How large is the world’s largest jet engine? So large that a professional basketball player would fit inside it comfortably with several feet to spare. Engineers at GE Aviation just assembled the first of these engines and put it on a test stand at the company’s massive boot camp for jet engines located in the woods near Peebles, Ohio.
It’s a giant.
The brand new GE9X is a winner in several disciplines. Its front fan spans a full 11 feet in diameter (3.35 meters), a world record. The engine also has 3D printed fuel nozzles and the most extensive use of parts made from lightweight and ultra heat-resistant materials called ceramic matrix composites (CMCs).
Additive manufacturing, popularly known as 3D printing, essentially grows parts from the ground up and allows engineers to design complex internal shapes that were previously impossible to achieve. “These tunnels and caves are a closely guarded secret,” says GE Aviation spokesman Rick Kennedy. “They determine how the fuel moves through the nozzle and sprays inside the combustion chamber.”
CMCs operate in temperatures as high as 2,400 degrees Fahrenheit. The material is inside the combustor and the turbine. It allowed engineers to keep the heat higher inside the engine while reducing fuel burn and emissions. “The hotter the engine runs, the more efficient it is,” Kennedy says.
The engine also includes 16 fourth-generation carbon-fiber fan blades at the front of the engine that feed air into an 11-stage high-pressure compressor with a 27:1 pressure ratio, which also boosts the engine’s efficiency. No other commercial engine in service has a pressure ratio that’s higher.
Although this is the first time the company fired up the whole engine, it’s been testing individual components and systems for four years. “Due to the significant amount of new technologies in the GE9X, we planned the testing program differently,” says GE9X program leader Chuck Jackson. “The early testing informed the design and manufacturing and allowed us to freeze the product definition and test the total engine as soon as possible.”
The GE9X was designed to generate 100,000 pounds of thrust. (One space shuttle main engine produces 375,000 pounds.) While that may seem like a lot, the world record belongs to the engine’s predecessor, the GE90-115B, which generated 127,500 pounds of thrust.
When Boeing decided to build the 777X jet, the next-generation version of the 777 jet, it asked GE to develop an engine to power it. GE Aviation, which is the exclusive engine maker for the 777X, has received orders for more than 700 GE9X engines valued at $29 billion (list price) from airlines including Emirates, Lufthansa, Etihad Airways, Qatar Airways and Cathay Pacific.
GE Aviation invested $10 million to prepare its Peebles Testing Operation for the GE9X. Some of the money paid for the largest “bellmouth inlet duct,” the white funnel attached to the front of the engine during testing. It measures 18 feet in diameter and 12 feet in length.
Engineers also installed a fourth fuel tank to keep the engine well fed, fortified the bunker-like test stand to secure the engine and added new material to the testing stand air systems to withstand the high temperatures. “We also upgraded our engine hoists and transporters to handle the GE9X and modified a wall in our prep building so the engine can be moved after final assembly to make its way to the test stand,” said Brian DeBruin, plant manager for GE Aviation’s Peebles Test Operation.
GE Aviation started testing the first GE9X in March and will continue for several months in order to verify aerodynamic, thermal and mechanical characteristics of the engine. The company will start testing the second GE9X next year. The engine is scheduled to enter service by the end of the decade.
By the way, GE also built the first U.S. jet engine in 1942. You can watch that story here.