Research on thermomechanical fatigue life prediction of regenerative cooling thrust chamber

再生冷却推力室热机疲劳寿命预测研究

¹ School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China
² Science and Technology on Liquid Rocket Engines Laboratory, Xi’an 710100, China

Received: 27 October 2021

Abstract

The ratcheting effect of the liner wall structure in the thrust chamber of liquid rocket engine under cyclic load is studied, and its service life is predicted. Firstly, the 3-D heat transfer analysis of the wall of the thrust chamber is carried out while explaining the mechanism of its "dog room" failure. Based on the results of the heat transfer analysis, the stress-strain evolution of the structure under cyclic load is analyzed by nonlinear plane strain finite element method. According to the finite element analysis results, the ratcheting effect of the liner wall structure is described and the ratcheting damage is calculated. The low cycle fatigue damage is calculated by using modified Morrow model, and the creep damage is also calculated using Norton model. Finally, the total damage of thrust chamber liner wall is calculated by using Miner linear cumulative damage law and the thermomechanical fatigue life of the structure is estimated. The result shows that the middle point of the lower surface of the liner wall will fail first, and the calculated service life is 33 times, which is good agreement with its actual service life. In the total damage of the weak point, ratcheting damage, creep damage and low cycle fatigue damage account for 52%, 32% and 16% respectively, indicating that the ratcheting effect is the main reason for the failure of the thrust chamber structure. The research results of this paper provide important engineering reference for the structural optimization design and rapid life prediction of regenerative cooling thrust chamber of liquid rocket engine and the future reusable aerospace power.

摘要

针对液体火箭发动机再生冷却推力室内壁结构多发的"狗窝"失效问题, 仿真再现循环载荷下塑性应变累积的棘轮效应, 并定量分析其对推力室内壁结构寿命的影响。对推力室内壁进行三维传热分析, 在传热分析结果的基础上对该结构在循环载荷下的应力应变演化进行非线性平面应变有限元分析。根据有限元分析结果, 对内壁结构的棘轮效应展开描述并计算棘轮损伤, 分别使用Morrow修正模型、Norton蠕变模型计算其低周疲劳损伤及蠕变损伤。基于Miner线性累积损伤理论, 提出了综合考虑棘轮损伤、低周疲劳损伤及蠕变损伤的推力室内壁结构寿命预估方法。结果表明: 喉部附近内壁下表面中点处会最先失效破坏, 推力室内壁结构使用寿命为33次; 在导致该点的总损伤中, 棘轮损伤、蠕变损伤和低周损伤分别占比52%、32%和16%, 说明了棘轮效应是导致推力室结构失效的主要原因。所提研究方法对液体火箭发动机再生冷却推力室结构的寿命定量分析、优化设计及未来可重复使用火箭发动机设计提供重要的工程参考。