GE's next-generation composite turbine blades to improve aircraft fuel efficiency
By David Szondy
September 4, 2014
GE is looking to a new generation of carbon-fiber composites to make the fan blades for its GE9X jet engine. That engine is being developed for the Boeing 777X passenger airplanes that are set to enter service in 2020 and the new blades promise to provide larger, lighter engines with greater fuel efficiency.
Jet engine turbines are wonderfully simple machines when you look at a schematic, but that belies a remarkable underlying complexity. The blades have an intricate shape of complex curves that are hard to manufacture and must stand up to incredible temperatures, pressures, and hot corrosive gases. Even the fan blades of a modern jet engine, which have an easier time of it, are incredibly difficult to manufacture.
Traditionally, fan blades have been made out of metal, but these have their limitations. Composite materials seem a promising alternative, but GE says that even though composite blades are lighter and more durable than metal blades, they need to be thicker. Now the company has come up with a stiffer fiber for the fourth-generation composite that allows the blades to be made in thicknesses similar to that of metal ones. In addition, they are given steel alloy edges instead of titanium for greater strength.
GE says that the new composite allows the fans on the GE9X to have thinner and fewer blades. This means a lighter fan, a lighter engine than the previous GE90 – which is the largest fan in the GE inventory with a diameter of 133 in (338 cm) – and enhances air flow through the engine, resulting in fuel consumption savings of five percent compared to similar engines.
Though this may sound like a straightforward improvement, the GE team had to use a thorough trial and error testing process that they say Thomas Edison would recognize. Thus included coupon testing of static, fatigue and fracturing, as well as ultimate strength.
"The GE9X team is combining the lessons learned from those fielded blades with the next generation of material and aero technologies to push the envelope and maintain our competitive edge," says Tod Davis, the GE9X composite fan blade design leader. "The carbon fiber composite material has also advanced during the past 10 years. The advancements allow us to design a thinner blade, which is just as strong as our current composite fan blades. Fewer, thinner blades will enhance the airflow and make for a lighter, more efficient fan that will help with the GE9X engine’s overall performance and fuel burn."
The GE9X is scheduled to be included in 777Xs purchased by Emirates, Etihad Airways, Lufthansa, Cathay Pacific, and Qatar Airways. GE is currently carrying on with testing with the goal of freezing design next year and flight testing in 2017.