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Making engines eco-friendly: An All-Oxide Inner Turbine Duct for Aero-Engines

09 November 2020

The AllOxITD project goal was to developed an all-oxide Ceramic Matrix Composites (CMC) inter turbine duct for testing in Clean Sky’s “Advanced Geared Engine Configuration (HPC-LPT) demonstrator. Ceramic Matrix Composite materials (CMCs) have excellent properties at high temperatures, as unlike metallic materials they do not lose their strength, withstanding up to 1000°C! 

This behaviour makes CMCs useful for components in the hot gas section of gas turbines. Because the composites can withstand significantly higher temperatures, the need for cooling air can be greatly reduced. Oxide CMCs also have a lower specific weight than metallic materials. Therefore both the lighter weight as well as the reduced need for cooling air have the potential to lower the environmental footprint of an aircraft engine. 

Within the project, CMCs based on filament winding (a fabrication technique that involves winding filaments under tension over a rotating cylindrical rod), woven pre-pregs (reinforced material that has been pre-impregnated with a particular material) and triaxial braids (a way of interlacing materials that makes them stronger) were investigated to determine which would be best to use, taking into consideration their thermomechanical and thermophysical properties at relevant temperatures. 

The woven pre-preg CMC was chosen to be used for the Inter Turbine Duct demonstrator testing and it was further investigated through a verification programme. A quality assurance programme was also worked out for this material. In parallel, the Inter Turbine Duct components were designed by the topic manager, supported by a thermomechanical simulation done by the consortium to generate a CMC-suitable end design. Finally, 25 pre-preg CMC-based Inter Turbine Duct components for demonstrator testing were produced.   
These were important early steps towards potentially bringing European (German) oxide CMC into service in aviation, even though the material quality and dimensional accuracy are not yet fully sufficient. 

Additionally, due to the high level of quality necessary for aviation applications, the development has broad dissemination potential also for other industries. The developed manufacturing processes and Standard Operating Procedures are already used to produce components for non-aviation applications. For example in heat treatment systems for metals and for high-temperature furnaces. The knowledge gained during the project contributed to the designing of a new production line in Heuchelheim, which will become operational in autumn this year. 
The German aerospace centre (DLR), the Institut für Textiltechnik of RWTH Aachen University (RWTH ITA) and Schunk Kohlenstofftechnik GmbH (SKT) made up the consortium of AllOxITD. With a grant of €3.07m, the project ran from December 2015 to May 2020.

Figure: pre-preg CMC ITD parts for testing in demonstrator engine