Trailing edge ejection cooling

1. An aerofoil comprising:

a leading edge and a trailing edge, the leading edge and the trailing edge connected by a pressure surface side and a suction surface side, and

one or more cavities bounded by at least one of the pressure surface side or the suction surface side and arranged, in use, to receive coolant from a coolant source, wherein:

the trailing edge has an apogee where the pressure surface side and the suction surface side meet,

the apogee has a thickness between the pressure surface side and the suction surface side,

a row of holes, orthogonal to the apogee, is provided with the centres of the holes arranged closer to one of a pressure surface side or a suction surface side relative to a centreline of the apogee,

the holes are in fluid communication with one or more of the cavities,

a part of each of the outlets to the holes is in the apogee such that a thickness of the apogee changes from a first end of the trailing edge to a second end of the trailing edge opposite the first end, and

a remainder of each of the outlets is in an adjacent part of the one of the pressure surface side or the suction surface side.

2. The aerofoil as claimed in claim 1 , wherein the row of holes extends along the entire apogee.

3. The aerofoil as claimed in claim 1 , wherein the row comprises equally spaced holes.

4. The aerofoil as claimed in claim 1 , wherein the row comprises unequally spaced holes.

5. The aerofoil as claimed in claim 1 , wherein the holes of the row are grouped with larger spaces between grouped holes.

6. The aerofoil as claimed in claim 1 , wherein the holes have a diameter of from 0.3 to 0.6 mm.

7. The aerofoil as claimed in claim 1 , wherein the thickness of the apogee is from 0.2 to 0.5 mm.

8. The aerofoil as claimed in claim 1 , wherein the cross sectional shape of the holes is selected from; circular, racetrack, elliptical or rectangular.

9. The aerofoil as claimed in claim 1 , wherein one or more holes are fanned along a centreline of the hole.

10. A method for manufacturing an aerofoil comprising:

manufacturing a blade body having a leading edge and a trailing edge, pressure surface side and a suction surface side and a cavity bounded by at least one of the pressure surface side or the suction surface side and the trailing edge;

in an apogee of the trailing edge, the apogee having a thickness between the pressure surface side and the suction surface side, drilling holes having their centres arranged to the pressure surface side or the suction surface side of a centreline of the apogee, the holes extending orthogonally to the apogee and into the cavity;

after drilling the holes, machine the trailing edge on the pressure surface side or the suction surface side so as to thin the apogee on the side to which the holes are drilled whilst retaining a part of the outlet of the holes in the apogee such that a thickness of the apogee changes from a first end of the trailing edge to a second end of the trailing edge opposite the first end.

11. The method as claimed in claim 10 , wherein the step of drilling the holes involves EDM.

12. The method as claimed in claim 10 , wherein the step of drilling involves a method selected from; laser drilling, STEM drilling or manual drilling.

13. The method as claimed in claim 10 , wherein the step of machining involves an adaptive machining process.

14. The method as claimed in claim 10 , further comprising performing a surface finishing operation to the machined surface.

15. The method as claimed in claim 10 , wherein the step of machining the trailing edge results in an the thickness of the apogee being from 0.2 to 0.5 mm.

16. The method as claimed in claim 10 , wherein the holes are drilled with a diameter of from 0.3 to 0.6 mm.