烧蚀型热防护系统概率设计与可靠性评估方法研究

Probabilistic design and reliability assessment methods for ablative thermal protection systems

为在保障热防护系统可靠性的前提下减轻重量,本文建立考虑多源不确定性的烧蚀型热防护系统的概率设计和可靠性评估方法。采用有限元方法计算系统热响应,通过试验测试与数值模型对比验证方法的有效性。并构建热防护系统的不确定性输入参数与目标输出的代理模型,基于代理模型与蒙特卡洛方法进行热防护系统目标变量的概率特性分析。采用Sobol指标对不确定性参数进行灵敏度分析,并以系统可靠性为指标进行概率设计。该方法针对来流、几何以及材料属性等多源不确定性进行热防护系统的概率设计与可靠性评估,以二维平板模型为例,计算热防护系统最高背温的概率特性以及不确定性参数的灵敏度,得到了不同涂层厚度情况下系统的可靠性。结果表明,与安全系数 n =1.5的设计相比,概率设计减重达到24%。

In order to reduce the weight on the premise of ensuring the reliability of a thermal protection system,a probabilistic design and reliability evaluation method for an ablative thermal protection system considering multi-source uncertainties is established in this paper.The finite element method is used to calculate the thermal response of the system,and the validity of the method is verified by comparing the experimental test with the numerical model.A surrogate model for the uncertain input parameters and target output of the thermal protection system is constructed,and the probability characteristics of the target variables of the thermal protection system are analyzed based on the surrogate model and the Monte Carlo method.The sensitivity analysis of uncertainty parameters is carried out by using Sobol index,and the probability design is carried out by taking system reliability as an index.In this method,the probabilistic design and reliability evaluation of thermal protection systems are carried out for multi-source uncertainties such as flow,geometry and material properties.Taking the two-dimensional plate model as an example,the probability characteristics of the maximum back temperature of the thermal protection system and the sensitivity of the uncertainty parameters are calculated,and the reliability of the system under different coating thicknesses is obtained.The results show that,compared with the design with safety factor n =1.5,the probabilistic design achieves 24% weight reduction.