Combustion turbine with airfoil having multi-section diffusion cooling holes and methods of making same
View Patent ↗A combustion turbine 20 includes a housing 22 and a plurality of airfoils 40 radially and rotatably positioned within the housing. At least one interior cooling passageway 50 extends within the airfoil 40 , and a plurality of diffusion holes 52 extend therefrom to a suction surface 46 and/or a pressure surface 48 of the airfoil. Each diffusion hole 52 has a proximal section 54 having a generally constant cross-sectional shape, and at least one other outwardly tapered section connected to the proximal section and defining 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.
1. 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.
2. An airfoil according to claim 1 wherein the cross-sectional shape of the medial tapered section tapers outwardly from the proximal section along the downstream gas flow direction, radially inward direction and radially outward direction at respective angles in a range of about 3° to about 7°.
3. An airfoil according to claim 1 wherein the cross-sectional shape of the distal tapered section tapers outwardly from the medial tapered section along the downstream gas flow direction, and radially inward direction at respective angles in a range of about 7° to about 10°.
4. An airfoil according to claim 1 wherein the cross-sectional shape of the distal tapered section defines distinct angular transitions with the medial tapered section.
5. An airfoil according to claim 1 wherein the proximal section has a generally circular cross-sectional shape.
6. An airfoil according to claim 1 wherein the proximal section defines an axis inclined at an angle in a range of about 45° to about 55° relative to the downstream gas flow direction.
7. A combustion turbine comprising:
a housing and a plurality of airfoils being radially positioned within said housing and being rotatable based upon a gas flow thereover;
each airfoil having
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.
8. A combustion turbine according to claim 1 wherein the cross-sectional shape of the medial tapered section tapers outwardly from the proximal section along the downstream gas flow direction, radially inward direction and radially outward direction at respective angles in a range of about 3° to about 7°.
9. A combustion turbine according to claim 1 wherein the cross-sectional shape of the distal tapered section tapers outwardly from the medial tapered section along the downstream gas flow direction, and radially inward direction at respective angles in a range of about 7° to about 10°.
10. A combustion turbine according to claim 1 wherein the cross-sectional shape of the distal tapered section defines distinct angular transitions with the medial tapered section.
11. A combustion turbine according to claim 1 wherein the proximal section has a generally circular cross-sectional shape.
12. A combustion turbine according to claim 1 wherein the proximal section defines an axis inclined at an angle in a range of about 45° to about 55° relative to the downstream gas flow direction.
13. A method for making diffusion holes in an airfoil for a combustion turbine, the airfoil to be radially positioned within a housing and being rotatable based upon gas flow thereover, the airfoil having a leading edge surface, a trailing edge surface, 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, the method comprising:
forming a plurality of diffusion holes to extend 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.