Abstract
*† ‡ Traditional solid fuels used for hybrid rocket propulsion systems have a relatively low massburning rate and density impulse that limits the application to volume limited systems. Two methods were investigated to alleviate this problem: 1) the addition of nano-sized energetic materials to increase burning rate and improve solid-fuel density, and 2) the use of nonpolymeric fuels, which can burn at regression rates many times those of traditional polymeric fuels. Both of these methods were adopted in solid-fuel formulations in this study. The average regression rates attained for a paraffin-based solid fuel formulation containing 13 wt% Silberline ® aluminum particles were 4 times that of the conventional baseline cured HTPB fuels. Instantaneous regression rate data were obtained with the use of X-ray Translucent Casing (XTC) hybrid rocket motor. The deduced instantaneous burning behavior of pure HTPB fuel formulations exhibited very close agreement with the correlation analysis developed by Chiaverini, et al., except that the leading coefficient in the correlation was considered as a function of oxidizer mass flow rate. It was found that the instantaneous values of O/F ratio has a profound effect on radiative-to-convective heat flux ratio and modified blowing parameter, which is more suitable to be used in the evaluation of the Stanton number ratio, St/St0, required for the regression rate correlation. The surface temperature of the metalized HTPB fuel was found to be very close to the melting temperature of Al due to the accumulation of particles on the surface. This accumulation also caused the fuel regression rate to be decreased for a larger port area. The time variation of the instantaneous regression rate of the paraffin fuel was found to depend strongly upon the oxidizer flow conditions and the initial grain geometry.
Published Version
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