Numerical simulations of fuel shape change in paraffin-oxygen hybrid rocket engines

Reynolds–averaged Navier–Stokes (RANS) simulations with sub-models of turbulence, chemistry, fluid-surface interaction, and radiation of the internal ballistics of a 1000 N paraffin-oxygen breadboard are performed in this work. Firstly, the effects of the pre-chamber and post-chamber cavities at the initial, average, and final diameter of a reference burn are assessed to be negligible. Then, numerical simulations modeling the fuel shape change in space and time are compared to simulations performed at uniform port radius. The latter provide reasonable regression rate, pressure, and final grain profile predictions with reduced computational cost. On the other hand, the more computationally expensive fuel shape change simulations raise the model prediction capabilities and ensure a more accurate comparison with experimental data. The fuel shape change approach is finally applied with success to simulations of a throttled burn.