In this study, the effects of fuel port geometry and fuel additives on the performance characteristics of additively manufactured solid fuels in a hybrid rocket are explored. Static rocket motor firings were used to examine the performance characteristics, such as fuel regression rate and $C^{*}$ efficiency. Using a baseline fuel of poly(methyl methacrylate) (PMMA), a traditional center-perforated fuel grain as well as elliptical and swirl-elliptical port geometries were considered. The effect of aluminum as a solid fuel additive to the center-perforated fuel grain and the swirl-ellipse geometry was also investigated. Custom 3-D printer filament was developed, enabling the manufacture of fuels containing 10 and 25 wt % nano-aluminum as well as 25 wt % micron-sized aluminum allowing for a direct comparison of aluminum particle concentration and size. The swirl-ellipse geometry alone improved regression rates by about 35%, while exhibiting similar $C^{*}$ efficiency as the center-perforated fuel grain. The combination of the addition of nano-aluminum and the swirl-ellipse geometry resulted in an overall regression rate increase of about $2.5\times$ compared to the baseline PMMA center-perforated grain geometry.

在这项研究中，探索了燃料端口几何形状和燃料添加剂对混合火箭中添加剂制造的固体燃料的性能特性的影响。静态火箭发动机点火用于检查性能特征，例如燃料回归率和$C^{*}$效率。考虑使用聚甲基丙烯酸甲酯（PMMA）的基准燃料，考虑了传统的中心穿孔燃料颗粒以及椭圆形和涡旋椭圆形的端口几何形状。还研究了铝作为固体燃料添加剂对中心穿孔燃料颗粒和旋流椭圆几何形状的影响。开发了定制的3-D打印机灯丝，从而能够制造包含10和25 wt％的纳米铝以及25 wt％的微米级铝的燃料，从而可以直接比较铝颗粒的浓度和大小。仅涡旋椭圆几何形状就将回归率提高了约35％，同时表现出相似的$C^{*}$效率为中心穿孔的燃料颗粒。纳米铝的添加和涡旋椭圆的几何形状相结合导致整体回归速率提高约$2.5\times$ 与基线PMMA中心穿孔的晶粒几何形状相比。