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Jet engine can switch between high thrust and 'economy' modes

26 February 2013

GE engineers are working on a novel new jet engine core design called 'ADVENT', which makes use of new, high temperature ceramic matrix composites.

The new engine core, shown here under development, could help improve fuel efficiency by as much 25 percent, GE claims

“It’s pure thermodynamics,” says Rick Albrecht, manager for advanced military systems at GE Aviation. The higher the temperature inside the engine core, the more efficiently the engine runs. GE engineers believe their new core, in combination with other design changes, could improve fuel efficiency by as much 25 percent, extend flying ranges by 30 percent, and boost thrust up to 10 percent, compared with the performance of current engines.

Raising the heat inside a jet engine is a tricky business. Combustion temperatures are higher than the melting point of even the most advanced aviation alloys. As a result, jet engine designers had to come up with elaborate ways to prevent melting, by 'bleeding' air through tiny cooling ducts within the turbine blades. 

Scientists at GE Global Research have developed new lightweight and heat-resistant materials called ceramic matrix composites (CMCs) that retain their integrity at temperatures in excess of 1,300 degrees Celsius - somewhat above the operating point of even the most advanced superalloy turbine blade materials. Since the new jet engine core has CMC parts inside, it can operate at a higher temperature and therefore develop more power efficiently.

GE's new jet engine combines the fuel economy of the latest engines for passenger aircraft (high-bypass turbofans) with the raw power of military jets. GE and the US Air Force Research Laboratory call this engine design ADVENT, short for ADaptive Versatile ENgine Technology.

The idea for the concept dates back to the 1970s, when Gerhard Neumann realised that he could manage engine performance by controlling the amount of air that flows through the engine core. More flow through the core results in more thrust; less flow in the core saves fuel (airlines prefer this latter design).

ADVENT can automatically switch between the two modes and give fighter pilots the speed they need during combat, and save fuel while cruising home at a slower pace.

Applications for the new core go far beyond the military, however. “The latest GE jet engines like the LEAP, the GE9X, and even the GEnx are looking at an extensive use of CMCs,” says Dave Jeffcoat, ADVENT project manager at GE Aviation. “The tests show that we’ve picked the right technology. We are building on a solid foundation.”


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