Abstract: In order to predict the structural dynamic characteristics of a staged combustion liquid rocket engine，a new synthetic technology for substructure test model was adopted for structural dynamic analysis of the four parallel connected liquid rocket engines. By considering the material differences between the inner and outer wall of the nozzle，the precise finite element model of the nozzle was established using the principles of mass and stiffness equivalence. Then the finite element model of the rocket engine was established using the method of distributed parameters. The results show that the error of the substructure model of the single engine model is less than 1.35%. The error of the model of four parallel connected engines is less than 2.19%. And the simulation modes of vibration are very consistent with the ones obtained from the practical test modal values. It shows that the calculation results by this method are reliable. And it can improve the precision and efficiency of structural dynamic analysis.

Key words: Liquid propellant rocket engine；Substructure test model；Test modal analysis；Modal parameters；Finite element method

摘要： 为了预测补燃循环液体火箭发动机的结构动态特性，采用子结构试验建模综合技术，对四机并联液体火箭发动机的结构动力学进行了研究。在考虑喷管内外壁材料差异的基础上，利用刚度和质量等效原则，建立了精确的喷管有限元模型，然后采用分布参数法建立了发动机有限元模型。结果表明:单机子结构模型的误差小于1.35%；四机并联发动机模型的误差小于2.19%；且仿真振型与实际模态试验结果保持一致。说明该方法的计算结果可靠，能提高结构动态分析的精度和效率。

关键词: 液体推进剂火箭发动机；子结构试验建模；试验模态分析；模态参数；有限元法