Heat Transfer Measurements and Comparisons for a Film Cooled Flat Plate with Realistic Hole Pattern in a Medium Duration Blowdown Facility
Recent advances have for the first time made it possible to perform experiments using fully-cooled rotating turbine stages operating at design-corrected conditions. These experiments produce realistic measurements of the time-averaged and time-accurate local heat transfer for the stage. Despite the value of these results, however, it is still not possible to provide full-coverage measurements due to the difficulties inherent in the view angle and instrumentation of a rotating turbine. Computational simulations show promise in filling in these gaps, but these calculations are not yet able to accurately model the complicated flow physics of these experiments.Experiments utilizing simplified geometries, the most common being a flat plate with a single row of cooling holes, have been run for decades and reported in the literature in literally thousands of papers. They have given valuable insight regarding the more fundamental aspects of film cooling, and the results of these works are used by the industry (with some proprietary modifications) in the design of current engine hardware. These experiments succeed in showing the influence of individual variables with a good deal of detail and clarity; however, due to excessive geometric simplification, the results of these studies fail to capture important flow characteristics observed in data from rotating experiments.In an attempt to help bridge the gap between the common single and double-row flat-plate experiments and the fully cooled rotating experiments, a flat-plate experiment is performed using a medium-duration blowdown facility with a real cooling hole pattern representative of the pressure side of a high-pressure turbine blade. A computational prediction for the experiment is also performed and presented. New heat transfer and film cooling performance parameters are defined for use in the unsteady blowdown facility. Measurements are made to investigate the influence of blowing ratio spanning the range of interest to industry. These results are compared to both simplified hole pattern experiments and rotating experiments to help quantify the effect of the simplified patterns used in the majority of film cooling experiments. Finally, lessons for future experimentation at The Ohio State University Gas Turbine Laboratory are outlined.
Aerospace Engineering, Mechanical Engineering, film cooling, flat plate, heat transfer, realistic hole pattern, CFD, gas turbine
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