八面体桁架结构在内冷通道中的流动传热特性研究

为探究八面体桁架结构在航空发动机热端部件内冷通道中的可应用性，掌握八面体桁架结构的流动传热特性，本文采用理论推导和三维数值模拟的方法，对八面体桁架单体的有效导热系数以及八面体桁架阵列结构的流动结构和传热性能开展了研究。首先，针对八面体桁架单体结构，推导出了考虑节点效应的有效导热系数关系式，并通过与数值计算结果对比，验证了其有效性。其次，针对八面体桁架阵列结构，开展了整体结构的三维数值计算，分析了其内部通道的流动结构和温度分布，获得了不同结构的流动阻力和对流传热系数随雷诺数的变化规律。最后，考虑到结构的综合传热性能，本文针对不同孔隙率的八面体桁架阵列结构，进行了基于相同泵功率下努塞尔数的对比。根据计算结果，本文给出了获得最佳传热性能的无量纲直径范围0.07~0.08，相应的孔隙率变化范围 0.872~0.841。分析其原因，由于随着结构孔隙率的减小，即固体率的增加，对流传热强度不断提高，然而，当孔隙率减小到84.1%以下时，由于内通道中流动阻力骤然增大，导致传热效率降低。将八面体桁架结构应用于航空发动机热端部件内冷通道中，是同时出于高效冷却和力学性能的考虑，本文掌握八面体桁架阵列结构的流动传热特性，为其在实际工程中的应用提供了理论支撑。

Flow and Heat Transfer Characteristics of Octet Truss Structure in Internal Cooling Channel

In order to explore the possibility of application of the octet truss structure in internal cooling channel in hot components of aeroengine, understand its flow and heat transfer characteristics, in this study, the investigations both on effective thermal conductivity of an octet truss element and fluid structure and heat transfer performance of octet truss array structure have been carried out by exploiting methods of theoretical derivation and three-dimensional numerical simulation, respectively. First of all, the correlation of effective thermal conductivity which considers nodal effects has been derived out for an octet truss element, moreover, its effectiveness has been validated by comparing with numerical result. Subsequently, a series of full-detailed three-dimensional calculations has been carried out for octet truss array structure, in which the flow structure and temperature distribution have been analyzed, furthermore, the variation of friction factor and heat transfer coefficient with Reynolds number have been obtained. Finally, in consideration of heat transfer performance of the octet truss structure, in this study, the Nusselt numbers for octet truss structures with different porosity have been compared under equal pumping power. As a result, a reasonable range of dimensionless diameter which leads to an excellent heat transfer performance has been proposed as 0.07~0.08, whose corresponding porosity ranges in 0.872~0.841. The reason may be concluded that the heat transfer rate increases with the decrease of porosity, i.e., the increase of the solidity. However, when the porosity decreases to below 84.1%, the friction factor increases drastically, leading to the decrease of overall heat transfer efficiency. The proposal of the utilization of the octet truss in internal cooling channel in hot end components of aeroengine considers the advantages both of higher efficient cooling and mechanical performance. The result is helpful to provide theoretical support for application in practical engineering.