Computational Fluid Dynamics Simulation of Hybrid Rockets of Different Scales

CFX software is used to simulate different hybrid rocket configurations, applying liquid N2O as the oxidizer and paraffin as the fuel. This work is the prosecution of a previous paper analyzing liquid injection in a lab-scale hybrid rocket. It is focused on the formulation of the most suitable simulation technique to represent another type of liquid injector, compared with the one described in the previous paper. It also aims at extending the computational fluid dynamics simulation approach to hybrid rockets of larger scales. To validate computational fluid dynamics output, experimental results coming from both a laboratory scale and an increased-scale engine have been used. The different geometries studied include an increased-scale engine with a cylindrical grain having no diaphragm, the same rocket with a one-hole diaphragm inside the fuel grain, and a lab-scale rocket with a one-hole diaphragm. Simulations are steady state, and combustion derives from a single-phase chemical reaction. Liquid injection is fully simulated for the oxidizer, but paraffin entrainment is neglected for the fuel. Computational fluid dynamics results show a good agreement with the corresponding experiments for the ballistic parameters of interest in this study: chamber pressure, efficiency, and C*. Computational fluid dynamics results prove that the simulation technique proposed can be applied to any hybrid rocket scale.