Ballistic and mechanical characteristics of paraffin-based solid fuels

摘要

In a hybrid rocket, paraffin-based fuels are characterised by high regression rates and zero chemical explosion potential. However, paraffin wax is a brittle material and exhibits poor mechanical strength. The production of large-scale paraffin motors is a challenging task because of the poor structural performance of such motors. The addition of polymers and metallic additives to paraffin wax can considerably enhance mechanical performance. In this study, three different paraffin-based fuels, namely paraffin-aluminium (P-Al), paraffin-boron (P-B), and paraffin-carbon black (P-CB), were prepared using polyethylene (PE) polymer additive. The effects of these additives on the thermal, mechanical, and ballistic performance of the paraffin-based fuels were examined. The mechanical strength of these fuels was evaluated using compressive tests. Differential scanning calorimetry (DSC) experiments were performed to study the thermal decomposition of these paraffinbased fuels. A lab-scale ballistic evaluation motor was used to study the regression rates in a gaseous oxygen environment. The results revealed that the addition of the polymer and metallic additives improved the mechanical strength of fuels. The DSC results demonstrated that the addition of the additives accelerated oxidation and improved the heat release rate during combustion. The oxidation enthalpies for the P-Al, P-B, and P-CB samples were 291, 274, and 268 J/g, respectively. Finally, the ballistic results indicated that the regression rate decreased when 10 wt% PE was added to the paraffin wax, and such depreciation of regression rate due to polymer addition was compensated by the addition of the Al, B, and CB additives.