Effects of Geometry on Slot–Jet Film Cooling Performance

Abstract

The physics of the film cooling process for shaped, inclined slot–jets with realistic slot–length–to–width ratios (L/s) is studied for a range of blowing ratio (M) and density ratio (DR) parameters typical of gas turbine operations. The effect of inlet and exit shaping of the slot–jet on both flow and thermal field characteristics is isolated, and the dominant mechanisms responsible for differences in these characteristics are documented. A previously documented computational methodology was applied for the study of four distinct configurations: (1) slot with straight edges and sharp comers (reference case); (2) slot with shaped inlet region; (3) slot with shaped exit region; and (4) slot with both shaped inlet and exit regions. Detailed field results as well as surface phenomena involving adiabatic film effectiveness (η) and heat transfer coefficient (h) are presented. It is demonstrated that both η and h results are vital in the proper assessment of film cooling performance. The key parameters M and DR were varied from 1.0 to 2.0 and 1.5 to 2.0, respectively, to show their influence. Simulations were repeated for slot length–to–width ratio (L/s) of 3.0 and 4.5 in order to explain the effects of this important parameter. The computational simulations showed exceptionally strong internal consistency. Moreover, the ability of using a state–of–the–art computational methodology to sort the relative performance of different slot–jet film cooling configurations was clearly established.