Most film cooling experiments in open literature study the effectiveness downstream of ideally-manufactured holes in the laboratory setting. The manufacturing processes for real gas turbine components, however, produce anything but ideal film cooling hole shapes. This study investigates the effect of geometric deviations associated with manufacturing techniques on the effectiveness downstream of a row of cylindrical holes. The holes have an inclination angle of 30 degrees with no span-wise angle. The holes were manufactured into test coupons fabricated from engine super-alloys using four different hole-manufacturing techniques. Each coupon was manufactured under actual manufacturing conditions for turbine components and the actual hole size found in the engines was used. The test coupons consisted of a row of 20 cylindrical holes. The manufacturing techniques were compared in terms of area ratio from hole inlet to exit, effective area, and film cooling effectiveness on the downstream surface. A complimentary three-dimensional conjugate computational fluid dynamics study was performed using Fluent 6.0 software to help account for the heat pickup through the coolant holes in the super-alloy coupons and to compare against experimental data on the downstream surface. It was found that the manufacturing technique can have a noticeable effect, either negatively by the impedance of irregularities or positively by creating a diffusion-shaped 'cylindrical' hole. The variation in effectiveness due to manufacturing was found to be more exaggerated at higher blowing ratios.
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