Patent ID: 6918742

Claim:
An airfoil for a combustion turbine comprising: a leading edge surface, a trailing edge surface, and suction and pressure surfaces extending between the leading and trailing edge surfaces, the pressure surface having a radially outward edge; and at least one interior cooling passageway and a plurality of diffusion holes extending from the at least one interior cooling passageway to at least one of the suction and pressure surfaces; each diffusion hole being defined by a proximal section having a generally constant cross-sectional shape, and an outwardly tapered distal section connected thereto to define a greater taper in a downstream gas flow direction than an upstream gas flow direction and a greater taper in a radially inward direction than a radially outward direction, and a medial tapered section having a cross-sectional shape tapering more along the downstream gas flow direction than the upstream gas flow direction with no taper in the upstream gas flow direction, and a smaller tapering angle at the medial tapered section than the distal tapered section and a distinct angular transition between the proximal and medial sections, wherein the radially outward edge of the pressure surface is at an angle to the direction of downstream gas flow from each diffusion hole to permit cooling gas to exit a diffusion hole in a direction more consistent with flow tendency of gas.