高温金属3D打印的晶格阵列冷却结构在热端部件中的传热机械性能研究

Lattice Cooling is a new and promising approach to protect hot-section components, such as the first stage turbine airfoils or combustor liners. These components are subject to immense thermal-mechanical loads and critical to the advances for modern aircraft engines and land-based, power generation gas turbines. Lattice structures for advanced cooling enhancement are usually three-dimensional, of very high surface-to-volume ratios, and with fine-scale surface features. Hence to fabricate such complex geometry with highly resilient, high-temperature material, utilization of conventional subtractive-based manufacturing processes and/or casting are extremely difficult, if not impossible. Recent advances in metallic additive manufacturing (AM) processes, such as selective laser melting or binder-jet sintering, offer enormous potential in realizing lattice-structure based heat exchangers. While the approach of using AM for lattice structure fabrication is innovative and novel, the scientific knowledge of both metal-based AM processes and heat transfer mechanism associated with lattice structures is very limited and still requires an immense level of fundamental research. Fabricating lattice cooling structures using metallic additive manufacturing and high temperature superalloy is an interdisciplinary challenge which involves issues in metallurgy, inspection, heat transfer and mechanical properties. This proposed project targets at fabricating and characterization of advanced lattice cooling structures using the powder-bed fusion metallic additive manufacturing technology and realistic high-temperature superalloys. While the scope of this research is highly interdisciplinary, which involves material selection, processing and manufacturing, systematic investigation will be directed to analyzing the heat transfer, pressure drop and mechanical properties of lattice structures. Special focus will be placed on the scientific exploration of the lattice geometry the scaling effects on the transport phenomena. In addition, multidisciplinary model for additive manufactured lattice structures can thus be developed based on the experimental and numerical results. Knowledge gained from this research and rendered impacts will not only significantly advance the turbine cooling technology but tremendously benefit the general heat exchanger community and industry.

新一代的飞机发动机或地面发电燃气轮机面临严酷的热-机械载荷。晶格阵列结构通常具有很强的三维特性、高的面积体积比、以及微细的内部结构，使其在热端部件冷却方面拥有巨大潜力。然而，利用传统的减材加工方式制造这类高复杂度的结构相当困难。近年来，金属增材制造技术的兴起使得利用高温合金加工晶格阵列冷却成为可能，但此技术仍面临传热、冶金、检测和机械性能等多学科的挑战。本项目拟采用粉末床选择性激光烧结的金属3D打印技术和常用的高温合金，制造和测试先进晶格阵列冷却结构，系统地研究晶格阵列结构的传热、压损和机械性能，同时少量兼顾材料选择和加工问题。本项目的着眼点将放在探索晶格类型和晶格尺度效应两个方面，通过大量实验和数值研究，进一步发展晶格阵列冷却结构的多学科优化模型。项目研究成果预期可以推动涡轮冷却技术和传热强化技术的共同进步，同时也大大提升先进热交换器的设计和技术。

周期性多孔材料的典型代表—点阵结构（晶格阵列），在具有良好力学性能的同时，兼具高表体比和高强度的扰流效果，在热端部件冷却和热交换器设计方面展现出巨大潜力。本项目从桁架型点阵结构和三周期极小曲面(Triply periodic minimal surface, TPMS)点阵结构出发，综合运用3D打印、材料表征、流动传热测试和数值模拟等手段，研究其扰流作用机理、传热性能、力学性能及优化设计。项目主要研究成果有：1）揭示了典型点阵结构的壁面传热发展规律，总结了点阵结构诱发的复杂涡系及其与传热强化特性的内在联系；2）评估了金属3D打印微小点阵结构的成型精度和表面形貌，分析了小尺度金属点阵通道的流动传热性能及各部分的传热贡献比例；3）基于人工神经网络和遗传算法提出了一种限定体积条件下的点阵通道流动传热性能的优化设计方法; 4）建立了TPMS点阵结构的高精度模型设计方法，揭示了其压缩变形机制和流动换热机理，并评估了其作为新型紧凑高效换热器单元的应用前景。本项目的工作总结了典型点阵结构的流动传热和机械性能，为涡轮叶片新型高效冷却结构的设计及先进热交换器的开发提供了指导。