Based in Florida, KW Micro Power is a small manufacturer of high powder density Auxiliary Power Units (APU) for commercial aviation and military applications. It teamed up with the engineers at nTopology and VELO3D to develop a generator housing for an airborne microturbine that is 44% lighter and printed as a single component with conformal cooling channels.
The housing initially weighed 10.4kg and was made up of multiple CNC machined parts that were later assembled. KW Micro Power was concerned not only with the weight of the airborne component, but also that the alignment of the parts upon assembly could hinder the housing’s reliability when the engine was spinning at up to 90,000 rpm.
Using nTopology’s nTop platform, the partners tackled these issues by first using the software’s integrated static and modal analysis simulation tools to confirm the loads of the housing were relatively small, and then removing unnecessary material to create a hollow shell with a variable wall thickness. The removing of material from the design model is said to have taken 100 milliseconds, while also allowing the engineers to improve the thermal management of the housing by converting the empty shell into conformal cooling channels.
Harnessing FE analysis and simulation tools within nTop and carrying out CFD simulations via Ansys Fluent, the effect of the cooling channels on the housing’s performance was analysed. The results showed that the maximum operating temperature was reduced by 33%, allowing aluminium to be used for the printing of the part, and the external temperature dropped by 86% to 27°C, making it safe to touch. KW Micro Power also decided it would use fuel as the heat transfer medium to cool the engine and preheat the fuel itself, enhancing the efficiency of the combustion process. The company expects the new design to significantly extend the machine life of the generator and says the redesign with nTopology’s nTop platform took just one day.
“Nothing is fast enough for me, but everything is instantaneous in nTopology. I can do the things that I want to do that are impossible with other design tools,” commented Enrique Enriquez, President of KW Micro Power. “I think this is like the renaissance of engineering. In the past, we were always working from the outside. Now, we can control every aspect of the geometry of our designs and their microstructure. If you want to make jet engines and APUs lighter and more efficient, this is the way.”
Having made the effort to smooth the internal geometry to ensure no support structures were required during the additive manufacturing process, as well as enabling aluminium as a material option, KW Motor Power decided to proceed with VELO3D’s metal 3D printing process. Harnessing the Sapphire metal 3D printer and Aluminium F357 material, the microturbine housing was printed in a single piece. Having moved through the redesign of the housing so quickly, KW Motor Power may be able to launch the new microturbine this year, but is still working with the partners to add further advancements. Since the redesigned housing was printed, the companies have been exploring the potential for lattice structures to be integrated. This would help reduce the weight even further and also make room for electronic sensors and filters to be embedded, allowing the generator to be monitored in real-time.
“This component is a testament to what can be achieved by aggressive engineering companies that leverage next-generation design and manufacturing tools,” offered Zachary Murphree, VP of Sales at VELO3D. “KW Micro Power was able to use the unique capabilities of nTopology to design a part that is specifically optimised for the application and using VELO3D’s manufacturing technology meant that there were no compromises for manufacturability.”
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