Development of CMC Combustion Chambers for Advanced Propellants in Space Propulsion
Creators: name:  B. HEIDENREICH 
name:   L. DAUTH 
name:   R. JEMMALI 
name:   F. SUsz 
name:   M. FRIEsz 
name:   H. ELSAszER 
name:   M. KURILOV 
name:   L. WERLING 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: PROPULSION PHYSICS
FUTURE FUELS

description: In the frame of the DLR interdisciplinary project \"Future Fuels\" the DLR Institutes of Space Propulsion, Combustion Technology and Structures and Design are developing different green propellant systems for the use in rocket engines in the sub-project Advanced Rocket Propellants (TP5). Besides the propellants itself, also combustion chamber structures made of a variety of light-weight and high temperature stable ceramic matrix composites (CMC) are in the focus. These so-called C/C-SiC and SiC/SiCN materials are based on carbon or silicon carbide fibers, embedded in carbon and silicon carbide (C/C-SiC) or silicon carbon nitride (SiC/SiCN) matrices. C/C-SiC materials have been developed at DLR since the late 1980s and are manufactured via the liquid silicon infiltration (LSI) process. The LSI process is based on three process steps. In the first step, carbon fibre reinforced polymer (CFRP) preforms are manufactured in near net shape technique. For the tubular combustion chambers, CFRP tubes with an inner diameter of 36 mm have been made based on three different carbon fibre types (high tenacity (HT), intermediate modulus (IM) and ultra-high modulus (UHM)) and two different manufacturing methods. HT fibre based CFRP tubes were made via the so-called prepreg wrapping method, using 2D carbon fibre fabric, pre-impregnated with phenolic resin, as well as via wet filament winding technique. For IM and UHM fibre-based tubes, wet filament winding with a phenolic resin precursor was used, only. In the second process step, the CFRP tubes were pyrolyzed at a maximum temperature of 1650 C in nitrogen atmosphere, leading to carbon fibre reinforced carbon (C/C) preforms. In the third and last process step, the C/C preforms were siliconized at 1650 C in vacuum. Thereby, molten Si was infiltrated in the porous C/C by capillary forces and the SiC matrix was built up by a chemical reaction of Si and C, leading to dense C/C-SiC tubes. Since C-fibres are prone to oxidation at temperatures exceeding 450C and water vapour degradation beyond 800C and are thus limited to short term applications at high temperatures, a new approach with higher oxidation and corrosion resistant SiC-fibres was considered. Therefore, SiC-fibres were filament wound on a mandrel and infiltrated with a Si-based preceramic polymer (polysilazane) via resin transfer moulding (RTM). After curing and pyrolysis, the porous SiC/SiCN tube was densified by repeated cycles of precursor infiltration and pyrolysis. (PIP-method), leading to fairly dense SiC/SiCN tubes. The mechanical properties of the CMC tubes were determined by internal pressure tests, using an adapted test set-up for hydraulic testing at room temperature. Material composition was investigated on samples in the scanning electron microscope. The tube quality was controlled by process-accompanying inspections as well as by computer tomography. In this presentation, the manufacture of the different CMC tubes and liners is described in detail. Test results are shown and correlated to the fiber types and manufacturing methods. Furthermore, a new concept and manufacturing method for a cooled combustion chamber, based on a sandwich structure, will be presented.