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Combustion Instabilities Induced by Multi-Stepped Hybrid Rocket Fuel Grains

par De Morais Bertoldi, Artur Elias ;Glaser, Christopher;Hijlkema, Jouke;Lestrade, J.-Y.;Anthoine, Jérôme P.L.R. ;Gelain, Riccardo ;Hendrick, Patrick
Référence Aerospace Europe Conference 2023 – 10ᵀᴴ EUCASS – 9ᵀᴴ CEAS(Lausanne, Switzerland)
Publication Publié, 2023-07-11

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Résumé :

Previous research using Forward Facing Steps (FFS) and Backward Facing Steps (BFS) in the solid fuel grain demonstrated increased regression rates compared to a cylindrical single port. Nonetheless, it is important to assess the combustion instabilities induced by stepped geometries to anticipate (and solve) potential negative side effects. This paper addresses the preliminary experimental results for single and multi-step configurations and their combustion chamber pressure oscillations. Additionally, the impact of a stepped helix approach on the combustion behaviour is assessed. Pressure oscillations in hybrid rockets are not likely to be as limiting compared to their liquid and solid counterparts. However, the instabilities might significantly affect the performance and payload comfort of the propulsive system. In this study, we analyse the interaction between the pressure oscillations in the combustion chamber and the other parameters of the HYCAT (HYbrid with CATalyst) hybrid rocket motor at ONERA. We show that although steps play a major role in pressure oscillations and significantly alter the combustion behaviour of the engine, none of the stepped cases exceeded the most instable no-step test; on the contrary, especially BFSs have the potential to decrease pressure oscillations. This remark is important because multi-stepped grains have significantly higher regression rates (26 % to 245 %) than the cylindrical reference cases.