流固耦合作用下水下点火固体发动机C/C复合材料喷管力学性能分析

Mechanical property evaluation of C/C composite material nozzle of underwater solid rocket motor influenced by fluid-solid coupling

为了研究流固耦合作用对水下点火固体发动机喷管力学性能的影响,采用有限元分析软件建立C/C复合材料喷管的有限元模型,仿真计算不同水深下喷管的力学性能变化。结果表明:真空条件下,喷管的模态频率最大;随着水深增加,流固耦合作用使喷管虚拟质量增大,因而模态频率降低,并且耦合的模态阶数变多。在5~800 Hz振动激励下,随着水深增加,喷管与外界流体发生共振的模态阶数升高,喷管出口部位频率响应的最大位移增大;喷管在5、10、15 m这3种水深下与流体发生流固耦合时的变形云图分布形态一致,只是数值大小不同;但是在15 m水深下,喷管喉部出现严重的应力集中现象,应力值在2.5×107~3.79×1012 Pa之间,存在破坏失效风险。

To evaluate the influence of the fluid-solid coupling on the mechanical properties of C/C composite material nozzle of underwater solid rocket motor,a finite element model is established for simulation analyses for cases in vacuum and underwater in different depths.It is shown that the nozzle has the highest modal frequency in vacuum;while under underwater conditions with the fluid-solid effect,the modal frequency of the nozzle reduces with the increase of the water depth due to the magnified virtual mass,and the number of coupled modes is increased.For the exciting force with a frequency in the range of 5 Hz to 800 Hz,the resonance modal rank of the nozzle increases with the fluid-solid coupling,and the maximum displacement of the vibration response of the nozzle outlet increases with the water depth.The displacement distributions of the nozzle are in a similar shape for different depths of water,with only numerical drifts;however,the stress concentration is found on the throat part of the nozzle in the case of underwater in 15 m depth,with a local stress of 2.5×107 Pa to 3.79×1012 Pa,indicating a risk of destructive failure of the nozzle in the actual case.