The unstable combustion problem in small-sized solid rocket engines with a large aspect ratio is so complicated that its causes remain unclear. In this study, the coupled vibration between the sound field and shell in the engines was proposed as a possible cause. A solid rocket engine structure was abstracted into a multilayer thin-walled cylindrical cavity in this study, followed by the theoretical calculation and simulation calculation of its inherent frequency. Next, a thin-walled cylindrical cavity fluid-solid coupling experimental platform with the function of modal measurement was established to verify the accuracy of simulated modes for the shell structure and acoustic cavity. Then, the mode of the finite element model (FEM) for the solid rocket engine was theoretically calculated and simulated, accompanied by finite element calculation and experiment of the acoustic mode of the internal acoustic cavity. Subsequently, the engine mode was compared with the acoustic mode of the internal acoustic cavity. On this basis, a new cause for the damage and disintegration of the solid rocket engines in the final working stage was revealed. Moreover, a brand-new idea of inhibiting the pressure oscillation-induced unstable combustion in the solid rocket engines was put forward.

中文翻译：

---

大纵横比薄壁圆柱腔动态特性研究

大纵横比的小型固体火箭发动机的不稳定燃烧问题非常复杂，其原因尚不清楚。在这项研究中，发动机声场和外壳之间的耦合振动被认为是可能的原因。本研究将固体火箭发动机结构抽象为多层薄壁圆柱空腔，对其固有频率进行理论计算和仿真计算。接下来，建立了具有模态测量功能的薄壁圆柱腔流固耦合实验平台，验证了壳结构和声腔模拟模态的准确性。然后，对固体火箭发动机的有限元模型（FEM）模式进行了理论计算和模拟，并附有内部声腔声模的有限元计算和实验。随后，将发动机模式与内部声腔的声模式进行比较。在此基础上，揭示了固体火箭发动机在最后工作阶段损坏和解体的新原因。此外，还提出了抑制固体火箭发动机压力振荡引起的不稳定燃烧的全新思路。