Evaluating the Effects of Internal Impingement Cooling on a Film Cooled Turbine Blade Leading Edge

Abstract

The main goal of this work was to evaluate the influence of impingement cooling on the cooling performance on a film cooled turbine blade leading edge. Cooling performance was quantified in terms of overall effectiveness, i.e. the normalized external surface temperature. Numerical simulations, using the commercial code FLUENT, were carried out for a leading edge model corresponding to an experimental model tested previously. The leading edge geometry consisted of three rows of holes positioned along the stagnation line and at ±25°. Three different impingement plate configurations were investigated. Two impingement plate configurations had a single row of holes along the center so that the impingement jets were directed on the stagnation line in between coolant hole entrances. These configurations had varying hole diameters such that impingement jet velocity varied by a factor of two. The third impingement plate configuration had two rows of holes with each row was placed in between the coolant hole entrances along the off stagnation lines. A configuration with no impingement plate was also investigated. For these simulations the realizable k-ε turbulence model was used. All experimental conditions were matched including the density ratio of 1.5 and blowing ratios of 1.0 and 2.0. The numerical simulations were consistent with experiments in showing that the overall effectiveness was only slightly improved by the impingement cooling. This small effect on overall effectiveness was shown to be due to conjugate effects including a reduction of convective cooling within the coolant holes when impingement cooling was used.