考虑炭化绝热材料膨胀现象的体烧蚀模型
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摘要
针对炭化层厚度大于绝热材料损耗厚度的实验现象,建立了考虑膨胀现象的双区体烧蚀模型。认为膨胀是在热解过程中产生的,且炭化层的生成速率是基体推移速率的2倍。在每一个时间步长根据当地温度与绝热材料热解温度的关系判断炭化层与基体的交界面位置,进行网格重新划分及数据交换耦合计算。结果表明,利用双区体烧蚀模型计算得到的烧蚀率和炭化层孔隙结构与烧蚀实验发动机实验结果相吻合,证明了文中模型能够基本反映EPDM类绝热材料的烧蚀特性。
According to the experimental phenomenon that carbon layer thickness is greater than the insulator matrix loss thickness,a bulk ablation model considering insulator expansion phenomenon with double regions is established.It's believed that expansion is produced during pyrolysis process and the formation rate of carbon layer is 2 times faster than the lapse rate of matrix.At each time step,the interface position of carbon layer and the matrix is determined according to the relationship between local temperature and insulator pyrolysis temperature,and the method of remeshing and data exchange coupling calculation are developed at the same time.The ablation rate and carbon layer porous structure obtained by the double regions bulk ablation model agree well with the experimental results,which proves that the model can basically describe the ablation details of EPDM(ethylene-propylene-diene monomer)insulator.
According to the experimental phenomenon that carbon layer thickness is greater than the insulator matrix loss thickness,a bulk ablation model considering insulator expansion phenomenon with double regions is established.It's believed that expansion is produced during pyrolysis process and the formation rate of carbon layer is 2 times faster than the lapse rate of matrix.At each time step,the interface position of carbon layer and the matrix is determined according to the relationship between local temperature and insulator pyrolysis temperature,and the method of remeshing and data exchange coupling calculation are developed at the same time.The ablation rate and carbon layer porous structure obtained by the double regions bulk ablation model agree well with the experimental results,which proves that the model can basically describe the ablation details of EPDM(ethylene-propylene-diene monomer)insulator.
引文
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[3]Yang B C,Cheung F B,Koo J H.Numercal investigation of thermo-chemical and mechanical erosion of ablative materials[R].[S.l.]:AIAA,93-2045.
[4]Yu I D.Effect of thermo mechanical erosion of heterogeneous combustion of composite materials in high-speed Flows[J].Combustion and Flame,2000,122:211-226.
[5]李强,杨飒,李江,等.EPDM绝热材料耦合烧蚀模型[J].固体火箭技术,2012,35(1):114-117.LI Qiang,YANG Sa,LI Jiang,et al.Coupled ablation model for EPDM insulator[J].Journal of Solid Rocket Technology,2012,35(1):114-117.(in Chinese)
[6]Reynolds R A,Russell G W,Nourse R W.Ablation performance characterization of thermal protection material using a mach 4.4sled test[R].[S.l.]:AIAA,92-3055.
[7]Koo J H.Thermal characteristics comparison of two fire resistant materials[J].Journal of Fire Sciences,1997,15:1027-1032.
[8]Russell G W.Analytic modeling and experimental validation of intumescent behavior of charring heat shield materials[D].Huntsville,Alabama:The University of Alabama in Huntsville,2002.
[9]Clark R K.An analysis of a charring ablator with thermal nonequilibrium chemical kinetics and mass transfer[R].[S.l.]:NASA-TN-D-7180,June,1973.
[10]Ayasoufi A,Rahmani R K,Cheng G,et al.Numerical simulation of ablation for reentry vehicles[R].[S.l.]:AIAA,2006-2908.
[11]William K,Michael C,Bernhard W.Convective heat and mass transfer[M].[S.l.]:McGraw-Hill Inc,1993.