Abstract: The film of cooling air adjacent the outer surface of the airfoil of a turbine of a gas turbine engine issuing from internally of the turbine subsequent to cooling is controlled by regulating the pressure ratio of the internal to external pressures by forming an internal chamber extending longitudinally in the turbine and having fixed orifices admitting cooling air therein bearing a predetermined relationship to the exit orifices forming the film of cooling air. By regulating this pressure ratio the diameter of the exit holes can be longer than heretofore designs for a given application so that they can be precast rather than drilled and can be arranged to give fuller coverage of films of cooling air on the outer surface of the airfoil.

Abstract: The wall of a hollow airfoil has a longitudinally extending slot in its external surface which is intersected, at its base, by a plurality of coolant passages in a longitudinally extending row. Each coolant passage has a metering portion at its inner end which communicates with a coolant compartment within the hollow airfoil. Each passage includes a pair of walls downstream of the metering portion which diverge from each other in the longitudinal direction and intersect with the base of the slot to form an outlet for the passage. The diverging walls of adjacent passages substantially meet each other at the base of the slot, wherein coolant fluid from the metering portions of the passages diffuses in the longitudinal direction as it flows toward and into the slot, filling the entire slot and forming a thin, continuous film of coolant downstream of and along the entire length of the slot over the external surface of the airfoil.