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.
A Typical Turbine Blade with Film Cooling Holes
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