Patent ID: 7300252

Claim:
Gas turbine airfoil with a pressure sidewall and a suction sidewall, extending from a root to a tip and from a leading edge to a trailing edge and comprising several cooling passages between the pressure sidewall and the suction sidewall for cooling air to pass through and cool the airfoil from within, and where one or several of the cooling passages extend along the leading edge of the airfoil and several film cooling holes extend from the internal cooling passages along the leading edge to the outer surface of the leading edge; wherein the film cooling holes extending through the leading edge of the airfoil each have a sidewall that is diffused in the direction of the tip of the airfoil at least over a part of the length of the film cooling hole and that the film cooling holes each have a curved flare at the outer surface of the leading edge where the flare is directed toward the suction sidewall, or toward the pressure sidewall, or toward both the pressure sidewall and the suction sidewall of the airfoil; and wherein the film cooling holes each comprise a first portion and a second portion where the first portion has a cylindrical shape and extends from the internal cooling passage along the leading edge of the airfoil partially into the leading edge and the second portion extends from the first portion to the outer surface of the leading edge, and where the second portion has a sidewall closest to the tip of the airfoil that is diffused in the direction of the tip; wherein the sidewall of the film cooling hole diffused toward the tip of the airfoil forms a diffusion angle with the film cooling hole axis that is in the range of 3 to 7° and the axis of the film cooling holes form an angle with the outer surface of the leading edge that is in the range of 25° to 45°.