大推力液体火箭发动机启动冲击响应特性研究

摘要

The adaptability of large thrust liquid rocket engine ( LRE ) to start-up impact environment has great influences on the reliability and safety of engine as well as rocket. Refined, systemic 3-D dynamics modeling tech⁃niques are developed for large thrust LRE. The component and whole models of engine are established, the numeri⁃cal model is modified using the element-type model updating method in combine with the modal test data, so that dynamics model of engine structure can be accurately built up. Based on the theory of shock dynamics, the analyti⁃cal method of nonlinear transient dynamics was proposed, which is applied to investigate the effects of start-up im⁃pact dynamics environment on the engine. The dynamic response of the engine structure under transient, strong shock excitation has also been studied in this paper. The results show that the predicted first four modes are in good agreement with experimental data, suggesting that the accuracy of the model can meet the requirement of impact dy⁃namics analysis. The validity of the current analytical method is examined by comparing the calculated response data with experimental results at the vibration monitoring point. It is shown that the proposed analytical method performs well and also indicated that the dynamic displacement can meet the demand of structural interference and motion envelope. Otherwise, the weakest joint strength of the engine structure is located at the supporting plate of oxidant inlet pipeline, which can be improved by changing the shock resistance design of the structure. The modeling tech⁃nique and impact dynamics analytical method of this research provide a technical approach for accurately predicting and testing the dynamics characteristics of the large thrust LRE.%大推力液体火箭发动机结构对启动冲击环境的适应性对于发动机自身及火箭的可靠性与安全性均有重大影响。提出了精细化、系统性的发动机三维动力学建模技术，建立了组／部件及整机模型，采用元素型模型修正方法和模态测试数据对数学模型进行修正，获得准确的发动机结构动力学模型；基于冲击动力学理论，提出了研究发动机启动冲击力学环境效应的非线性瞬态动力学分析方法，仿真研究了结构对瞬态、强载荷冲击激励的动力响应规律。研究结果表明，预示前四阶模态与试验结果的一致性较好，模型的准确性满足冲击动力学分析要求；振动监测点的响应预测数据与试验测量值基本吻合，验证了启动冲击作用下结构瞬变过程分析方法的有效性；发动机的动态位移满足结构总体干涉和运动包络要求，掌握了发动机结构的薄弱环节在发动机氧化剂入口管的固定支板处，通过抗冲击结构改进设计成功地解决了该问题，提高了发动机结构的抗冲击能力和可靠性；文中的建模技术及冲击动力学分析方法为发动机结构精准动力学预示及试验提供了技术途径。