Though the testing process for jet engines is rigorous and can even be rudimentary at times, it is far from mundane.
One of the biggest challenges in the aerospace industry is designing for safety and meeting stringent FAA standards and testing. General Electric (GE) takes its testing seriously. So much so that the company uses what looks like a jet-engine-sized death star. The Sphere of Turbulence, or Turbulence Control Structure (TCS), is essentially a honeycombed, high-tech wind shelter.
There are several components to GE’s Peeples Test Operation that run a grueling set of tests on engines, providing development insight to the rigors that the machines encounter during the design and development process. Every year, GE burns through a reported 10 million gallons of jet fuel simply to test engines.
GE exposes engines to hardships that are far beyond anything encountered in nature. A cell, one of which is a 40-foot tall concrete box, is used to mount an engine from the ceiling and allows engineers to throw anything that they can at it.
Snap acceleration, revving the engine from zero to full throttle in one second, is one of the many tests conducted in the cell. With 20-inch thick walls, engineers test the amount of force the engine puts on the building and convert it to thrust.
The most aesthetically impressive testing (and surely the most miserable of engineering occupations) takes place at GE’s Winnipeg, Canada facility, where engines are put through testing in -8°F weather.
Seven fans, operating with 250 HP each, blow 2,800 pounds of cold air per second at a suspended engine — but that’s not the end of the onslaught. The simulated wind can reach speeds up to 60 mph, giving the engine a proper gale-force experience. Engineers then add thousands of gallons of water via 125 high-pressure nozzles to test the engine’s endurance to icing at both idling and take-off speeds.
GE Aviation media relations, Matthew Benvie explains, “The Canada facility was originally established to handle jet engine cold weather and ice testing, but GE invested $2.5 million in the facility over the past year to incorporate digital temperature-catching equipment, turbulence control structures, and a concrete base to allow the wind tunnel to accommodate different types of testing.”
GE uses the TCS to keep conditions and airflow around a jet engine controlled, so as to get precise measurements of fuel flow and provide a sound testing environment for compressor and turbine deterioration. The Sphere itself is made up of 300 flat aluminum honeycombs and perforated stainless steel plates, spans 32 feet in diameter, and weighs 30,000 pounds.
“In the simplest terms, it’s a wind shelter that allows us to test engines faster because we don’t have to wait,” GE aerospace engineer, Jose Gonsalez says. “The perforated sheet serves to attenuate streak-wise flow unsteadiness, while the honeycomb structure provides transverse flow uniformity.”
The Sphere of Turbulence isn’t the only structure floating around GE’s Peebles Test Operation facility. To help create simulations of everything from minor turbulence to hurricane-force winds, GE employs a 55-foot wind tunnel to put engines through the ringer.
Based on a design originally created by Boeing engineers Ulrich W. Ganz and Paul C. Topness for noise level tests, the Sphere is attached to an engine’s intake for smooth, unaltered airflow. Providing a controlled testing environment is vital for proper FAA certification and component development.
Reducing variation in thrust and fuel consumption data is essential to safety and efficiency testing, and as the company plans to start using biofuels, the data escalates in importance. Gonsalez says in a statement released by the company, “You take wind-induced inlet airflow variation out of the picture. You don’t want that as a variable when you collect performance data across many days under different conditions.”
Before using the TCS, engineers had wait for a calm, clear day, which significantly slowed development. “When there is a lot of sunshine and convective heating from the sun, you can better deal with the variable wind conditions caused by them and expand your allowable wind envelope,” Gonsalez says. “We can run more tests more often.”
Though the testing process for jet engines is rigorous, and can even be rudimentary at times, it is far from mundane.
“There is no official order of testing – it depends on the program. We complete testing on an as available schedule, one test doesn’t need to come before another,” Gonsalez explains.
GE’s engines are reaching record production levels, which has led to the company’s use of multiple TCS structures and investments in other testing equipment to speed the development process.
Matthew Benvie explains, “Overall deliveries of all engine models will rise to more than 1,600 in 2014, compared with over 1,200 in 2012 and 1,400 in 2013. Many of these engines are completely new engines, which is where the TCS dome comes in.”
With the expected increase, GE plans to build more Spheres of Turbulence, as well as other testing components.
Filed Under: Aerospace + defense