Insights Into the Role of Anti-Counter Rotating Vortices on Film Cooling Efficiency

Cooling techniques are extensively employed to protect turbine components from damage due to extremely high operating temperatures. Despite the availability of multiple cooling geometries, the focus is on investigating the thermal and flow characteristics of cylindrical and fan-shaped injection hole designs. Using a realizable k–ε model, we compare the thermal and flow characteristics of these geometries under identical operating conditions. The research analyzes the impact of vortex interactions and momentum flux ratio on overall (area-averaged) film cooling effectiveness. The study explores the flow structure, vortex interactions, and the effects of blowing ratio (BR = 0.2–2.0) and momentum flux ratio (MR = 0.3–3.5) on film cooling. Additionally, the formation and dynamics of the anti-counter rotating vortex pair (anti-CRVP) in a fan-shaped arrangement are elucidated. The findings indicate that in the fan-shaped case, jet core length is important for enhancing cooling performance. The formation of distinct vortices, such as anti-CRVPs, at higher BRs significantly improves cooling by delaying flow separation. The favorable impact of the anti-CRVP is most pronounced at higher BRs in the fan-shaped configuration. This study also reveals that the geometrical shape of the cooling holes greatly affects the overall film cooling effectiveness, which improves with increasing BR and MR for fan-shaped holes.