Session: 02-02 Design and Application of CMC Materials and Components

Paper Number: 126286

126286 - Design and Manufacture of EBC Coated SiC/SiC Nozzle Guide Vanes for High-Pressure Turbines 

Increasing the efficiency of jet engines is essential for more environmentally friendly air transport. Higher temperature resistance and lower weight of the combustor and turbine components are key requirements for new materials. Along with adapted environmental coating systems and cooling features, ceramic matrix composites (CMC) are strong candidates for aircraft applications. They can withstand high temperatures in an aggressive environment, while their density is two-thirds lower than that of conventional nickel-based alloys, leading to savings in cooling air and improvements in engine efficiency.

As part of the DLR project “3DCeraTurb”, turbine vanes made of silicon carbide fibre-reinforced silicon carbide composites (SiC/SiC CMC) are developed. One aim of 3DCeraTurb is to design and manufacture ceramic nozzle guide vanes (NGV) for a high-pressure turbine (1^st stage), experimentally investigate the vane behaviour in a wind tunnel, and evaluate performance, damage and lifetime for later application in an aircraft engine. The focus is the enhancement of the manufacturing process from plate dimensions to more complex three-dimensional components. A ceramic-based design serves as a basis for the development and manufacture of a new NGV geometry, considering material- and manufacturing-specific constraints.

The liquid silicon infiltration (LSI) process was used to manufacture the SiC/SiC vanes. The process begins with the draping and CVI fibre coating of woven fabrics. During this stage, shaping occurs, and the final component contour is defined. The fibre preform was then infiltrated with a phenolic resin, which acts as a carbon source, using resin transfer moulding, followed by high-temperature pyrolysis. The resulting porous carbon matrix was infiltrated with a silicon-boron melt, leading to the conversion of the carbon into a SiSiC matrix. To meet the high requirements for surface roughness and geometric and positional tolerances, the surface was ground. Cylindrical, laser-drilled cooling holes were introduced for cooling the trailing edge. In the final step, an environmental barrier coating system (EBC) consisting of yttrium disilicate and yttrium monosilicate layers was applied using PVD processing.

To assess whether the vane can withstand the occurring loads, a strength analysis was performed through structural simulations. Therefore, computational fluid dynamics (CFD) simulations were coupled with a finite element analysis (FEA). Steady Reynolds-averaged Navier-Stokes (RANS) simulations have been performed with the CFD solver TRACE at the highest loads: Take-off End of field (TO EOF). Compared to this scenario, the mechanical and, especially, the thermal loads occurring during wind tunnel testing under TRL 4 will be comparable small, so it is expected that no damage will occur during wind tunnel tests.

For the CFD-FEA coupling, the heat transfer coefficient, temperature and pressure at the boundary layer of the hot gas flow were used as load inputs for the finite element model. The model was built based on the SiC/SiC vane geometry, including the EBC coatings. Ansys was used with the included Ansys Composite PrepPost (ACP) tool to represent the characteristic, direction-dependent properties of CMC. In the first step, a thermal simulation was used to calculate the component’s temperature based on the heat transfer coefficient equilibrium. In the second step, this temperature was used in combination with the surface pressure to calculate the thermo-mechanical stresses. Finally, the safety factors are calculated using the Tsai-Wu criterion.

Presenting Author: Fabia Süß German Aerospace Center (DLR), Institute of Structures and Design

Presenting Author Biography: Short CV: Fabia Süß
- Master of Science in Material Science and Engineering at the Karlsruhe Institute of Technology (KIT)
- Employed since November 2018 at the German Aerospace Center (DLR) in Stuttgart as a research associate
- Works at the Institute of Structures and Design in the Department of Ceramic Composites and Structures
- Responsible for material and component development in the field of SiC/SiC composite ceramics
- Supervises third-party and DLR internal projects related to SiC/SiC development

Authors:

Fabia Süß German Aerospace Center (DLR), Institute of Structures and Design
Robin Schöffler German Aerospace Center (DLR), Institute of Propulsion Technology
Lion Friedrich German Aerospace Center (DLR), Institute of Structures and Design
Anna Petersen German Aerospace Center (DLR), Institute of Propulsion Technology
Felix Vogel German Aerospace Center (DLR), Institute of Structures and Design
Martin Frieß German Aerospace Center (DLR), Institute of Structures and Design
Andrea Ebach-Stahl German Aerospace Center (DLR), Institute of Materials Research