Sphere of Turbulence: What’s Hiding Inside a Mysterious Orb at GE’s Jet Engine Boot Camp?

March 7, 2014

Hiding deep in the foothills of the Appalachian Mountains in southern Ohio is a boot camp for some of the world’s most powerful jet engines.

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The Peebles Test Operation is where GE subjects its engines to groaning trials that involve hail and ice blasts, hurricane-force winds, bird strikes and other extreme hardships that exceed anything they are likely to encounter in service.

The tests reflect the tough requirements the U.S. Federal Aviation Administration and other regulatory agencies impose on jet engines before they are certified for commercial service.

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One of the strangest structures at the 7,000-acre facility is a grey, honeycombed orb spanning 32 feet in diameter. Up close, the mysterious sphere appears like a translucent alien beehive attached to the front of a jet engine. The sphere is made from an array of 300 flat aluminum honeycombs and perforated stainless steel plate panels of varying sizes, and weighs 30,000 pounds.

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Meet the “turbulence control structure.” GE owns three of them. The orb is really a high-tech wind shelter. It helps crews smooth out the flow of air into a jet engine during simulations of engine distress, including changes in fuel flow and “deterioration” of the engine compressor and turbine.

Aerospace engineer Jose Gonsalez, who came to GE from NASA, has been testing jet engines at Peebles for seven years.

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The dome is made from an array of 300 flat aluminum honeycombs and perforated stainless steel plate panels of varying sizes.

He says that the dome makes the test site more efficient. It allows him to manage changes in airflow cause by the weather. “You don’t want that as a variable when you collect performance data across many days and under different conditions,” Gonsalez says.

GE first introduced the sphere in the 1990s, when it started testing the world’s most powerful engine, the GE90.

“Before the turbulence control structure, you would have to wait for calm conditions to be within your wind envelope, typically from dusk through early morning,” Gonsalez says. “Now when there is a lot of sunshine and convective heating from the sun, you can better deal with the variable wind conditions. We can run more tests more often.”

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The orb spans 32 feet in diameter and weighs 30,000 pounds.