Improving Purge Air Cooling Effectiveness by Engineered End-Wall Surface Structures—Part I: Duct Flow

Abstract

Motivated by the recent advances in additive manufacturing, this study investigated a new turbine end-wall aerothermal management method by engineered surface structures. The feasibility of enhancing purge air cooling effectiveness through a series of small-scale ribs added onto the turbine end-wall was explored experimentally and numerically in this two-part paper. Part I presents the fundamental working mechanism and cooling performance in a 90 deg turning duct (part I), and part II of this paper validates the concept in a more realistic turbine cascade case. In part I, the turning duct is employed as a simplified model for the turbine passage without introducing the horseshoe vortex. End-wall heat transfer and temperature were measured by the infrared thermography. Computational fluid dynamics (CFD) simulation was also performed using ANSYS fluent to compliment the experimental findings. With the added end-wall rib structures, purge air flow was observed to be more attached to the end-wall and cover a larger wall surface area. Both experimental and numerical results reveal a consistent trend on improved film cooling effectiveness. The practical design optimization strategy is also discussed in this paper.