Investigation and Application of Bio-Inspired Microscale Structures to Turbine Endwall for Enhancing Film Cooling Performance

In this paper, inspired by micro-scale surface structure patterns of birds' flight feather, a novel thermal-protection enhancement technique is proposed for a turbine endwall with cavity air leaked from an upstream realistic rim seal. The potential application of the micro-scale surface structures is demonstrated by using well-validated numerical simulations. Overall film cooling performance and total thermodynamic loss are examined to comprehensively evaluate the feasibility of the micro-scale surface patterns for three cavity air flowrates. Detailed thermal fields and flow structures involved in the coolant-mainstream interactions are also presented to reveal physical flow mechanisms behind. Comparisons with a smooth endwall and previously used ribbed endwall cases show that applying the micro-scale structures onto the turbine endwall generates a substantial increase in cooling effectiveness with a very slight aerodynamic penalty. Despite of enhanced heat transfer levels, the resulting heat loads into the endwall are significantly reduced. Detailed thermal fields and flow structures revealed that the addition of the micro-scale structures induces counter-rotating vorticities that mitigate the passage vortex and hence prevents the accumulation of coolant near the suction side. Besides, it is also noted that the grooves of the micro-scale structures have a transport effect that can convey the coolant to the far downstream areas of the endwall, and thus considerably increase the coverage in the chordwise direction. The findings of this work provide an evidence that the bio-inspired, micro-scale surface structures could be an alternative for enhancing turbine endwall cooling performance.