An experimental and computational investigation was conducted on the film cooling adiabatic effectiveness of a flat plate with full coverage film cooling. The full coverage film cooling array was comprised of ten rows of coolant holes, arranged in a staggered pattern, with short L/D=1, normal coolant holes. A single row of cooland holes was also examined to determine the accuracy of a superposition prediction of the full coverage adiabatic effectiveness performance. Large density coolant jets and high mainstream turbulence conditions were utilized to simulate realistic engine conditions. High-resolution adiabatic effectiveness measurements were obtained using infrared imaging techniques and a large-scale flat plate model. Optimum adiabatic effectiveness was found to occur for a blowing ratio of M=0.65. At this blowing ratio separation of the coolant jet immediately downstream of the hole was observed. For M=0.65, the high mainstream turbulence decreased the spatially averaged effectiveness level by 12 percent. The high mainstream turbulence produced a larger effect for lower blowing ratios. The superposition model based on single row effectiveness results over-predicted the full coverage effectiveness levels.

The influence of a high mainstream turbulence was examined in an experimental study of film cooling on a simulated turbine blade leading edge. Detailed heat transfer coefficient and adiabatic effectiveness values were measured under conditions representative of actual environments in a gas turbine engine. The two parameters were also combined for a net heat flux reduction analysis. Turbulence levels of Tu = 17% were achieved by modifying a cross-jets turbulence generator with a large cylinder element. A quarter cylinder geometry was used to simulate the turbine blade leading edge. Two staggered rows of nine holes each were incorporated with a geometry consistent with current industry design practices. One row was positioned nominally on the stagnation line, x/d = 0, while the other was located 25° from the stagnation line. The holes were spaced at S/d = 7.64 with a shallow injection angle of 20° and oriented at 90° to the streamwise direction. Comparisons were made to previous studies of heat transfer rates and adiabatic effectiveness values under low turbulence (Tu < 0.5%) conditions. Adiabatic effectiveness was generally decreased by about 20% due to the high mainstream turbulence, although a much greater decrease occurred at the stagnation line at lower blowing rates. The relative increase in heat transfer coefficient due the coolant injection was found to be significantly smaller for the high mainstream turbulence case compared to the low mainstream turbulence case. This was particularly important when evaluating the overall performance of this film cooling hole configuration, since the much smaller relative increase in heat transfer coefficient resulted in good performance in terms of net heat flux reduction.

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An experimental and computational investigation was conducted on the film cooling adiabatic effectiveness of a flat plate with full coverage film cooling. The full coverage film cooling array was comprised of ten rows of coolant holes, arranged in a staggered pattern, with short, L/D = 1, normal coolant holes. A single row of coolant holes was also examined to determine the accuracy of a superposition prediction of the full coverage adiabatic effectiveness performance. Large density coolant jets and high mainstream turbulence conditions were utilized to simulate realistic engine conditions. High-resolution adiabatic effectiveness measurements were obtained using infrared imaging techniques and a large-scale flat plate model. Optimum adiabatic effectiveness was found to occur for a blowing ratio of M = 0.65. At this blowing ratio separation of the coolant jet immediately downstream of the hole was observed. For M = 0.65, the high mainstream turbulence decreased the spatially averaged effectiveness level by 12 percent. The high mainstream turbulence produced a larger effect for lower blowing ratios. The superposition model based on single row effectiveness results over-predicted the full coverage effectiveness levels.