Staying Cool: How Metal 3D Printing Enabled the Intricate Design of This Helicopter Heat Exchanger


What do the wings of a butterfly, the feathers of a bird, the retinal cone cells of a tree shrew and this helicopter heat exchanger have in common?

It is the use of gyroid structures to facilitate flight, sight and, in the case of the aluminum component printed on a EOS Machine M 290, the optimal cooling of a helicopter gearbox. At least that’s the hope of Andreas Vlahinos, CTO of Advanced Engineering Solutionswho currently sees his TCT Award Winner the design goes through a qualification process for use on commercial helicopters.

Gyroids have a periodic triple morphology with no planes of symmetry, no built-in straight lines, and are well suited for parts that need strength without too much weight. The heat exchanger developed by Vlahinos has an internal volume filled with gyroid structures that promote uniform cross-flow throughout the part to cool the gearbox. The use of lattice screens at the end of the inner gyroid domain has also helped eliminate the need for support structures inside the component, while the outer lattice ribs minimize the shell thickness requirement .

With the entry of these design features, the heat exchanger is expected to perform 4 times better than the original design, is approximately half the size, and has improved fatigue life since it is made in a single component as opposed to several parts brazed together.

“The traditional design of these heat exchangers, they call it shell and tube and there’s a bunch of components brazed together,” Vlahinos told TCT. “Soldering thin components is not good for fatigue resistance because there is a lot of vibration in the helicopter, so you have to keep monitoring the fatigue resistance of the heat exchanger and that’s dangerous because the fuel goes through it and you don’t want them to mix it up. This one is very sturdy because there are no welded parts. In testing the design was 300 PSI and we went to 5000 PSI to break it, so there’s plenty of headroom.

In the design and development of this heat exchanger, Vlahinos was responsible for much of the first 80% of the work. For the last 20%, he contacted the Additive Spirits consulting branch of EOS, integrating Maryna Ienina, AM Academy – Product and Partnership Manager, and David Krzeminski, Additive Minds Consultant, into the fold. From the start, Vlahinos used PTC CREO’s lattice generation tools to create the gyroid structure inside and the lattice structure outside, with the thickness of the gyroid increased at the entrance and exit. cold to prevent hot fluid from entering these channels. When integrating Additive Minds, a digital twin of the process was implemented to run simulations that would assess the performance of the design and manufacturing process, with EOS going slice by slice to identify potential hotspots.

“By creating this digital factory, there are ways to understand if the parts will be of high quality, and there is also a place to monitor the condition of the machine to perform predictive analyzes of the condition of the machine and to understand if the machine lived up to the qualifying specification,” Ienina said.

With the help of this digital twin, the part was successfully printed the first time. A demo piece that had been scaled down was later displayed at A CUP and was presented to FAST + TCT show in Detroit delivered by Vlahinos, who says the design wouldn’t be possible without the tools he had.

“The bottom line is that this kind of geometric complexity cannot be made with traditional manufacturing methods,” he said, before also adding, “It will be impossible to design something like this without the tools of simulation, because tribal knowledge and intuition is not enough for these complex geometries. Thus, simulation was necessary because we do trial and error in simulation instead of building and testing. We went through at least a dozen iterations in the simulation.

In terms of printing, the decision was made to continue with the EOS M290 machine, partly because two units of the component could be additively manufactured at once, but also because Additive Minds wanted to demonstrate the ability to print a part with such complexity. structures on a not “too sophisticated” machine. Vlahinos thinks the printed part could be revolutionary, and with the ever-increasing application of heat exchanger additives, EOS also thinks it could have a huge impact in aviation.

“Basically, almost every square inch or element has to be purposely designed for its intent – ​​you’ve heard of purposely designed? I think it demonstrates that,” Krzeminski said. “You can use every inch towards the end use, it’s not, ‘well, we have to have this feature here because of this manufacturing process, but it’s kind of a waste, or get more material here because it’s brazed or welded’, you can squeeze every drop, if you want, of this application into this space.

This article originally appeared in TCT Magazine Europe Volume 30.3 and TCT Magazine North America Volume 8.3.

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