Blade for a gas turbine and method of cooling the blade

1. A blade with an airfoil profile for a gas turbine, comprising:

at least one direct cooling fluid inlet arranged at a bottom part of the blade, the bottom part of the blade being fixed to a rotor shaft of the gas turbine;

at least two opposite first and second walls enclosing an inner part of the blade and forming a plurality of cooling channels, the airfoil profile extending from the bottom part of the blade to a top part of the blade; and

at least a first and a second set of ribs respectively arranged on the at least two opposite first and second walls, said at least the first and the second set of ribs being located at an end of the cooling channels, ribs within each first and second set of ribs being arranged in parallel to each other and along one side of the airfoil profile of the blade, and said at least the first and the second set of ribs extending from a respective wall of the at least two opposite first and second walls into the inner part of the blade;

wherein the ribs within the first set of ribs on the first wall are superimposed over the ribs of the second set of ribs on another second wall;

wherein cooling fluid channels are formed in-between the ribs of the first set of ribs and are also formed in-between the ribs of the second set of ribs;

wherein an orientation of the ribs of the first set of ribs is different than an orientation of ribs of the second set of ribs; and

wherein a cross-section of the cooling fluid channels in-between neighboring ribs of the first set of ribs and a cross-section of the cooling fluid channels in-between neighboring ribs of the second set of ribs is smaller at a side oriented towards the bottom part of the blade in comparison to the side at the top part of the blade.

2. The blade according to claim 1 , wherein the bottom part of the blade comprises means to affix the blade to a rotor in a longitudinal direction of the airfoil profile perpendicular to a rotor axis of the gas turbine.

3. The blade according to claim 2 , further comprising:

fluid channels for flow of a cooling fluid channel formed in-between neighboring ribs within said at least the first and second set of ribs;

wherein a fluid flow direction of channels formed by the first set of ribs of said at least the first and the second set of ribs is in a direction opposite from the fluid flow direction of channels formed by a second set of ribs of said at least the first and set of ribs at an axis which extends parallel to the rotor axis.

4. The blade according to claim 2 , wherein the cross-section of the cooling fluid channels in-between ribs in said at least the first and the second set of ribs continuously increases along a perpendicular direction to the rotor axis from the bottom of the blade to the top part of the blade, in comparison to neighboring cooling fluid channels in said at least the first and the second set of ribs.

5. The blade according to claim 2 , wherein the cross-section of the cooling fluid channels in-between the ribs in said at least the first and the second set of ribs increases along a perpendicular direction to the rotor axis from the bottom to the top part of the blade by at least two values.

6. The blade according to claim 5 , wherein the at least two values is exactly two values consisting of a value at the side towards the bottom part of the blade and a value at the side towards the top part of the blade.

7. The blade according to claim 1 , wherein the cross-section in-between the ribs in said at least the first and the set of ribs at the side towards the bottom part of the blade is 1.5 mm and the cross-section in-between the ribs in said at least the first and the second set of ribs at the side at the top part of the blade is 2 mm.

8. The blade according to claim 1 , wherein said at least the first and the second set of ribs is arranged adjacent an outlet of cooling fluid of the blade.

9. The blade according to claim 8 , wherein the cooling fluid of the blade comprises one of air, oil a carbon hydride substance, water, nitrogen and oxygen.

10. The blade according to claim 2 , wherein the means are fixable to the rotor shaft via clamping or welding.

11. The blade according claim 1 , wherein the ribs within the first set of ribs are arranged with an angle to a rotor axis of the rotor shaft of 45 degrees or less, and the ribs within the second set of ribs are arranged with an angle to the rotor axis of the rotor shaft of −45 degrees or less; and wherein an angel between superimposed ribs of said at least the first and the second set of ribs and an angle of corresponding cooling fluid channels is in a range between 10 and 80 degrees.

12. The blade according claim 1 , wherein the ribs of the first set of ribs are arranged with an angle to a rotor axis of the rotor shaft of 20 degrees, and the ribs of the second set of ribs are arranged with an angle to the rotor axis of the rotor shaft of −20 degrees.

13. The blade according to claim 1 , wherein the cross-section of the cooling fluid channels formed by the first set of ribs and the cross-section of the cooling channels formed by the second set of ribs increases along a perpendicular direction to the rotor axis of the rotor shaft from the bottom part to the top part of the blade, wherein a value of the cross-section of the cooling fluid channels at the side oriented towards the bottom part is smaller than the value of the cross-section of the cooling fluid channels at the side towards the top part of the blade.

14. A gas turbine comprising a rotor with a rotor shaft and at least one blade as claimed in claim 1 .

15. The gas turbine according to claim 14 , wherein a bottom part of the at least one blade comprises means for affixing the at least one blade to the rotor shaft via clamping or welding.