajectory-based FMS to fly more optimum trajectories.” Cleen funds will help pay for research into blade aero-acoustic and pitch change mechanism research on GE’s open rotor (unducted fan) engine. The design reduces fuel consumption by 26 percent and addresses noise challenges, according to GE, which conducted wind tunnel testing last year on counter-rotating fan systems. The Leap-X engine is a candidate for open rotor technology.

Honeywell is working with Gulfstream Aerospace and the Massachusetts Institute of Technology on further development of its UOP green jet fuel, using the Honeywell Tech7000 engine technology demonstrator. Honeywell UOP’s jet fuel can be made from sources such as algae and camelina (flax), and the fuel meets current specifications while significantly lowering emissions, according to Honeywell.

Pratt & Whitney is continuing development of advanced technologies for its PurePower geared turbofan engine family. By 2020, the company expects to achieve fuel burn savings of 25 to 35 percent. Compared to current engines, the PurePower family offers a 50-percent reduction in noise, according to Pratt & Whitney.