Gas turbine combustion device

1. A gas turbine combustion device comprising:

a combustion chamber including a front plate; and

at least one burner connected to the front plate;

wherein the front plate comprises, spaced apart from one another, a front sheet and an impingement sheet, the front sheet and the impingement sheet including aligned holes receiving the at least one burner, and a piston ring between the front sheet and the impingement sheet to seal the holes;

wherein an axial length of a border of the front sheet hole, of the impingement sheet hole, or of both, is longer than a thickness of the corresponding front sheet, of the corresponding impingement sheet, or of both; and

wherein diameters of the holes of the front sheet and impingement sheet are each larger than a diameter of the burner such that during operation the front sheet and impingement sheet are contactable with the burner.

2. The combustion device as claimed in claim 1 , wherein the front sheet, the impingement sheet, or both comprise at least two different pieces, one of said at least two different pieces at least partially defining at least one of said holes.

3. The combustion device as claimed in claim 2 , wherein the at least two different pieces comprise a first piece defining the hole of the front sheet or the impingement sheet and a second piece defining a main portion of the front sheet or the impingement sheet, the first piece being welded to the second piece.

4. The combustion device as claimed in claim 3 , wherein the first piece and the second piece define the front sheet.

5. The combustion device as claimed in claim 4 , further comprising:

a heat resistant protective layer on a side of the front sheet facing an inside of the combustion chamber covering the weld between the first piece and the second piece.

6. The combustion device as claimed in claim 3 , wherein the border of the front sheet hole, of the impingement sheet hole, or of both comprises a wear resistant protective coating extending up to a side facing the piston ring.

7. The combustion device as claimed in claim 3 , wherein the first piece and the second piece comprise cooling through holes.

8. The combustion device as claimed in claim 7 , wherein the first piece cooling through holes are inclined with respect to a hole axis.

9. The combustion device as claimed in claim 8 , wherein said first piece cooling through holes converge towards the inside of the combustion chamber.

10. The combustion device as claimed in claim 1 , wherein the piston ring has an inner diameter smaller than an inner diameter of the front sheet hole, and the inner diameter of the front sheet hole is smaller than an inner diameter of the impingement sheet hole.

11. The combustion device as claimed in claim 1 , wherein an axial length of the border of the hole of the front sheet, of the impingement sheet, or of both is parallel to an axis perpendicular to the corresponding sheet.

12. The combustion device as claimed in claim 1 , wherein the front plate comprises an annular structure which comprises a plurality of sectors joined together.

13. The combustion device as claimed in claim 12 , wherein each of the sectors has a substantially trapezoidal shape.

14. The combustion device as claimed in claim 2 , wherein the at least two different pieces define the border of the hole of the front sheet, of the impingement sheet, or of both such that the axial length of the border is longer than the thickness of the corresponding sheet.

15. The combustion device as claimed in claim 1 , wherein the impingement sheet has through holes in addition to said hole.

16. The combustion device as claimed in claim 1 , wherein the aligned holes of the front sheet and the impingement sheet face a rectilinear section of the burner.