Failure Mechanism of Combustion Chamber of Liquid Rocket Engine under Severe Multi-Physics Conditions

在液体火箭发动机的研制中，燃烧室的寿命是一个重要的设计问题。然而，由于燃烧室在苛刻的条件下会发生复杂的多物理现象，因此很难定量预测其寿命。日本宇宙航空研究开发机构正在研究LE-X发动机作为下一个助推发动机。在其研发过程中，采用前装式设计方法，力求缩短研制周期、降低成本、提高可靠性。因此，在开发的早期阶段精确评估燃烧室的寿命是必不可少的。为了提高寿命预测的准确性，本文重点研究了热-流行为与结构响应之间的相互作用，提出了一种新的分析方法--高保真多物理场耦合模拟。应用此方法，我们研究了上一级发动机在研制过程中喉道产生残余变形的机理和主要因素。结果表明，喉道的残余变形强烈依赖于停机过程中的冷却能力，而冷却能力受燃气和冷却剂瞬态流动的影响。

In developing liquid rocket engine, life time of combustion chamber is an important design issue. However, it is very difficult to quantitatively predict the life time because complicated multi-physics phenomena occur under severe conditions in the combustion chamber. The LE-X engine is under study in JAXA as the next booster engine. In its research and development, shorter development time, lower cost and higher reliability are sought by using front-loading design approaches. Therefore, it is indispensable to evaluate the life time of the combustion chamber precisely in the early phase of development. In order to improve accuracy in the life prediction, we focus on the interaction between thermo-fluid behaviors and structural responses, and have developed a new analysis procedure, that is, high-fidelity multi-physics coupled simulation. By applying this procedure, we have investigated the mechanisms and the dominant factors of residual deformation occurred in the throat, which was experienced under development of the upper stage engine. It has been revealed that the throat’s residual deformation strongly depends on cooling capability in the shutdown process, which is affected by the transient flows of both combustion gas and coolant.