Modeling of paraffin-based fuels in the simulation of hybrid rocket flowfields

Simulations of the flowfield in hybrid rockets using paraffin-based fuels are carried out with a Reynolds averaged Navier-Stokes solver. The melted paraffin-wax is treated as a dense fluid because it is in the supercritical pressure regime for typical hybrid rocket conditions. Furthermore, a suitable chemical reaction is added to those describing the combustion process in order to reproduce the cracking mechanism of the melt layer. The gas-surface interaction boundary condition, previously developed and validated for pyrolyzing fuels, is adapted to the case of liquefying fuels in order to compute the regression rate. In addition, the radiative heat transfer contribution is included into the surface energy balance, after being computed via discrete transfer method within the whole thrust chamber. The main results achieved using this modeling approach for paraffin-based fuels are described in detail. Comparison with results obtained with HTPB fuel are also presented.