This paper addresses the effect of a favorable streamwise pressure gradient on the velocity field of a single-hole film cooling configuration, operating at unity blowing ratio. The hole is circular and inclined at 30 degrees with respect to the main flow direction. Magnetic Resonance Velocimetry is used to obtain the full three-dimensional field for a baseline configuration with negligible streamwise pressure gradient and for a configuration with favorable streamwise pressure gradient. In the latter case the acceleration parameter is K = 4.8·10−6, which is representative of the conditions along the pressure side of a turbine airfoil. The experiments are performed in water. The velocity and vorticity distributions highlight the strong impact of the favorable pressure gradient on the development of the counter-rotating vortex pair which dominates the dynamics of the film cooling flow. The accelerating flow drives the vortex pair towards the wall, while the increased stretching of the vortices augments their circulation. Both effects contribute to bring the counter-rotating vortices closer to each other. They also persist much further in space with respect to the zero-pressure-gradient case. Implications for the film cooling performance are discussed.
Three-Dimensional Velocity Measurements of Film Cooling Flow Under Favorable Pressure Gradient
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Coletti, F, Elkins, CJ, & Eaton, JK. "Three-Dimensional Velocity Measurements of Film Cooling Flow Under Favorable Pressure Gradient." Proceedings of the ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. Volume 4: Heat Transfer, Parts A and B. Copenhagen, Denmark. June 11–15, 2012. pp. 1627-1638. ASME. https://doi.org/10.1115/GT2012-69402
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