GE Aviation engineers are developing a new class of materials called ceramic matrix composites (CMCs) that they say will allow construction of more powerful and efficient jet engines before the end of the decade.

GE is testing CMC parts inside engines for passenger planes as well as fighter jets. Image credit: GE Aviation.GE is testing CMC parts inside engines for passenger planes as well as fighter jets. Image credit: GE Aviation.These so-called “super ceramics,” which GE has been developing for two decades, are as durable as metals, according to the company, but are two-thirds lighter and can operate at 2,400 degrees Fahrenheit—500 degrees higher than other advanced alloys. These properties allow engineers to design lighter components for engines that do not require as much cooling air and still generate more power and burn less fuel.

As the name implies, composite materials like CMC are made from separate materials, which are then joined together. GE fabricates CMCs from silicon carbine fibers embedded in a silicon carbide matrix. The fibers are thinner than human hair and covered with a proprietary coating that produces a material that is tough like a metal but not brittle like a ceramic.

CMCs could allow designers to increase jet engine thrust by 25% and decrease fuel consumption by 10% by 2020, according to Dr. Sanjay Correa, who heads the GE's CMC program.

Earlier this year, GE started testing CMC components in a GEnx engine—the type used by many Boeing 787 Dreamliners—to develop the technology for its newest large engine; the GE9X. When completed, the GE9X engine will be one of the largest jet engines ever built, with an 11 foot-in-diameter fan and a capability of 60:1 air compression.

While these numbers hold promise, CMCs historically have been difficult to mass-produce, limiting their use to the space industry and fighter jet exhaust systems.

Starting in 2000, GE’s Oil & Gas business tested CMCs inside a 2 megawatt gas turbine in Florence, Italy. By the middle of the decade, turbines with CMC shrouds—special parts directing the flow of air into the hottest parts of the machines—were running for thousands of hours without incident.

GE’s aviation business picked up the technology in 2007 and started looking for jet engine applications. GE Aviation first used the material for CMC shrouds in the hot section of its F-136 fighter jet engine, and the application quickly spread. Static CMC parts are now flying inside the next-generation passenger LEAP engines developed by CFM International, a joint venture between GE and France’s Snecma (Safran).

GE researchers have now started replacing rotating metal components with CMCs. Reducing their weight by two thirds, GE says, would produce a knock-on effect by lowering the centrifugal force inside the engine—allowing designers to reduce the size of the engine’s main shaft and cut engine weight further.

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