Alex Hills developed a passion for 3D printing like most hobbyists: He bought a printer and began “tinkering around” with some simple print builds.
A decade ago, Hills, who works as a test hardware engineer at GE Aviation, printed his first generic jet engine design from plans he found online. “It was a real simple model that spun with some bearings,” he says. “I thought it was cool and printed another one that I put on my desk.”
The degree of difficulty of his projects rose along with his skills. He spent six months building a pair of six-foot Saturn V rocket replicas for the National Museum of the United States Air Force in Dayton, Ohio. “I’ve been a volunteer there for 14 years and have been coming up with STEM projects for education and family events,” he says. “That project gave me a lot of experience and technique.”
He’s gotten so good over the years that he can now bring this experience to work, including in some of the most advanced projects. In June 2021, he watched a detailed video about CFM International’s newly announced RISE technology demonstration program, which aims to develop technology for engines as much as 20% more fuel-efficient than the most advanced engines currently in service. (CFM is a 50-50 joint venture between GE and Safran Aircraft Engines.
One component of the RISE project is the open-rotor concept — an idea that keeps the engine fan blades on the outside of its body rather than covered, as is common with jet engines today. The design could lead to fans with diameters as large as 12 feet and potentially dramatically increase the engine’s efficiency. “I wanted to build something that represents what I’ve worked on,” he says. I thought it would be great to build an actual model of the open fan, so I began reverse-engineering the design in software for 3D printing.”
Hills never printed a project without plans prior to this endeavor, let alone an architecture that was so challenging. But the video helped him piece together instructions for his printer. “The video gives you straightforward images of the concept. I roughly scaled things on how big the engine would be based on what information was out there. I was able to develop a model from that,” he says.
Hills worked on the fan first. “It’s a real interesting fan,” he says. The fan blades of even the most advanced jet engines remain at a fixed pitch — kind of like the blades inside the fan you have at home. But the RISE project is seeking to change that. “For this engine, since it’s unducted, to get reverse thrust capabilities you have to pitch these blades, and you can see they rotate on the hub. That’s something that is used on turboprops. It was a challenge.”
After many hours of toying with dimensions and generating a design, Hills finished his first open-fan model last fall. Instead of displaying it on his desk, he donated it to GE’s Cincinnati-based Community Service Fund, and the model was auctioned off for $900.
Word of Hills’ feat spread quickly through the company, all the way to Chris Lorence, chief engineer and general manager for GE Aviation. Lorence, who was preparing for an industry sustainability conference in Europe, was looking for a prop that would easily communicate to his listeners what the advanced open fan was. Sure, there were videos to illustrate the concept, but once he saw Hills’ model, Lorence knew he had found a solution.
Hills turned on his printer, and 10 days later he handed Lorence a new model, just in time for his trip. “The paint was still drying!” Hills laughs.
At the conference, the model performed as designed. “It turned out to be a great way to let people see what we are talking about with these technologies,” Lorence says. "Pictures and videos are just not the same as the tactile element of being able to get up close to a model of the engine to see what we are talking about, particularly something as innovative as the RISE open fan, which is so different from what we’ve done historically in the industry.”
Hills keeps refining his models. His latest tweaks include magnetic, removable rotor blades, a gearing mechanism for the stators and fan blades, and a more detailed core of the engine concept with LED lights. He even pairs the finished product with jet engine sound recorded from a GE90 — the most powerful commercial jet engine in service — starting up and shutting down. Eventually, Hills plans to design a pylon attachment that would hook onto a wing model.
“One of the great things about Alex and the engineering team here at GE is they have such a passion for our product,” Lorence says. “It goes beyond the design work and the day-to-day challenges. People here get very excited about inventing the future. Alex is a great example of how that enthusiasm can reach beyond the workplace."