Abstract: Traditional dynamics analysis methods show their limitations in effective dealing with dynamics problems of large complex engineering structures. To improve this， a new multilevel dynamic substructure method is proposed. After a brief presentation of the fundamental ideas of multilevel dynamic substructure method， then the engineering realization method of using multilevel dynamic substructure technology to dynamics modeling and analysis is explained in detail. This new approach is then applied to study the structural dynamic characteristics of a large four parallel connected liquid rocket engines. The results show that the first six modes of simulation are maintained in accordance with modal test values， the modal frequency relative errors are less than 5%， and the modal assurance criterions (MAC) are larger than 0.9. In further， the dynamics analysis method can predict dynamic characteristics of the engine accurately. In comparison with the complete finite element analysis method and traditional (single-level) substructure method， the modeling and solving efficiency have been improved significantly. The multilevel dynamic substructure method has been proven to be a reliable and effective tool in investigating of the large complex structural dynamics.

Key words: Multilevel dynamic substructure；Structural dynamics；Modeling analysis；Liquid rocket engine

摘要： 针对传统动力学分析方法无法有效地解决大型复杂工程结构动力问题的局限性，引入了一套适用于复杂大系统结构建模分析的新技术—多重动态子结构法。详细论述了多重多级动态子结构基础理论，介绍了采用多重动态子结构技术进行动力建模分析的工程实现方法，并开展了该方法在某大型四机并联液体火箭发动机中的应用研究。研究结果表明:仿真分析的前六阶模态与试验值吻合较好，模态频率的相对误差小于5%，模态置信因子MAC≥0.9，该动力分析方法可准确预示发动机结构的动力学特性；相比整体有限元分析方法及传统(单级)子结构法，其建模、求解效率得到大幅度提高；验证了多重动态子结构法是研究大型复杂结构动力问题的一种有效方法。

关键词: 多重动态子结构；结构动力学；建模分析；液体火箭发动机