Experimental Investigation on the Adiabatic Film Effectiveness for Counter-Inclined Simple and Laid-Back Film-Holes of Leading Edge

Abstract

The adiabatic film effectiveness η of the counter-inclined film-holes fed by varying internal coolant intake on the turbine vane leading edge model was experimentally investigated. A semi-cylinder model was adopted to model the vane leading edge which was arranged with two-row holes, which located at ±15° on both sides. The four Leading edge model with the combinations of hole-shape (simple holes and laid-back holes) and intake structure (plenum and impingement) were tested under four blowing ratios M of 0.5, 1.0, 1.5, and 2.0. The η contours were obtained by the transient measurement technique based on double thermochromic liquid-crystals. The results present that the η is sensitive to the M for the four studied leading edge cases. The addition of impingement enhances the η for the two studied holes. The film jets make the coolant-flow closed to the target surface, resulting in higher η under lower M. The core with higher η appears in the downstream area of hole-exit. The η enhancement can be provided to almost the identical level by adding the impingement-holes and improving the hole-exit shaping in most areas. With increasing M, the jets with stronger exit normal momentum penetrate into the main-flow. The impingement addition may be a more effective program to upgrade the η relatively to the exit shaping under larger M. Besides, the laid-back holes with impingement case produce the highest film cooling performance among the four cases, providing great potential in the leading edge especially under larger M.