Numerical Modeling of Scale Effects in Paraffin-Hydrogen Peroxide Hybrid Rockets with Swirl Injection

A numerical study of scale effects in swirl-injected Hybrid Rocket Engines is performed using axisymmetric Reynolds-averaged Navier-Stokes simulations. The analysis focuses on a lab-scale engine and a scaled-down upper-stage engine demonstrator, both powered by paraffin and hydrogen peroxide. The findings suggest that observed scale effects could be attributed to differences in geometric features, such as the ratio of port to injector diameter. Given the importance of turbulence in swirling flows, emphasis is placed on selecting a suitable turbulence model. Two corrections to the Spalart-Allmaras turbulence model are evaluated to accurately capture the distinctive flow characteristics of the swirling flow, such as toroidal recirculation zones and vortex breakdown phenomena.