双脉冲固体发动机燃烧室EPDM绝热层烧蚀性能实验研究

双脉冲发动机工作时燃烧室内部热环境复杂，对内绝热层设计提出很高要求，但对双脉冲发动机燃烧室内EPDM绝热层的烧蚀性能研究较少。为此，本文提出了工作时间为15s和两次点火工作时间为7.5s+7.5s的发动机实验方案，以研究双脉冲固体发动机燃烧室内EPDM绝热层的烧蚀性能。采用SEM电镜扫描、微米CT测试分析获得了烧蚀试件的表面宏观形貌、炭化层表面和断面微观形貌以及炭化层三维构型；利用测厚仪测量结果计算了试件的烧蚀率。结果表明，在总工作时间相等的情况下，双脉冲发动机中EPDM绝热层的烧蚀率比传统发动机大；与传统发动机中单次热冲击下烧蚀后试件相比，双脉冲发动机二次热冲击下烧蚀后试件的炭化层厚度减小约50%，总体孔隙率增大约13%；烧蚀表面致密层的致密程度也有所减小。双脉冲发动机工作时，EPDM绝热层的烧蚀性能在二次热冲击下发生较大变化，需在燃烧室内绝热层的设计过程中予以重视。

Experimental Study on Ablation Performance of EPDM Insulation Layer in Combustion Chamber of Dual Pulse Solid Rocket Motor

The thermal environment of the combustion chamber of the dual pulse engine is complex, which puts forward high requirements for the design of the internal insulation layer. However, the ablation performance of the EPDM insulation layer in the combustion chamber of the dual pulse engine is less studied. In order to study the ablation performance of EPDM insulation in the combustion chamber of a double-pulse solid engine, an engine experiment scheme with working time of 15s and two ignition of 7.5s+7.5s was proposed. The surface morphology of the ablation specimen, the surface and section morphology of the carbonized layer and the three-dimensional configuration of the carbonized layer were obtained by SEM scanning and micron CT testing. The ablation rate of the specimen was calculated by the measurement results of the thickness gauge. The results show that the ablation rate of the EPDM insulation is higher than that of the conventional engine under the same total working time. Compared with the specimens in the traditional engine after a single thermal shock, the thickness of carbonization layer decreases by 50% and the overall porosity increases by 13% after a double pulse engine after a second thermal shock. The density of the dense layer on the ablation surface also decreases. The ablation performance of EPDM insulation varies greatly under the secondary thermal shock when the double-pulse engine is in operation, which should be paid more attention to in the design process of the insulation in the combustion chamber.