Influence of mainstream turbulence on heat transfer coefficients from a gas turbine blade
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The influence of mainstream turbulence on surface heat transfer coefficients of a gas turbine blade was studied. The experiments were performed with a five -blade linear cascade in a low speed wind tunnel facility. The mainstream Reynolds numbers were 100,000, 200, 000, and 300,000 based on the cascade inlet velocity and blade chord length. The grid-generated turbulence intensities at the cascade inlet were varied between 2.8 and 17%. A hot wire anemometer system was used to measure turbulence intensities, mean and time dependent velocities at the cascade inlet, outlet, and several locations in the middle of the flow passage. A thin-foil thermocouple instrumental blade was used to determine the surface heat transfer coefficients. The results show that the mainstream turbulence promotes earlier and longer boundary layer transition, causes higher heat transfer coefficients on the suction surface, and significantly enhances the heat transfer coefficient on the pressure surface. The onset of transition on the suction surface boundary layer moves forward with increased mainstream turbulence intensity and Reynolds number. The heat transfer coefficient augmentations and peak values on the suction and pressure surfaces are affected by the mainstream turbulence and Reynolds number.
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