Gas turbine airfoil with shaped trailing edge coolant ejection holes

1. A turbine blade or vane comprising:

at least one internal radial channel for the circulation of cooling medium bordered on a pressure side by a pressure side wall and on a suction side by a suction side wall joined at a upstream side at a leading edge and at and downstream side at the trailing edge;

at least one exit hole through at least one of the pressure side wall or the suction side wall for blowing out of cooling medium from the internal radial channel to a medium surrounding the blade or vane;

at least one trailing edge exit hole along the trailing edge and having a surfacial exit opening disposed at the pressure side of the trailing edge; and

at least one radial leading-edge cooling passage disposed in proximity to the leading edge, at least one intermediate cooling passage and at least one trailing edge cooling passage disposed in proximity to the trailing edge, the trailing edge exit hole being supplied by the trailing edge cooling passage;

wherein at the trailing edge, the pressure side wall of the blade or vane includes a step recessed towards the suction side, the at least one trailing edge exit hole being at least partly open towards the surrounding medium in a reqion of the step, and

wherein the trailing edge exit hole is supplied by cooling medium via a bore which only partly opens in a radially extending leading-edge surface of the step and which at least partly channels through the bottom surface of the step forming scarfed holes.

2. The turbine blade or vane recited in claim 1 , wherein the trailing edge exit hole is configured to blow out cooling air to the medium surrounding the blade or vane under an angle with respect to the pressure side wall surface at a blowout point in a range of 5-45°.

3. The turbine blade or vane recited in claim 1 , wherein an angle with respect to the pressure side wall surface is in a range of 5-30°.

4. The turbine blade or vane recited in claim 1 , wherein the trailing edge side of the surfacial exit opening of the trailing edge exit hole is not more than 50 mm upstream of the trailing edge along the pressure side wall surface.

5. The turbine blade or vane recited in claim 1 , wherein at least two trailing edge exit holes are disposed along the trailing edge and along a radial direction that are supplied via individual cooling medium bores connecting the trailing edge exit holes to the internal radial channel.

6. The turbine blade or vane recited in claim 5 , wherein at least one of the cooling medium bores or trailing edge exit holes is inclined with respect to an axial direction of a machine with a positive or negative angle in a range of 0-50°.

7. The turbine blade or vane recited in claim 1 , wherein the trailing edge exit hole includes a bore connecting the internal radial channel with the medium surrounding the blade or vane, the bore including, on a side connecting to the internal radial channel, a circular cylindrical section, and on a side to the surface of the blade or vane, a widening section conically widening towards the surface of the blade or vane.

8. The turbine blade or vane recited in claim 7 , wherein a ratio of a length of the circular cylindrical section to a total length of the circular cylindrical section and the widening section is in the range of 0.2-0.7.

9. The turbine blade or vane recited in claim 1 , wherein the trailing edge exit hole includes a bore connecting the internal radial channel with the medium surrounding the blade or vane, a ratio of the length of the bore to a diameter of the bore being in a range of 5-50.

10. The turbine blade or vane recited in claim 1 , wherein at least the totality of the surfacial opening of the trailing edge exit hole is located in a radially extending leading-edge surface of the step.

11. The turbine blade or vane recited in claim 10 , wherein surfacial opening of the trailing edge exit hole is disposed at an angle in the range of 60-120° with respect to a radially extending bottom surface of the step.

12. The turbine blade or vane recited in claim 1 , wherein the trailing edge exit hole is supplied by cooling medium via a bore with a diameter (d) which fully opens in a radially extending leading-edge surface of the step and which is distanced from the bottom surface of the step by a first distance (S 1 ) in a range of S 1 /d=1.0-1.8, and distanced from the pressure side wall surface by a second distance (S 2 ) in a range of S 2 /d=0.1-0.3.

13. The turbine blade or vane recited in claim 5 , wherein a cross-section of the bore, in one of the wall structure of the blade or vane or at the surfacial opening line, is circular, oval, elliptical or racetrack shaped.

14. The turbine blade or vane recited in claim 1 , wherein the blade or vane is at least partly based on metal.

15. The turbine blade or vane recited in claim 1 , wherein the blade or vane is a rotating or stationary turbine aerofoil.

16. A turbine including a turbine blade comprising:

at least one internal radial channel for the circulation of cooling medium bordered on a pressure side by a pressure side wall and on a suction side by a suction side wall joined at a upstream side at a leading edge and at and downstream side at the trailing edge;

at least one exit hole through at least one of the pressure side wall or the suction side wall for blowing out of cooling medium from the internal radial channel to a medium surrounding the blade or vane;

at least one trailing edge exit hole along the trailing edge and having a surfacial exit opening disposed at the pressure side of the trailing edge; and

at least one radial leading-edge cooling passage disposed in proximity to the leading edge, at least one intermediate cooling passage and at least one trailing edge cooling passage disposed in proximity to the trailing edge, the trailing edge exit hole being supplied by the trailing edge cooling passage;

wherein at the trailing edge, the pressure side wall of the blade or vane includes a step recessed towards the suction side, the at least one trailing edge exit hole being at least partly open towards the surrounding medium in a region of the step, and

wherein the trailing edge exit hole is supplied by cooling medium via a bore which only partly opens in a radially extending leading-edge surface of the step and which at least partly channels through the bottom surface of the step forming scarfed holes.

17. The turbine recited in claim 16 , wherein the turbine is a gas turbine.