Modeling and simulation of paraffin–based hybrid rocket internal ballistics

The use of paraffin–wax appears very promising to allow high regression rate single–port fuel grains and a full exploitation of hybrid rockets in space applications. Although the technology development of paraffin–based hybrid rockets cannot leave out experiments, the relevant computational fluid dynamics modeling is crucial to study the coupling of different physical/chemical phenomena occurring in the thrust chamber. In particular, internal ballistics predictive capabilities are needed to effectively use computational fluid dynamics simulations for design optimization purposes. In the present paper a comprehensive model able to predict the internal ballistics of paraffin–based hybrid rockets is presented. The proposed single–phase model takes advantage of typical supercritical pressure conditions of melted paraffin–wax, when injected into hybrid rocket ports. Validation of the approach is carried out by rebuilding selected firing tests of a medium–scale gaseous–oxygen/paraffin–wax hybrid rocket engine available in the literature. The comparison of numerical results against experimental data is finally carried out in different conditions showing encouraging results.