Dwight “Ike” Eisenhower claimed that whenever he ran into a problem, he’d “always make it bigger” to see the outlines of a solution. But you don’t need to be a U.S. president to believe that bigger is better. German engineer Christian Aalburg, who works for GE Global Research in Munich, says that seeing things on a larger scale allows him to build better jet engines.
Jet engines and gas turbines operate on a four-step process that Aalburg’s collegue Todd Wtzel summarized — a bit tongue-in-cheek — as, “suck, squeeze, bang, blow.” First, Wetzel says, the engine’s fan sucks in massive amounts of air. Next, a compressor squeezes it like a bicycle pump. This progression brings air molecules closer, making the air hotter and its volume smaller and causing it to bang when mixed with fuel in the combustor. Finally, the combustor blows the air out through the turbine, pushing the plane forward or powering an electric generator.
Above: Engineer Marcel Schmieder is preparing to run a test on the new compressor rig. Image credit: Uli Benz / TU Munich. Top image: the new rig will help develop new compressors for machines like the gigantic GE9X jet engine, here featured at GE Aviation’s test stand in Peebles, Ohio. Image credit: GE Aviation
Today’s jet engines like the GE9X— the world’s largest jet engine — already compress air up to 60 times, and they will have to squeeze it even more to improve efficiency further. That, however, creates a host of aerodynamic, thermal and mechanical challenges. “If we compress the air to make it smaller and smaller, the blades in the compressor get smaller and smaller and temperatures get hotter and hotter,” Aalburg says. This could spell mechanical trouble down the road.
Aalburg manages the turbomachinery aerodynamics group, which is only a 5-minute walk from the High-Speed Research Compressor lab, operated by GE with the Technical University Munich — one of the world’s most advanced compressor labs. There, with his team, he is creating a new test facility that will test massive compressors and new aircraft engine concepts for GE’s Aviation, Power and Oil & Gas businesses. The new lab was created with EUR 15 million from TU Munich, GE and the government of Bavaria.
Aalburg and his team have started building supersized test compressors that will be 50 percent larger than those in the GE90 jet engine — the world’s most powerful jet engine with an 11-foot fan that’s as large as the cross section of an entire Boeing 737. The large scale will allow them to see more clearly how small parts work and interact aerodynamically and make better measurements. “Things become easier when we scale up and increase the size of machines,” he says.
Engineer Marcel Schmieder is observing data coming from tests on the compressor rig. Image credit: Uli Benz / TU Munich
Once the team figures out how to make the XXL version more efficient, Aalburg says, making the new engine smaller is as simple as building a smaller-scale model that has precisely the same proportions as the larger research machine.
Because the facility is located on a school campus, Aalburg is about to work shoulder to shoulder with the next generation of engineers and researchers, which, he says, has its advantages. “Students solve things in a much easier way than we might think of,” he says. “They come up with smart and cost-effective ways to do things.”
GE is working to improve fuel efficiency and reduce emissions by as much as possible with the next generation of jet engines. The company’s engineers and researchers already have made huge advances on the campus of TU Munich. For example, they made compressor improvements that helped develop a 1,300-shaft-horsepower turboprop engine that burns 20 percent less fuel and delivers 10 percent more power than comparable engines. The engine, which includes a number of complex 3D-printed components, will be used in the next generation of business aircraft, such as Cessna’s Denali.
If Aalburg and his colleagues can make similar advances in efficiency for commercial jet engines, the payoff will be huge. GE estimates that a 1 percent reduction in jet fuel use could save the global commercial aviation industry $30 billion over 15 years.