Scaling Parameters of Swirling Oxidizer Injection in Hybrid Rocket Motors

Hybrid rockets present some disadvantages, mainly low regression rate and combustion inefficiencies. A promising technology to solve both is swirling oxidizer injection, which enhances the wall heat flux and the mixing of the combustion reactants and thus increases the regression rate and the combustion efficiency. A numerical investigation is carried out with a commercial computational fluid dynamics code. This type of analysis can really help with the comprehension of the physical phenomena hidden behind the experimental measurement, and so it can be a powerful aid in the preliminary development and testing of hybrid motors. The first step of this numerical investigation is to study the initial motor geometry, increasing the complexity of the system with the addition of each component one by one to better understand which parameters influence the swirling flowfield inside the combustion chamber. Afterward, a comparison between the axial and swirl injection is done, analyzing the qualitative differences in the flowfields and the quantitative ones in the performance. The central and most important part of this numerical study is focused on the inspection of the motor performance related to several scaling parameters.