General Electric and Rolls-Royce North America’s LibertyWorks will both proceed into Phase 2 of the U.S. Air Force Research Laboratory’s Adaptive Versatile Engine Technology (ADVENT) demonstration program, but funding constraints mean only Rolls will build and test a full engine.

A flagship effort under the Versatile Affordable Turbine Engines (VAATE) program, ADVENT is developing technology for an adaptive turbofan able to combine high thrust for supersonic speed with low fuel burn for subsonic endurance.

Both GE and LibertyWorks successfully completed Phase 1 of ADVENT, says Larry Burns, VAATE program manager, adding: “We determined both companies had uniquely different configurations, both capable of meeting the ADVENT goals.”

The issue was funding. “There is not enough currently available to allow both contractors to do full TRL [technology readiness level] 6 demonstrations,” he says. “That forced us to select one to do the complete demonstration.”

GE has been funded to demonstrate the complete core engine and perform risk-reduction rig tests on its adaptive fan. The award “allows critical items to move along so they could still do a full demonstration” if funding was found from elsewhere, Burns says.

“The core engine has the highest technologies and a big part of an adaptive engine is the fan,” he says. “GE has been funded to develop its adaptive fan and core and wring out the bulk of the risk so it’s possible to integrate them into a full demonstrator.”

Budget changes will delay the first run of LibertyWorks’ ground-demonstrator engine by about six months, to 2013, according to Burns, who believes the adaptive technology could still be incorporated into production engines available in the 2018-2020 timeframe.

ADVENT will vary fan airflow and pressure ratio to optimize specific fuel consumption and thrust over the entire operating range. It also will capitalize on industry investment in next-generation commercial cores to provide the best thermodynamic cycle, Burns says.

LibertyWorks was picked to do the full engine demonstration after a complete evaluation of both ADVENT designs. “The capability to do the full engine demonstrator is wholly contained within Rolls-Royce North America,” Burns stresses.

Image: USAF