Exploration of Internal Cooling Schemes Enabled Through Additive Manufacturing
Open Access
- Author:
- Corbett, Thomas
- Graduate Program:
- Mechanical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- January 22, 2024
- Committee Members:
- Robert Kunz, Professor in Charge/Director of Graduate Studies
Timothy Simpson, Major Field Member
Allison Beese, Outside Unit & Field Member
Karen Thole, Chair & Dissertation Advisor
Stephen Lynch, Major Field Member - Keywords:
- Heat Transfer
Fluid Dynamics
Internal Cooling
Gas Turbines - Abstract:
- The additive manufacturing (AM) process opens up many opportunities for engineers to explore novel cooling designs that historically may have been costly or even impossible to manufacture. To leverage AM for cooling schemes effectively, engineers must first understand the impact of AM surface roughness on the performance of a variety of internal geometries. The goal of this dissertation was to assess a suite of cooling technologies that were made using AM by comparing the fluid dynamic and heat transfer performance as well as the ability to construct the designs. Specifically, the cooling schemes investigated included wavy channels, pin fin arrays, lattice structures, broken wavy ribs, and diamond pyramid surface features. All of these features were evaluated over a wide range of Reynolds numbers in the turbulent flow regime. The cooling schemes evaluated covered a range of friction factor augmentations from 2 to 500, and heat transfer augmentations between 1.2 and 6 relative to smooth cylindrical channels with no features. The heat transfer and pressure drop of wavy channels was found to be largely a function of the secondary flows with the augmentation scaling as a function of the relative waviness of the channel. Wavy channels were also identified to perform best, in terms of heat transfer, at low Reynolds numbers. Pin fin geometries induced greater heat transfer and pressure loss augmentations than the wavy channels as result of the enhanced surface area and turbulent mixing. Pin shape and spacings were the variables that dictated the pressure loss and heat transfer, though the addition of surface roughness enhanced both flow characteristics. Small surface protrusions such as diamond pyramid turbulators and broken wavy ribs had small performance augmentations relative to the pin fin and wavy channel designs, but these augmentations were found to be insensitive to Reynolds number. The surface features induced substantial near wall mixing with increases in both heat transfer and pressure loss but was further increased as the relative endwall surface roughness increased. Lattice structures had the most significant pressure penalty of all geometries that were considered despite offering only similar heat transfer enhancement to that of the pin fin arrays. Throughout these studies, variations in materials and machines used for the additive manufacturing were identified and related to the performance of internal cooling and pressure loss. These variations led to varying degrees of roughness and a range of surface morphologies. Highly rough wavy channels, for example, significantly increased pressure drop but did not produce an equivalent increase to heat transfer. While arithmetic mean roughness was the primary driver of cooling performance, the surface skewness and kurtosis were found to be key secondary variables. The work presented in this dissertation identified the key flow characteristics and impacts of surface roughness on a variety of internal cooling designs. The data and analyses presented bridge the gap in understanding the performance implications of a range of additively manufactured cooling features empowering designers to integrate new cooling technologies into practical applications.