GE is working on fourth generation composite blades

Nick Kray is a consulting engineer for composite design at GE Aviation. In the 1990s, he was part of a high-stakes gambit to make the front fan of GE’s largest jet engine from epoxy and carbon fibres. “Our competitors make jet engine fans from titanium and steel and even some of our own people weren’t initially so hot about using composites,” Kray said. “Nobody had tried this before.” However, the carbon-fibre composite blades allowed GE’s aerospace engineers to design the GE90, still the world’s largest and most powerful jet engine.

GE is still the only company with composite fan blades in service. They work inside the GE90 and the GEnx engines that power many Dreamliners. The material allowed GE engineers to design blades that result in lighter and more efficient engines, allowing airlines to save fuel by shedding precious pounds.

But they are no longer state of the art. Kray and his team are now busy working on a fourth generation of the blade for the GE9X, GE’s largest engine yet, designed exclusively for Boeing’s next-generation wide-body jet, the 777X.

The team says the blades will feature several new components. Stiffer carbon fibres will be used, meaning the blades can be made longer and thinner. Their trailing edge will be made from a special structural glass fibre composite that can better absorb impact energy. “Carbon fibre is very stiff and not that flexible so that when something hits the blade, it creates a shockwave deep inside it,” Kray explained. “But the glass composite can deform better and deflect stress on the blade.”

GE will also replace the titanium leading edge that is currently used on GE90 and GEnx blades with steel. “It’s a strong material that allows us to keep the new blade thin in shape to maximise performance,” he said. “If you are an aero guy, thinner is always better. We want the best performance that’s humanly possible.”

Where the GE90 has 22 blades and the GEnx has 18, the GE9X will have just 16, even though it is the largest of the three engines with a fan diameter of 134 inches.Besides making the engine lighter, the fewer and thinner blades will also spin faster, giving greater overall engine performance.

In December 2002, the GE90-115B version of the engine achieved a Guinness World Record as the most powerful jet engine ever built, generating thrust in excess of 127,000 pounds – more than early space rocket engines. In 2005, a GE90-powered Boeing 777 set another world record for distance travelled non-stop by a commercial jetliner. The plane covered 11,664 nautical miles between Hong Kong and London in 22 hours and 42 minutes. In 2007, the Museum of Modern Art in New York included the curved composite blade in its design collection.

“Next-generation composites will go even further,” Kray exclaimed. “We are never going back to metal.”

Tom Austin-Morgan

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If you look at Sir Geoffrey Owen's book "The rise and fall of great companies: Courtaulds and the re-shaping of the man-made fibres industry" page 8 in the draft version you will see that Rolls Royce developed turbo fan compressor blades for the RB111 to "steal a march on its two American rivals, General Electric and Pratt & Whitney" These new engines were used to power Lockheed's wide bodied airline, Tristar. After initial euphoria it came as a huge shock when Rolls Royce realised the blades disintegrated with bird strick. Lockheed's subsequent claims against Rolls Royce for late delivery resulted in a financial crisis in Rolls Royce and the UK government taking them over. This was 1969 and someone had tried it before - 25 years earlier!

Comment David Service, 22/04/2016

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