Heat Transfer Comparison of Graphite and C/C SiC Inserts in Hybrid Rocket Nozzles Using Coupled Fluid Structure-Simulations

Kurzfassung

Ceramic materials are promising alternatives to graphite for reducing nozzle erosion in hybrid rocket engines. This work presents a thermally coupled fluid-structure interaction study of nozzle assemblies for the AHRES-C engine equipped with two candidate insert materials: graphite and a Ceramic Matrix Composite (CMC) made from Carbon Fibre Reinforced Carbon- Silicon Carbide (C/C-SiC). Two different fibre orientations in the CMC are compared to show effects on the thermal loads. Simulations were performed using the DLR Coupled Numerical Fluid, Flightmechanics and Structure Simulations (CoNF²aS²) environment, coupling the DLR Tau RANS solver with Ansys Mechanical. Results indicate that while the graphite baseline maintains the lowest interface temperatures, C/C-SiC is a viable alternative for short firing durations despite a maximum temperature increase of 80K. Furthermore, fibre orientation influences thermal loads, the configuration of radial and axial fibres demonstrates potential in mitigating local hot spots compared to the radial only configuration. These findings provide essential insights for optimizing the thermal-structural design of erosion-resistant nozzle inserts.