Effect of Morphological Variations in TPMS Lattice Structures on Transpiration Cooling

Abstract The development of advanced cooling technologies for modern aero engines has become essential to protect critical gas turbine components, such as the combustion chamber, from increasing combustion temperatures and to extend their operational lifespan. Among cooling techniques, transpiration cooling stands out due to its notable merits, including efficient heat exchange on extensive internal surface areas between the porous solid networks and the cooling fluid, as well as the formation of an effective and uniform cooling film on the wall surface without lift-off. However, the performance of transpiration cooling relies on the precise control of pore size to ensure uniform film cooling distribution across the entire surface and to prevent the formation of localized hot spots. Recent advancements in additive manufacturing (AM), commonly known as 3D printing technology, have enabled the fabrication of lattice-based deterministic porous media with precisely controlled pore sizes and distributions. Among the various lattice structures used in transpiration cooling systems, Triply Periodic Minimal Surfaces (TPMS) have drawn significant attention due to their high performance and periodic characteristics, which can be precisely controlled. The potential of transpiration cooling using this family of lattice geometries has been demonstrated in our previous studies. However, optimizing transpiration cooling with TPMS lattice-based porous media in real gas turbine components remains challenging. Complex geometric features of engine components, including surface curvatures and variations in component thickness, lead to morphological variations in surface texture and the orientation of surface void patterns, which can significantly affect the performance of transpiration cooling. Given the geometry complexity of engine hot-gas path components, it is impractical to make location-specific variations to the TPMS lattices to precisely control the resulting surface texture of prescribed pattern and orientation. This study investigates experimentally how film cooling effectiveness is affected by the use of different types of TPMS lattices that expose varying cross-sections of a TPMS lattice as the top surface with changing surface texture pattern and orientation. The goal is to understand how these cross-section variations affect transpiration cooling performance and to identify TPMS geometries that are ideally insensitive to such variations. Three types of TPMS structures, namely Diamond, Koch, and Gyroid, were selected to develop a design principle for choosing TPMS types for transpiration cooling that are least sensitive to variation in surface texture resulting from complex geometries. The Pressure Sensitive Paint (PSP) technique was employed for assessing resulting film cooling effectiveness.