液氧/甲烷发动机推力室多循环热-结构分析

Multi-Cycle Thermo-Structural Analysis of Thrust Chamber for Liquid Oxygen/Methane Engine

关键词:  甲烷  液体火箭发动机  再生冷却  推力室  热分析  结构分析  有限元法

Key words:  Methane  Liquid rocket engine  Regenerative cooling  Thrust chamber  Thermal analysis  Structural analysis  Finite element method

摘要:

为了研究一款液氧/甲烷发动机推力室多循环工作状态下的结构变形，拓展并验证了一种包括流动-传热分析和非线性有限元分析的热-结构分析方法。通过该方法得到了推力室热载荷与压力载荷分布，并分析了推力室在这些载荷下的应力应变响应。研究表明：推力室整体结构变形并非主要取决于热载荷，压力载荷引起的冷却通道底面弯曲在喷管扩张段尤其明显；后冷阶段产生的弹塑性拉伸应变大于热试阶段产生的压缩应变是导致每次循环结束后结构产生残余应变的直接原因；随着工作循环次数的增加，扩张段的冷却通道底角位置残余应变累积速率最快，该部位被确定为结构失效的潜在位置；增加冷却剂入口附近的通道底面厚度、减小后冷阶段与热试阶段的温差以及将冷却通道的尖锐底角设计为圆角可以成为抑制变形和减缓应变累积的备选措施。

Abstract:

To study the structural deformation of the thrust chamber for a liquid oxygen/methane engine under multi-cycle working conditions， a thermo-structural analysis method including fluid-thermal analysis and nonlinear finite element analysis was developed and verified. The thermal and pressure loads on the thrust chamber were obtained by this method， and the stress-strain responses of the thrust chamber under these loads were also investigated. The results show that the overall deformation of the thrust chamber structure is not mainly determined by thermal loads， and the bending of the cooling channel bottom caused by pressure loads is particularly evident in the divergent segment of the nozzle. The elastoplastic tensile strain generated in the post-cooling phase was greater than the compressive strain generated in the hot run phase， which is the direct cause of structural residual strain after each working cycle. As the increasing of the working cycle number， the residual strain accumulation rate at the bottom corner of the cooling channel in the divergent segment was the fastest， and this location was identified as potential location of structural failure. Increasing the bottom thickness of the cooling channel near the coolant inlet， reducing the temperature difference between the post-cooling and the hot run phase， and designing the sharp bottom corners of cooling channels into rounded corners could be the alternative measures to suppress deformation and slow down strain accumulation.