CAREER: Control of Additively Manufactured Solid Rocket Fuel Grain Geometries and Combustion Analysis

高能材料，如炸药、燃料、烟火药剂或推进剂，具有相对较大的储存量。高能推进剂经历的能量转换过程，加上气体排放，导致了一种高效的车辆推进方法。这通常是通过点燃推进剂来实现的，推进剂被构造为颗粒，使其燃烧并排出气体，例如在动力飞行期间从火箭中排出的气体。目前，人们对高能材料添加剂制造或3D打印的理解有限，即三维部件是由以浆料或浆料形式沉积的多层材料构成的。当前的粮食制造工艺受到含能材料在粮食形成过程中的厚性和耐浇注性的限制。这项由学院早期职业发展(CALEAR)奖支持的研究旨在建立关于添加剂制造工艺、材料参数和零件几何形状对印刷性和燃烧效率的影响的基础知识。这项工作涵盖了几个学科，包括燃烧、流体动力学、计算科学、材料科学、控制和推进。这项研究的结果直接与航空航天和国防工业有关，并为汽车、化工、能源和医疗保健部门使用的类似材料和工艺带来了额外的好处。该项目还融入了工程教育部分，包括向中学生推广，并将研究成果整合到本科课程中。添加制造提供了一种方法，可以创建复杂的颗粒几何形状，这是当前传统制造方法所不可能的，通常涉及铸造过程。通过添加制造来生产推进剂具有多项优势，包括能够制造螺旋孔、具有内部尺寸和形状变化的中心穿孔、不同材料和嵌入部件。随之而来的是性能的改进，如燃烧效率的提高、退化率的提高和更好的可控性。这些含能材料添加剂制造的限制因素是优化性能和制造的控制参数方面的知识差距，例如浆料或粘结剂转移的粘性参数、层间结合、层/表面粗糙度、材料转移过程中的沉淀、层组成、分辨率和空洞缺陷。该奖项支持开发制造过程的数学模型、谷物性能模拟、制造谷物的实验设备以及人造谷物的测试。这项工作将测试一种假设，即可以通过制定参数公式-浆料或粘结剂转移的粘度、层/表面粗糙度、分辨率和沉淀物-来获得使用添加剂制造的发动机的最佳推进剂效率。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Energetic materials such as explosives, fuels, pyrotechnic compositions, or propellants have a relatively large amount of stored chemical energy. The energy conversion processes that energetic propellants undergo, coupled with gas expulsion, lead to a highly efficient method for vehicle propulsion. This is typically achieved by igniting the propellant, which is constructed in segments called grains, causing it to burn and expel gasses, such as those expelled from a rocket during powered flight. Presently, there is limited understanding of energetic material additive manufacturing, or 3D printing, when a three-dimensional part is constructed from multiple layers of material deposited as a slurry or paste. The current grain manufacturing processes are limited by the thick nature and resistance to pouring of the energetic materials during grain formation. The research supported by this Faculty Early Career Development (CAREER) award aims at building fundamental knowledge about the effects of the additive manufacturing process, material parameters, and part geometry on printability and combustion efficiency. The work encompasses several disciplines including combustion, fluid dynamics, computational sciences, material science, controls, and propulsion. The outcomes from this research directly relate to the aerospace, aeronautic, and defense industries with additional benefits for similar materials and processes used in the automotive, chemical, energy, and healthcare sectors. The project also incorporates an engineering education component involving outreach to middle school students and integration of research outcomes into undergraduate coursework.Additive manufacturing provides a means to create complex grain geometries not possible with current conventional manufacturing methods, which typically involve a casting process. Producing propellants through additive manufacturing offers several advantages including the ability to create helical ports, center perforations with internal size and shape variations, different materials, and embedded components. With these advantages come performance improvements such as increased combustion efficiency, improved regression rates, and better controllability. The limiting factors for additive manufacturing of these energetic materials are knowledge gaps in governing parameters for optimal performance and manufacture such as viscous parameters for slurry or binder transfer, interlayer bonding, layer/surface roughness, sedimentation during material transfer, layer composition, resolution, and void defects. This award supports the development of mathematical models for the manufacturing process, grain performance simulations, the experimental apparatus to manufacture grains, and the testing of manufactured grains. This work will test the hypothesis that a formulation of parameters – viscosity for slurry or binder transfer, layer/surface roughness, resolution, and sedimentation – can be achieved to obtain optimized propellant efficiency of motors constructed using additive manufacturing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.