Improvement of film cooling performance by trenched holes on turbine leading-edge models

The present study aims to improve cooling performance over the leading edge surface with the high temperature and high thermal stress by the introduction of trenched holes. Three staggered rows of leading-edge film cooling holes with different trench arrangements and hole orientations are included under blowing ratios of 0.5, 1.0, 1.5, and 2.0, compared with round-hole cases. Under the conditions of leading-edge flow patterns and convex curvature, the trenched hole with 2D width plays a role of "protection" of coolant against the impinging hot gas at a large range of blowing ratios. This contributes to the better lateral spread of coolant and cooling performance. Besides, the trenched holes narrow the regions with a high heat transfer coefficient and reduce the detrimental heating on the surface. Compared with round holes, the trenched holes guarantee the downstream coolant coverage and higher cooling performance at a larger inclined angle, in spite of the changed compound angles.