Date of Award

3-2020

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Marc D. Polanka, PhD

Abstract

With technological advancements allowing higher turbine temperatures, film cooling continues to be an important research area. The Film Cooling Rig (FCR) was fitted with a turbulence generator to vary freestream turbulence intensity and length scale, enabling the effects of high freestream turbulence on overall effectiveness to be studied. A cylindrical hole and laidback fan-shaped hole were investigated over a range of Advective Capacity Ratio (ACR) for freestream turbulence intensities of 2%, 10%, and 15%. For a given ACR, increasing the turbulence intensity resulted in lower overall effectiveness values due to the larger heat transfer coefficient that comes from turbulent ow. As expected, the laidback fan-shaped hole resulted in increased overall effectiveness values compared to the cylindrical hole due. This was the result of the laidback fan-shaped hole's ability to keep the coolant jet closer to the surface. Increasing Reynolds number also decreased the overall effectiveness due to the increased external heat transfer coefficient. A new equation for overall effectiveness predicted the change in overall effectiveness from increasing parameters such as the external and internal heat transfer coefficients. For a given ACR, increasing the internal heat transfer coefficient resulted in increased overall effectiveness due to the lower temperatures in the coolant channel drawing heat from the external surface. Increasing the coolant ow rate in the channel, and decreasing the temperature in the coolant channel, resulted in lower airfoil temperatures upstream and downstream of the channel due to an increase in conductive heat ux through the airfoil. Conduction in the rig caused the temperature of the coolant to dramatically increase within a short distance. This implies that in a turbine engine, the density of the coolant entering the cooling holes is significantly lower than the density in the coolant line.

AFIT Designator

AFIT-ENY-MS-20-M-270

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