[论文解读] Performance Analysis of Novel Propellant Oxidizers using Molecular Modelling and Nozzle Flow Simulations

Pujan Biswas, Sudarshan Kumar+1 more|arXiv (Cornell University)|Jan 31, 2022

Rocket and propulsion systems research被引用 1

一句话总结

本研究提出37种新型基于碳的杂环氧化剂，作为固体火箭发动机中高氯酸铵的替代品。采用DFT（B3LYP/6-311++G(d,p)）计算生成热，利用NASA CEA计算理想比冲，结合基于OpenFOAM的超音速喷管流模拟，引入k-epsilon湍流模型与快速畸变理论（RDT）以模拟实际损失，发现实际真空比冲为理想值的88–91%，相较于高氯酸铵最高可提升24秒。

ABSTRACT

Search for alternate fuels for improvement in rocket engine performance is a topic of ever-growing interest and discussion in the research community. The primary target of this paper is to present novel compounds in view of their possible use as oxidizers in propulsion applications using molecular modeling calculations and supersonic flow simulations. Carbon-based heterocyclic compounds tend to have strained molecular structures leading to high heats of formation and energetic behavior. In the present work, molecular modeling calculations for molecules of 37 such potential propellant oxidizers are presented. Density functional theory (B3LYP) was employed for the geometry optimization of the proposed molecular structures using the 6-311++G(d,p) basis set. Heats of formation of the compounds were calculated using the molecular modeling results. Appropriate propellant compositions were considered with the proposed compounds as oxidizer components and Ideal specific impulse (Ivac,ideal*) was calculated for each composition assuming isentropic flow, computed using the NASA CEA software package. To predict the actual delivered specific impulse (Ivac,act*), supersonic nozzle flow simulations of equilibrium product gases of each propellant composition have been carried out using OpenFOAM. The standard k-epsilon turbulence model for compressible flows including rapid distortion theory (RDT) based compression term, has been employed. As the problem is inherently transient in nature, local time stepping (LTS) methodology has been further implemented to reach a steady-state solution. These simulations accounted for divergence losses, turbulence losses and boundary layer losses and gave a more realistic estimation of the specific impulse. It was observed that the Ivac,act* for all propellant compositions lie between 88% to 91% of the corresponding ideal value. The newly proposed oxidizers showed considerable improvement in propulsion performance as compared to ammonium perchlorate which is currently the most widely used oxidizer in solid rocket motors. The maximum improvement observed in Isp was 24 s.

研究动机与目标

• 识别并评估新型基于碳的杂环化合物作为固体火箭推进剂的高性能氧化剂。
• 通过模拟火箭喷管中的非理想流动损失，克服理想化性能预测的局限性。
• 开发一种开源、可访问的方法，利用CFD模拟估算实际输送比冲。
• 将所提出的氧化剂性能与当前固体火箭发动机中使用的标准高氯酸铵进行比较。
• 建立一个通用校正因子（中位数为89.28%），用于将理想比冲转换为实际性能估算值。

提出的方法

• 采用DFT（B3LYP）与6-311++G(d,p)基组进行几何优化与生成热计算。
• 在等熵、无损失假设下，利用NASA CEA软件计算理想比冲（Isp,vac*）。
• 采用OpenFOAM进行超音速喷管流模拟，使用可压缩k-epsilon湍流模型，并引入快速畸变理论（RDT）以模拟压缩过程。
• 应用局部时间推进法（LTS）以在瞬态模拟中获得稳态解。
• 在喷管流中考虑发散损失、边界层损失与湍流损失，以估算实际输送比冲（Isp,act*）。
• 通过网格收敛性与独立性检查验证结果，确保模拟精度。

实验结果

研究问题

• RQ1 在考虑非理想流动损失的情况下，新型氧化剂基推进剂的实际真空比冲是多少？
• RQ2 与理想化预测相比，湍流、边界层与发散损失如何影响固体火箭推进剂的性能？
• RQ3 像OpenFOAM这样的开源CFD框架能否准确预测新型推进剂组成的实际比冲？
• RQ4 在多种氧化剂组成中，实际与理想比冲的中位数比例如何？
• RQ5 能否推导出一个通用校正因子，将理想比冲值转换为新型高能化合物的实际性能估算值？

主要发现

• 所有37种推进剂组成的实际输送比冲（Isp,act*）均在NASA CEA计算的理想值的88%至91%之间。
• 实际性能相对于理想性能的中位效率为89.28%，表明对类似化合物可采用一致的校正因子。
• 相较于高氯酸铵，比冲最高提升24秒，出现在S2-F组成中。
• 不含铝添加剂的推进剂（如S1-2）在减少有毒排放的同时实现了高性能。
• S9-4组成效率最高，达90.19%，实际比冲为231.80秒。
• 本研究证实，湍流、边界层与发散损失显著降低性能，因此有必要采用详细的CFD模拟进行准确评估。