Session: 15-07: Numerical Studies of Internal Cooling

Submission Number: 175719

Investigation of Roughness Effects on Heat Transfer and Flow Resistance in Turbine Blade Microchannels 

Turbine-blade internal microchannels achieve efficient internal cooling through a high surface-area-to-volume ratio; however, manufacturing-induced random surface roughness and regular roughness introduced by turbulators such as ribs increase pressure drop and complicate heat-transfer distribution, necessitating a quantitative assessment of roughness effects on flow and heat transfer. In realistic-scale microchannels, the area-averaged Nusselt number (Nu) and pressure coefficient (Cp) are measured experimentally, and Reynolds-averaged Navier-Stokes computational fluid dynamics is employed to resolve near-wall flow structures and heat-transfer mechanisms; the effects of multiple levels of random roughness and rib-induced regular roughness are systematically assessed. Results show that the influence of roughness on heat transfer increases with Reynolds number (Re). Relative to a smooth passage, the configuration with a V-rib placed upstream of film-cooling holes delivers the strongest augmentation; at Re = 42,000, the area-averaged Nu and Cp increase by 66.22% and 14.06%, respectively. For random roughness, effects are negligible when Ra/h <= 1% but become significant at Ra/h >= 5%, accompanied by a rapid increase in Cp. Suction through the film-cooling holes disrupts the boundary layer and deflects the mainstream toward the wall, thereby enhancing heat transfer. Rib-induced roughness promotes reattachment of the separated shear layer on the downstream base wall on the ribbed side and, together with secondary flows, broadens the high-Nusselt-number region; random roughness triggers crest-to-trough micro-separation and recirculation, enlarges near-wall high-shear regions, and increases wall shear and form drag, so thermal gains come with a higher pressure-drop penalty.

Presenting Author: Ke Li Northwestern Polytechnical University

Presenting Author Biography: Ke Li is a graduate student in the School of Power and Energy at Northwestern Polytechnical University, Xi’an, China. His research focuses on effects of roughness on heat transfer and flow resistance in turbine-blade internal microchannels.

Authors:

Ke Li Northwestern Polytechnical University
Tao Guo Northwestern Polytechnical University
Guodong Li Northwestern Polytechnical University
Changwei Li TaiHang Laboratory
Wenchao Wang Northwestern Polytechnical University
Cunliang Liu Northwestern Polytechnical University
Lin Ye Northwestern Polytechnical University