长尾喷管传热及烧蚀特性研究

Heat Transfer and Ablation Characteristics of Tail-Pipe Nozzle

关键词:  长尾喷管  碳/酚醛  耦合传热  体积烧蚀  表面烧蚀

Key words:  Tail-pipe nozzle  Carbon/phenolic  Conjugate heat transfer  Volumetric ablation  Surface ablation

摘要:

针对长尾喷管的热防护问题，采用实验和数值仿真结合的方法，研究了采用SQ-2推进剂固体火箭发动机复合结构长尾喷管的传热以及烧蚀特性。仿真程序采用基于格心的有限体积法，对流体域求解Navier-Stokes方程，对固体域求解热传导方程，湍流模型采用k-ω SST模型，通过保证热流密度大小相等、温度连续的方法实现耦合传热计算；在以上仿真计算方法的基础上，建立了基于热解动力学的变热物性模型，描述碳/酚醛材料的体积烧蚀，并采用简化的异相反应模型对喷管热化学烧蚀量进行计算。结果表明，在收敛段和等直段区域压强变化较小，炭化层厚度和烧蚀量与温度分布相似， 并在距离等直段入口约1.6mm位置达到极小值。碳/酚醛材料炭化速率随时间减小，烧蚀速率随时间增长趋于稳定，而喉衬区域C/C复合材料烧蚀速率随时间增加。

Abstract:

The investigation of heat transfer and ablation characteristics of tail-pipe nozzle of SQ-2 propellant solid rocket motor is conducted via experimental and numerical approach aiming at the problem of thermal protection of tail-pipe nozzle. The cell centered， finite-volume approach is used to solve the Navier-Stokes equation for the fluid domain and heat conduction equation for solid domain， k-ω SST model is selected for turbulence closure in the simulation program. The conjugate heat transfer process is realized by keeping the heat flux of each side consistent and continuous of temperature on the coupling-wall. On the basis of the above simulation methods， a thermodynamic physical property model based on pyrolysis kinetics is established to describe the volume ablation of carbon / phenolic and the simplified heterogeneous reaction model is used to calculate the thermal chemical ablation of the nozzle. The results indicate that the thickness of charring layer and ablation magnitude is consistent with temperature distribution in axial since pressure changes little in the convergent section equivalent section， and reach a minimum value at a distance of about 1.6 mm from the entrance of the equivalent section.The charring rate decreases with time while ablation rate tends to stabilize over time for carbon/phenolic. The ablation rate grows over time for C/C composite used in the throat insert.