碳/酚醛复合材料烧蚀行为预报方法

为研究用于钝头体高超声速飞行器热防护系统的碳/酚醛复合材料在典型服役环境下的烧蚀机制,首先,建立了烧蚀行为的数学模型,模型考虑了材料表面热辐射、固体相的温升吸热、基体热解反应吸热、高温热解气体引射、质量引射引起"热阻塞"效应、热解气体的温升和膨胀吸热等多种能量耗散机制,并利用有限元方法实现了数学模型的求解;然后,预报了在冷壁热流为400 kW·m-2、焓值为5 MJ·kg-1的气动热环境下碳/酚醛复合材料的烧蚀行为。结果表明:在受热过程中,厚度为20 mm的碳/酚醛复合材料碳化层的深度持续增加, 100 s时的表面温度达到1420 K,背壁温度为346 K,热解气体压力达10.3 atm,碳化层深度为7.50 mm。所得结论可为具有长时间大面积热防护需求的高超声速飞行器的热防护系统设计提供支持。 

Forecasting method for ablation behaviors of carbon/phenolic composites

In order to investigate the ablation mechanisms of carbon/phenolic composites which were used in ther-mal protection system of hypersonic vehicles with blunt shapes,the mathematical model for ablation behavior was established firstly,the model took a variety of energy dissipation mechanisms,including the thermal radiation of ma-terial surface,the heat absorption of the solid phase by temperature rise,the heat absorption of matrix pyrolysis re-action,the ej ection of high temperature pyrolysis gas,“heat block”effect caused by mass ej ection,temperature rise and heat absorption by expansion of pyrolysis gas etc.,into account,and the solving of mathematical model was re-alized by finite element method.Then,the ablation behaviors of carbon/phenolic composites under aerodynamic heating environment that cold wall heat flux was 400 kW·m-2 and enthalpy was 5 MJ·kg-1 were forecasted.The results show that during heating period,the depth of carbonized layer in carbon/phenolic composite whose thickness is 20 mm increases continually,the surface temperature reaches 1 420 K and the rear wall temperature is 346 K at 100 s,the pyrolysis gas pressure arrives 10.3 atm and the depth of carbonized layer is 7.50 mm.The conclusions obtained can provide supports for the design of thermal protection system in hypersonic vehicles which have long-time and large area thermal protection requirements.