炭化层疏松/致密结构的三元乙丙烧蚀模型

分析了烧蚀发动机和高过载烧蚀发动机实验得到EPDM(三元乙丙)的炭化层结构,获得烧蚀过程炭化层结构形成变化的机理,建立了考虑疏松致密结构的多孔炭化层物理模型.模型中炭化层为非均质的多孔可渗透介质,孔隙内部存在气体扩散和热化学反应;炭化层中热解气体沉积效应形成致密结构.在多孔介质流动与传热算法基础上建立了模拟绝热材料烧蚀过程的数值方法,计算得到的炭化率、质量烧蚀率和炭化层的多孔结构与实验结果相吻合,证明了本烧蚀模型能够准确地描述绝热材料的热化学烧蚀过程,并为耦合烧蚀模型的建立提供数值算法基础.

EPDM ablation model considering of porous/compact structure of charring layer

By analyzing the characteristics of charring layers obtained in ablation motor and simulating erosion motor,the forming and consumption mechanisms of charring layer were analyzed,and ablation model considering the porosity of charring layer was developed.With the model,the charring layer was described as gas-saturated porous media with dense layer and porous layer,thermo-chemical reaction and gas diffusion existed in the pores of charring layer,and the compact structure of charring layer was formed by sediment of decomposition gas.Based on numerical investigation on flow and convection in porous media,a numerical model was presented to simulate the ablation process,and the calculated ablative rates,mass loss rates and the structures of charring layer agree with experimental results.The ablation model has been proved to simulate the process of the thermo-chemical ablation reasonably,and to provide the numerical method for all ablation models considering the thermo-chemical ablation and mechanical erosion.