New CMC turbine vanes successfully tested in wind tunnel

The 3DCeraTurb project research team — comprising multiple institutes within the German Aerospace Center (DLR, Cologne) — is exploring how ceramic matrix composites (CMC) can be used to manufacture high-pressure turbine vanes for aeroengines. The goal is to reduce weight as well as the need for cooling air/expensive coolant, resulting in reduced emissions toward achieving net-zero aviation. These new CMC inlet guide vanes were developed, manufactured, coated with environmental barrier coating (EBC) and tested by an interdisciplinary team.

Three SiC/SiC turbine vanes were recently manufactured at the DLR Institute of Structures and Design department of Ceramic Composites and Structures. During the 3DCeraTurb project, DLR’s liquid silicon infiltration (LSI) manufacturing process was adapted from flat plates to a more complex geometry for the first time. A particular challenge was the draping of dry fabric layers into a graphite mold to apply a chemical vapor infiltration (CVI) fiber coating. Another highlight was the demonstration that cylindrical cooling holes could be integrated into the trailing edge of the CMC vanes without damaging the material.

Wind tunnel tests were then performed at the DLR Institute of Propulsion Technology in Göttingen. The new heat-resistant inlet guide vanes, made of SiC/SiC CMC, are aimed for a geared turbofan engine. The lower density of fiber-reinforced ceramics makes it possible to reduce the weight of these components, and thus the overall engine, resulting in an improved thrust-to-weight ratio. Also, due to CMC’s high-temperature resistance, no coolant is required, yet the turbine vanes can withstand up to 1315°C.

3DCeraTurb project

DLR’s 3DCeraTurb project (2021-2024) focuses on the design and manufacture of a turbine vane using SiC/SiC CMC with the goal to establish a process chain for CMC component design, fabrication, EBC coating, wind tunnel validation and damage assessment.

Inlet guide vane for high-pressure turbine. A new turbine profile was designed based on the engine-side boundary conditions of the existing UHBR-GTF engine preliminary design from the DLR Perfect project. The complex vane geometry is a major challenge for the manufacturing process. The up-scaling of CMC manufacturing know-how from flat specimens to a 3D component is key to improving the usability of these materials which offer higher temperature resistance in the hot gas path.

Improved CMC lifetime prediction. Manufacturing process information and data will be integrated into a multiscale simulation to account for manufacturing influences and improve the overall modeling and life prediction of CMC parts. In addition to the material’s microstructure, lifetime limiting damage initiation and damage evolution can also be taken into account consistently over the entire operation period using a phase field approach. Traceability and consistency of the data generated by the project will be ensured by a provenance data system, which is the first component of an automated process chain covering various aspects and details of aerodynamics, structural mechanics and manufacturability.

Wind tunnel testing. In order to analyze and evaluate the aerodynamic performance, these CMC vanes have been tested in the straight cascade wind tunnel at the DLR Institute of Propulsion Technology in Göttingen at TRL 4.