Manufacturing a Ceramic Turbine Rotor for a Compact Jet Engine

Abstract

Compact military-grade jet engines offer many potential applications, including use in remotely piloted vehicles, but can be expensive to use for research and development purposes. A study aimed at increasing the power and thrust output of an inexpensive commercial compact engine found a material limitation issue in the turbomachinery. To gain the additional power, hotter turbine inlet temperatures were required. This temperature increase exceeded the limit of current uncooled metal turbine rotors but could be achieved through turbine rotors made from ceramics, such as silicon nitride, which would allow an increase in the thrust and power output by a factor of 1.44. Current ceramic turbine manufacturing methods are costly and time consuming for rapid prototyping, but recent breakthroughs in ceramic additive manufacturing have allowed for cheaper methods and faster production which are beneficial for use in research and development when designs are being rapidly changed and tested. This research demonstrated, through finite element analysis, that a silicon nitride turbine rotor could meet the increased turbine inlet temperature conditions to provide the desired thrust and power increase. Further, as a proof of concept, an additively manufactured drop-in replacement alumina turbine rotor was produced for the JetCat P400 small-scale engine in a manner that was cost-effective, timely, and potentially scalable for production. This compact engine was used to demonstrate that a cost-effective ceramic turbine could be manufactured. At the time of publication, the desired ceramic material, silicon nitride, was not available for additive manufacturing.

Future directions in ceramic additive manufacturing: Fiber reinforcements and artificial intelligence

“…[195][196][197][198][199] Fine feature resolution (in the range of ∼10-20 μm) is an advantage but limitations in composition (mainly oxides) and/or part thickness (<∼10 mm) are current challenges with commercially available feedstock. 200 Despite these limitations, it remains the most advanced in terms of commercial equipment and ceramic feedstock (3DCeram, Admatec, Lithoz, and Tethon 3D) and ability to make complex shapes (e.g. inner channels) with fine feature size.…”

“…One direction in the field utilizes preceramic polymers to improve the issues with low solids content and/or RI of powders, but is limited to feature sizes (∼<1 mm) due to off‐gassing and shrinkage during the cure and pyrolysis steps, respectively 195–199 . Fine feature resolution (in the range of ∼10–20 μm) is an advantage but limitations in composition (mainly oxides) and/or part thickness (<∼10 mm) are current challenges with commercially available feedstock 200 . Despite these limitations, it remains the most advanced in terms of commercial equipment and ceramic feedstock (3DCeram, Admatec, Lithoz, and Tethon 3D) and ability to make complex shapes (e.g.…”

Delamination mitigation in additively manufactured Al2O3 via enhanced thermal postprocessing

“…A vertical line at 22.6 μm indicates the estimate of critical flaw size (c), which is the maximum allowable flaw size for a given stress, for alumina. 35 It is found using Equation 3, where the K Ic is the fracture toughness, and σ f is the material's modulus of rupture, as reported in ref. 35 .…”

Size effects in 3D‐printed polymer‐derived, zirconium diboride‐reinforced ceramic composites

“…However, even with the greater geometric flexibility that AM affords, porosity and cracking during curing or pyrolysis remain a major obstacle to the creation of bulk ceramic components using preceramic polymers. 5,[8][9][10] The use of filler materials in preceramic polymers can aid in reducing the shrinkage, porosity, and cracking in polymer-derived ceramic composites by providing a rigid framework for the composite during curing and pyrolysis and by providing faster diffusion pathways for the evolved gas species to escape. 2, 12 For example, with a DLP technology, O'Masta et al found that the use of 10 vol.% mullite in a polysiloxane increased the thickness of a part that could be printed without cracking from 1 to <3 mm 8 .…”

“…There is great interest in using preceramic polymers as feedstocks in additive manufacturing (AM) technologies, in part because several AM technologies are already well‐suited to using thermoset resins—in particular stereolithography (SLA), 7 digital light processing (DLP), 8,9 and material extrusion AM 5,10,11 —and in part because ceramic materials are typically challenging to form into complex shapes, a major strength of AM. However, even with the greater geometric flexibility that AM affords, porosity and cracking during curing or pyrolysis remain a major obstacle to the creation of bulk ceramic components using preceramic polymers 5,8–10 …”