The hybrid rocket motor (HRM) emerges as a promising propulsion system offering thrust adjustment at a low cost. Prior research has indicated that the inclusion of micro Al additives enhances HRM performance, yet a comprehensive investigation remains absent. Thus, this study aims to explore the impact of Al particle additive content and size variation on the characteristics of hybrid rocket motors (HRMs) through experiments and simulations. Firing tests are conducted on HRMs employing unadulterated HTPB, 38 % additive Al (2 μm), and 58 % Al (2 μm). Experimental findings reveal enhancements of 12.6 % and 33.9 % in regression rate, and 2.5 % and 8.0 % in specific impulse for the 38 % Al and 58 % Al fuel configurations, respectively, compared to the base case. Subsequently, a numerical two-phase combustion model is built to analyze the inner flow field characteristics. The high consistency between experimental and simulation results validates the efficacy of the numerical approach employed. Following this, a series of simulations covering Al content ranging from 0 % to 58 % and Al particle sizes from 0.4 μm to 75 μm is conducted. Simulation outcomes indicate that specific impulse and combustion efficiency enhancements correlate with the increase in Al mass fraction for particles with diameters under 35 μm. However, high Al content proves detrimental to specific impulse and combustion efficiency when particle diameter exceeds 35 μm. Additionally, regression rate and thrust demonstrate an increase with Al content, albeit the rate of increment diminishes with larger Al particles. This study comprehensively examines the influence of Al particle addition on HRM performance and elucidates the underlying mechanisms, thereby offering insights into HRM design and manufacture.

中文翻译：

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微细Al颗粒添加剂对HTPB混合火箭发动机性能的数值和实验研究

混合火箭发动机（HRM）作为一种有前途的推进系统而出现，以低成本提供推力调节。先前的研究表明，微量铝添加剂的加入可以增强HRM性能，但仍缺乏全面的研究。因此，本研究旨在通过实验和模拟探讨铝颗粒添加剂含量和尺寸变化对混合火箭发动机（HRM）特性的影响。烧制测试是在采用纯 HTPB、38% 添加剂 Al (2 μm) 和 58% Al (2 μm) 的 HRM 上进行的。实验结果表明，与基本情况相比，38% Al 和 58% Al 燃料配置的回归率分别提高了 12.6% 和 33.9%，比冲分别提高了 2.5% 和 8.0%。随后，建立两相燃烧数值模型来分析内部流场特性。实验和模拟结果之间的高度一致性验证了所采用的数值方法的有效性。随后，进行了一系列涵盖 Al 含量范围从 0% 到 58%、Al 颗粒尺寸从 0.4 μm 到 75 μm 的模拟。模拟结果表明，比冲和燃烧效率的提高与直径小于 35 μm 的颗粒的 Al 质量分数的增加相关。然而，当颗粒直径超过 35 μm 时，高 Al 含量不利于比冲和燃烧效率。此外，回归速率和推力表明随着铝含量的增加而增加，尽管增量速率随着铝颗粒的增大而减小。本研究全面考察了铝颗粒添加对 HRM 性能的影响，并阐明了潜在机制，从而为 HRM 设计和制造提供了见解。