It is August 2016, and the US Army has granted GE and the Advanced Turbine Engine Company - a joint venture between Honeywell and Pratt & Whitney - 24-month contracts to take their proposed engines for the Boeing AH-64 Apache and Sikorsky UH-60 Black Hawk military helicopters through preliminary design review. By April 2018, it is time for demonstrations.
One of the key requirements of the contract, in addition to power increases of, say, 50%, and fuel consumption reductions of, say, 25% was that the new engines fit inside the existing airframes. To successfully validate its engine design fit correctly in the helicopters, GE leveraged its polymer 3D printing lab at its Additive Technology Center (ATC) in Cincinnati to develop a printed prototype of its T901 engine true to size.
GE’s T901 engine includes numerous technological advancements that were successfully demonstrated in this rig and engine testing phase, which led the US Army to award GE with a 517 million USD contract that will allow it to flex its metal additive manufacturing (AM) muscle once again. Engineering and manufacturing of several additive metallic T901 engine components is progressing well. The first development engine ran in 2022 and the first flight test engines are now scheduled to be delivered by the fall of 2023.
In March, on a tour of GE Aerospace’s ATC in Cincinnati, TCT was given some context behind the T901 AM applications for the Apache and Black Hawk platforms. Here is GE Aerospace’s AM journey, application by application.
The first FAA approved 3D printed part
“It all started with this one part,” is the line GE likes to use to refer to its 3D printed LEAP fuel nozzle tip. And while this tip – with its 25% weight reduction and 30% cost efficiency increase – did kickstart the company’s additive manufacturing voyage, it was the quick turnaround of the GE90 T25 sensor housing that brought the first FAA-approved 3D printed part eight years ago.
The part needed to undergo a redesign, so the ATC was enlisted to use additive manufacturing to quickly develop and industrialise a new solution. Ten parts were consolidated into one, and 12 units were printed in a single build. Approximately 400 of these components were manufactured and installed on the GE90-94B engines.
Over 180,000 3D printed LEAP fuel nozzle tips have now been shipped, with 1,000 units manufactured every week at GE's Auburn manufacturing facility.
“We needed to do it quickly and be able to iterate fast, which is why we used 3D printing,” ATC Site Leader Chris Philp says.
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T25 sensor housing, GE’s first FAA-approved 3D printed part. The sensor provides pressure and temperature measurements for the GE90 engine’s control system
Heat exchangers
After enhancing the T25 sensor housings, similar design concepts were quickly applied to heat exchangers, with significant reductions applied to part assembly, size, weight, and cost. On the GE9X engine, for example, GE has incorporated an aluminium F357 heat exchanger manufactured on the Concept Laser M2 that is 40% lighter. It also boasts a part consolidation of 163 traditionally manufactured components into a single printed piece.
“A [conventional] heat exchanger has a lot of tubes welded together and we've 3D printed it as a solid body,” Philp explains. “So, it's a lot more durable and has less source of failures.”
A new application
Having proved to the FAA it could additively manufacture reliable aircraft parts, GE was buoyed. As it stepped into its GE9X engine platform, it saw the opportunity to leverage 3D printing in its new engine. The team decided to apply additive manufacturing to a flowpath component, that could otherwise not be produced conventionally within the constraints of the engine.
In doing so, GE designed a cyclonic inducer component which uses centrifugal forces to ‘divert particles of dust to the outside of the flowpath, before being ingested into the main stream, improving durability,’ per Philp.
GE was so confident in the additive design of this component that it had developed its engines with the part in mind before FAA certification was granted. This component is manufactured on the Concept Laser M2 system in a cobalt-chrome alloy and has been consolidated from 13 parts into one. It is also said to be twice as durable as before. Eight 3D printed cyclonic inducers are fitted to every GE9X engine.
There are plans to re engine around 1,300 Sikorsky UH-60 Black Hawk helicopters and 600 Boeing AH-64 Apache helicopters. Each helicopter has two engines.
Low pressure turbine blades
As previously detailed in TCT Magazine, GE is also having success with the Arcam Electron Beam Melting (EBM) technology. A total of 228 low pressure turbine blades are being additively manufactured on the Arcam EBM A2X in titanium aluminide for each GE9X engine. These components are contributing to an improved fuel efficiency of 10% and are 50% lighter than their traditionally manufactured counterparts. Because of the EBM process raising the temperature inside of the machine to 1,200°C, there are smaller thermal gradients generated and the components experience less residual stress during the build.
One engine - zero tolerance to failure
GE has also thrown 3D printing at its Catalyst engine for the single-engine Cessna Denali aircraft. And it is here where its application of additive gets bigger and more complex.
“We really took a fresh approach to design this engine. This is the next step up,” Philp says.
Additively manufactured advanced turboprop fuel heater for the Catalyst turboprop engine installed on the Cessna Denali
In the additive manufacture of the turboprop engine components, GE has incorporated integrated airfoils into the interiors of engine components to facilitate better performance. The engine is also said to burn up to 20% less fuel and achieve 10% more power than other engines in the same class. Among the parts printed for the Catalyst engine are an advanced turboprop fuel heater, exhaust case and C Sump component.
T700/CT7 midframe
“This is one of the hardest parts still to make, and we’ve been making it for 35 years,” Philp notes of the T700/CT7 midframe.
GE prototyped an additive version of the CT7 midframe, again, focusing on part consolidation. One of the weight-saving opportunities it had recognised was to consolidate parts so that it could remove flanges, nuts, and fasteners in a bid to help save weight, and so it could remove the ‘very complicated’ welding, brazing and assembly of parts. In the development of this prototype, which was subsequently validated on a development engine, GE incorporated 3D printing as much as it could, with the performance ‘exceeding expectations’ of previous iterations of the engine.
Philp suggests the work carried out to additively manufacture larger, more complex components like the CT7 midframe has helped the company to land the T901 contract, within which GE has currently printed and tested additively manufacture components to be used in engine qualification and flight testing.
“We use those lessons learned, that knowledge [from previous projects], to say 'maybe we took it a bit too far, let’s pull it back a little bit.' What you see here are all components for new engines, and that’s really where we see the most bang for our buck in 3D printing,” Philp says. “It’s not just saying I can replace this one part in an engine – that sensor housing was a separate story – when you start to design the engine as a system, with all the benefits of 3D printing, that’s when you gain the performance, weight and fuel savings.”
