What is Film Cooling?

Over the past fifty years, aircraft and power generation gas turbine designers have endeavored to increase the cumbustor exit and high-pressure turbine stage inlet temperatures. With higher combustor exit temperatures, improved efficiency and reduced fuel consumption can be achieved. Similarly, in aircraft application, the higher temperatures lead to increased thrust. Unfortunately, these higher temperatures have jeopardized the integrity of the high-pressure turbine components and specifically the turbine blades. Modern turbine stage inlet temperatures exceed the melting point temperatures of turbine blade materials. To combat and avert failure of turbine blades in gas turbine engines resulting from these excessive operating temperatures, film cooling has been incorporated into blade designs. In film cooling, cool air is bled from the compressor stage, ducted to the internal chambers of the turbine blades, and discharged through small holes in the blade walls. This air provides a thin, cool, insulating blanket along the external surface of the turbine blade.
Typical Turbine Blade
A Typical Turbine Blade with Film Cooling Holes

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