Strength Analysis And Structure Optimization Of Composite-Structure Nozzle

In this paper,a pin connected to the composite-structure nozzle was investigated in terms of its intensity analysis and structural optimization design.The structure is characterized in that when the abnormal working of the engine causes the pressure in the combustion chamber higher than the limitation of the shell material strength,the pin at the nozzle connection breaks down first,and the nozzle is then thrown out to broaden the gas passage area for the combustion products to be rapidly ejected,which can effectively protect the launch site.The finite volume method was used to calculate the flow field in the nozzle.The strength of the connection between the long tail pipe and nozzle pinas well as that between the combustion chamber and long tail pipe were analyzed with finite element method.Besides,this paper did the transient thermal analysis,thermal-structural coupling analysis with sequential coupling method,and optimization design and sensitivity analysis of nozzle shell using response surface method.The main work is as follows:1)The functional relationship of the axial distance between the temperature and the pressure on the inner wall of the nozzle was analyzed.The results show that the temperature and pressure in the axial direction of the trend is about the same,with the relationship between the axial distance being non-linear and showing a downward trend in the laryngeal nozzle position.There is a gentle phase,and then in the throat and expansion Section of the junction of significant changes in the sudden,is an important factor for the nozzle strength analysis.2)The strength of the bond between the pin and the combustion chamber structure of the composite nozzle was analyzed,and the stress field distribution was obtained,based on which the maximum pressure load of the structure was explored.The results show that the maximum stress value of the composite-structure nozzle appears on the connecting pin,which is higher than the value of the stress field at the connection key and less than the material strength limit.At the combustion chamber pressure produced at the normal working of the engine,the structure remains intact;while the pressure increases by 17.4%,the stress of the pin reaches the maximum strength and caused the structure damage.The structure of the combustion chamber shell,the long tail pipe shell and the connecting part after the hydrostatic test remains intact,and no significant deformation occurs,indicating that the structure meets the strength requirement.3)The transient thermal analysis and thermo-structural coupling analysis of the structure were respectively carried out.The influences of temperature and pressure load on the structural stress and deformation were also considered.The results show that there is no significant change in the maximum stress position of the whole composite pipe and each component.When the maximum stress value of the connecting pin increases,the stress concentration increases.The temperature load has little effect on the deformation of the nonmetallic material,but more on the material deformations.4)The nozzle shell design was optimized.The results show that the size of the end of the tail pipe shell is the smallest and that of the nozzle shell is the most optimal.The total mass of the nozzle shell reduces by 0.01 kg and the optimization efficiency is 2.7% Thickness has the greatest impact on the total mass of the nozzle,and the thickness of the end wall of the long tail pipe shell has the greatest influence on the maximum stress of the nozzle shell.