Repeatability in Performance of Micro Cooling Geometries Manufactured with Laser Powder Bed Fusion

Abstract

Stringent regulations on aircraft engine emissions introduce a series restrictions on weight, size, and durability of all engine components to increase efficiency. In the hot section of a gas turbine engine, for example, airfoil internal cooling schemes must provide more efficient cooling with minimal mass flow. Such a requirement drives the cooling channels' size to the micro scale. One new tool currently being explored to achieve industry-required efficiencies can be found in advanced manufacturing techniques, such as laser powder bed fusion. However, as with all new technologies, the laser powder bed fusion process must be thoroughly investigated, fully understood, and achieve reliable and repeatable results before the process is widely implemented for gas turbine airfoils. This paper provides experimental results on the dimensions, as well as pressure loss and heat transfer performance, of microchannels manufactured using laser powder bed fusion; the microchannels mimic those suitable for airfoil internal cooling. Variability in the performance will be quantified for different builds, as well as for different materials. Nomenclature AM Additive manufacturing As surface area CT X-ray computed tomography Dh hydraulic diameter f friction factor, ΔP•(1/2•ρ•U2)-1 •Dh•L-1 h heat transfer coefficient, Q•(As•ΔTlm)-1 k thermal conductivity L-PBF laser powder bed fusion Nu Nusselt number, h•Dh•k-1 Re Reynolds number, U•Dh•ν-1 ΔTlm log mean temperature difference U mean channel velocity ϵ sand grain roughness λ wavelength ν kinematic viscosity I. Introduction The potential of metal additive manufacturing (AM) to transform the aerospace industry is limitless. Key benefits of the manufacturing technology include weight, material, and lead time savings, in addition to a more open design space well-suited to shape and topology optimization. Despite the continual improvements in the industry, however, the manufacturing method requires further vetting, especially in the realm of geometric repeatability and holding tolerances of micro-sized features.

Full-Density Fused Deposition Modeling Dimensional Error as a Function of Raster Angle and Build Orientation: Large Dataset for Eleven Materials

“…However, there are some limitations and problems that need to be considered and addressed when using AM, dimensional accuracy [16,17], process and geometric repeatability [18][19][20], and material defects [21][22][23] being the primary considerations. While all are important considerations, the most essential from the perspective of engineering design are the dimensional accuracy and repeatability of the final parts.…”

Effect of Additive Manufacturing Process Parameters on Turbine Cooling

“…4. The overall architecture of these coupons was first introduced in previous studies by the current author [4,5] and has been utilized in numerous other studies [15,[27][28][29][30][31] from the same research group. In this geometry, rectangular cooling channels pass through a 25 × 25 × 3 mm block of material, with flanges on the ends that mate with the test rig.…”

Full-Density Fused Deposition Modeling Dimensional Error as a Function of Raster Angle and Build Orientation: Large Dataset for Eleven Materials

“…However, there are some limitations and problems that need to be considered and addressed when using AM, dimensional accuracy [13,14], process and geometric repeatability [15][16][17], and material defects [18][19][20] being the primary considerations. While all of these are important to examine, the most important from the perspective of engineering design are the dimensional accuracy and repeatability of the final parts.…”