Nov 1, 2016 | By Benedict

General Electric (GE) has tested a demonstrator engine with 35% additive manufactured parts. The engine was made to validate 3D printed parts for the clean-sheet design Advanced Turboprop (ATP) engine, which will power the new Cessna Denali single-engine turboprop aircraft.

The GE CT7 engine, on which the a-CT7 is based

In its quest to turn additive manufacturing into an essential part of the aerospace industry, GE has showcased its most impressive feat of 3D printed engineering to date: an engine comprised of 35% 3D printed parts. The all-new lightweight components for the ATP will contribute to a 5% weight reduction, as well as a 1% improvement in specific fuel consumption (SFC), coming good on the promises made during the initial announcement of the 3D printed engine.

The clean-sheet design ATP will feature metal 3D printed parts which reduce the weight of the engine, not only through topologically optimized structures, but also by requiring fewer connecting parts: “With subtractive manufactured parts and assemblies, you traditionally use bolts, welds or other interfaces to attach the parts together, which adds weight to the engine,” said Gordon Follin, ATP Engineering GM at GE Aviation. “On the ATP, additive reduces weight by eliminating those attaching features while also optimizing design of the parts.”

To validate parts for the ATP, GE developed a CT7-2E1 technology demonstrator engine, the “a-CT7,” which was designed, built, and tested in 18 months. The demonstrator, reverse engineered from an existing (non-additive) CT7 engine, shows the full power of aerospace additive manufacturing, with more than 900 subtractive manufactured parts reduced to just 16 additive manufactured parts. While the demonstrator is not intended to fly, the engine architecture of the ATP is derived from the CT7, allowing for successfully tested additive parts from the a-CT7 to be incorporated into the ATP.

GE's 3D printed fuel nozzle tip

The ATP, which will power the new Cessna Denali single-engine turboprop aircraft, will feature more 3D printed components than any production engine in the history of aviation. 855 subtractive manufactured parts will be reduced to 12 additive parts, with those 12 making up 35% of the total part count. 3D printed parts include sumps, bearing housings, frames, exhaust case, combustor liner, heat exchangers, and stationary flowpath components.

The use of 12 3D printed parts in the ATP engine marks a dramatic increase in additive usage over the CFM LEAP engine, which contained just one instance of 3D printing: a 3D printed fuel nozzle tip. However, the eight engineers who designed the LEAP’s 3D printed fuel nozzle tip returned to the fold to create the 16 additive parts of the demonstrator a-CT7, and further 3D printed parts will be incorporated into the next version of the demonstrator.

According to GE, additive manufacturing has not only helped to reduce the weight of engine parts; it has also helped to increase production speed. The combustor liners, for example, were 3D printed in just two days. “A huge benefit of additive is expedited test schedules,” said Follin. “For a program like ATP, one of our big philosophical points of emphasis is getting hardware to test faster instead of spending too much time with models on a computer. By putting real hardware on test as quickly as we can, we can use the resultant data to help us design the next iteration for a better product, and we get that product much faster than if we were to use conventional manufacturing methods.”

Cessna Denali

The 1,240SHP-rated ATP is the first in a new line of GE turboprop engines aimed at Business and General Aviation aircraft in the 1,000-1,600 SHP range, and should be in the air by the end of 2017. The new Cessna Denali, which will be powered by the ATP, will have a range of 1,600 nautical miles and speeds higher than 285 knots.

GE Aviation Business vice president Brad Mottier recently reported that GE has spent about $1 billion developing its overall additive manufacturing plan. After failing to secure the purchase of SLM Solutions in October, GE eventually purchased 3D printing giant Concept Laser instead.

ATP features:

  • 12 additive parts (35% total part count)
  • 16:1 overall pressure ratio (OPR)
  • 20% lower fuel burn (compared to competitors in same size class)
  • 10% higher cruise power
  • Ruggedized, modular architecture based on CT7 turboshaft
  • All-titanium, 3D aerodynamic compressor for light-weight and efficient power generation
  • Cooled turbine blades enabling higher thrust and fuel efficiency
  • Integrated electronic propulsion control



Posted in 3D Printing Application



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