Gas turbine engine high lift airfoil cooling in stagnation zone

1. An airfoil for a gas turbine engine, comprising:

pressure and suction side walls joined to one another at leading and trailing edges and forming an exterior airfoil surface extending in a radial direction to a tip, wherein a chord-wise direction extends from the leading edge to the trailing edge, a stagnation line located on the pressure side wall aft of the leading edge, a cooling passage provided between the pressure and suction side walls, and forward-facing cooling holes provided adjacent to the stagnation line on the pressure side wall and oriented toward the leading edge, a first centerline of the forward-facing cooling holes are at a first acute angle relative to a first line tangent to the exterior airfoil surface at the first centerline, the first acute angle and the first line are arranged in a first plane that extends in the chord-wise direction;

a group of cooling holes clustered about the leading edge on both the pressure and suction side walls and distributed along a radial direction of the leading edge, the forward-facing cooling holes spaced aft of the group of cooling holes, wherein the forward-facing cooling holes are forward of the stagnation line and oriented toward the tip;

aft-facing cooling holes provided aft of the stagnation line on the pressure side wall and oriented toward the trailing edge, a second centerline of the aft-facing cooling holes are at a second acute angle relative to a second line tangent to the exterior airfoil surface at the second centerline, the second acute angle and the second line are arranged in a second plane that extends in the chord-wise direction, the first and second acute angles are adjacent to the stagnation line; and

wherein the airfoil has a Zweifel lift coefficient of greater than 1.1.

2. The airfoil according to claim 1 , wherein the forward-facing cooling holes extend from a midspan of the airfoil to the tip.

3. The airfoil according to claim 1 , wherein the aft-facing cooling holes are oriented toward the tip of the airfoil.

4. The airfoil according to claim 1 , wherein the stagnation line overlaps the leading edge.

5. The airfoil according to claim 1 , wherein the airfoil is a high lift airfoil.

6. The airfoil according to claim 1 , wherein the airfoil is a turbine blade.

7. The airfoil according to claim 1 , wherein the group of cooling holes are shower head cooling holes.

8. The airfoil according to claim 7 , wherein the shower head cooling holes include a cluster of three rows of holes extending in a radial direction, the three rows including a first row extending along the leading edge and second and third rows respectively arranged adjacent to and on opposing sides of the first row.

9. The airfoil according to claim 7 , wherein the shower head cooling holes provide generally circular exits provided on the exterior airfoil surface.

10. A gas turbine engine comprising:

a compressor section;

a combustor fluidly connected to the compressor section;

a turbine section fluidly connected to the combustor, the turbine section includes:

an array of turbine blades, each turbine blade includes an airfoil having leading and trailing edges joined by spaced apart pressure and suction sides to provide an exterior airfoil surface extending in a radial direction to a tip, wherein a chord-wise direction extends from the leading edge to the trailing edge, a stagnation line provided on the pressure side wall aft of the leading edge, a cooling passage provided between the pressure and suction side walls, and forward-facing cooling holes provided adjacent to the stagnation line on the pressure side wall and oriented toward the leading edge, a first centerline of the forward-facing cooling holes are at a first acute angle relative to a first line tangent to the exterior airfoil surface at the first centerline, the first acute angle and the first line are arranged in a first plane that extends in the chord-wise direction;

a group of cooling holes clustered about the leading edge on both the pressure and suction side walls and distributed along the radial direction, the forward-facing cooling holes spaced aft of the group of cooling holes, wherein the forward-facing cooling holes are forward of the stagnation line and oriented toward the tip;

aft-facing cooling holes provided aft of the stagnation line on the pressure side wall and oriented toward the trailing edge, a second centerline of the aft-facing cooling holes are at a second acute angle relative to a second line tangent to the exterior airfoil surface at the second centerline, the second acute angle and the second line are arranged in a second plane that extends in the chord-wise direction, the first and second acute angles are adjacent to the stagnation line; and

wherein the airfoil has a Zweifel lift coefficient of greater than 1.1.

11. The gas turbine engine according to claim 10 , wherein the forward-facing cooling holes extend from a midspan of the airfoil to the tip of the airfoil.

12. The gas turbine engine according to claim 10 , wherein the aft-facing cooling holes are oriented toward the tip of the airfoil.

13. The gas turbine engine according to claim 10 , wherein the stagnation line overlaps the leading edge.

14. The gas turbine engine according to claim 10 , wherein the group of cooling holes are shower head cooling holes.

15. The gas turbine engine according to claim 14 , wherein the shower head cooling holes include a cluster of three rows of holes extending in a radial direction, the three rows including a first row extending along the leading edge and second and third rows respectively arranged adjacent to and on opposing sides of the first row.

16. The gas turbine engine according to claim 14 , wherein the shower head cooling holes provide generally circular exits provided on the exterior airfoil surface.