颗粒冲刷条件下硅橡胶绝热材料烧蚀特性实验研究

Experimental Investigation on Ablation Characteristic of Silicone Rubber Insulator under Particle Erosion Condition

关键词:  固体火箭发动机  硅橡胶  绝热层  烧蚀特性  烧实验

Key words:  Solid rocket motor  Silicone rubber  Insulator  Ablation characteristic  Experiment

摘要:

为了研究颗粒冲刷条件下硅橡胶绝热材料的烧蚀规律和特性，采用一种颗粒冲刷状态可调的实验发动机，以添加有短切碳纤维和高硅氧玻璃纤维的硅橡胶为研究对象，开展了颗粒聚集浓度范围为34.5～75.3kg/m3，冲刷速度为9.4～35.9m/s，角度为19.3°～55.5°条件下的13次热试车实验，获得了颗粒冲刷状态参数和炭化烧蚀率之间的宏观影响规律，通过对试验后试件的宏观形貌和微观结构特征进行分析，初步探讨了硅橡胶绝热材料的烧蚀机理。研究结果表明:(1)和EPDM绝热材料的烧蚀规律和特性不同，实验条件下硅橡胶炭化层更厚且致密，硅橡胶材料的最大烧蚀率随颗粒聚集浓度变化较为敏感，当超过50kg/m3临界浓度值时，烧蚀率随浓度的增加而急剧增大。最大烧蚀率随颗粒冲刷速度增加而增大，并呈现出先急剧增加后缓慢增加的趋势；(2)在颗粒冲刷速度较低条件下，硅橡胶材料烧蚀率要高于EPDM的，在颗粒冲刷速度较高条件下，硅橡胶耐冲刷性能要略优于EPDM的；(3)硅橡胶的热分解温度区间约为623～989K，在烧蚀过程中，高硅氧纤维和硅橡胶分解产生的SiO₂会渗透到炭化层骨架中，进一步和C反应形成SiC，从而使炭化层致密化，具备耐冲刷特性；(4)通过分析烧蚀形貌和微观特征，初步提出了三层一面(基体层，热解层，炭化层，冲刷面)的烧蚀物理模型。

Abstract:

Focused on the ablation characteristics of silicone rubber enhanced by chopped carbon and high silica glass fiber under high temperature and concentration particle erosion condition，thirteen hot firing ablation experiments which range of particle concentration，erosion velocity and angles are 34.5～75.3kg/m3，9.4～35.9m/s，19.3°～55.5°，respectively，have been performed on test motor. The ablation rates of silicone rubber insulator have been obtained under different particle erosion condition. Based on the results of ablation rate and character of the insulator，the ablation mechanism of silicone rubber insulator under particle erosion condition has been discussed. The results show that: (1) compared with the EPDM ablation results，the char layer of the silicone rubber insulator is more dense and thick than EPDM’s，and the maximum ablation rates of the silicone rubber insulator are sensitive with the change of the particle concentration. When particle concentration is beyond 50kg/m3 of the particle concentration，the ablation rate increases sharply. And with increasing of particle erosion velocity，the ablation rate of silicon rubber insulator increases acutely at first and then increases slowly. (2) Under low particle erosion velocity condition，the ablation rates of EPDM were lower than silicon rubber’s，but under high particle erosion velocity condition，the ablation rates of EPDM were higher than silicon rubber’s. (3)The pyrolysis interval of silicone rubber is about 623～989K. During the ablation process，SiO₂ produced by pyrolysis of high silica glass fiber and silicon rubber will permeate into the porous of char layer，and will react with the C in char layer to form the SiC. Then the char layer is densified and can endure particle erosion. (4)Through the morphology observation and analysis，the ablation physics model of silicon rubber insulator with three-layer and one-surface ablation structure (original layer，pyrolysis layer，char layer，particle erosion surface) is put forward.