Cooled turbine guide vane or blade for a turbomachine

Abstract

A turbine airfoil has a suction side wall and a pressure side wall of an airfoil cavity, through which a cooling fluid flows for cooling of the side walls. The suction side wall has one or more protrusions extending therefrom into the airfoil cavity. The protrusions are arranged such that: a number of the one or more protrusions on the suction side wall is higher than a number of protrusions on the pressure side wall; and/or a protrusion density on the suction side wall is higher than a protrusion density on the pressure side wall, and/or a total protrusion surface area on the suction side wall is larger than a total protrusion surface area on the pressure side wall, so that the heat transfer from the suction side wall to the cooling fluid is higher compared to that of the pressure side wall during operation of the turbomachine.

Claims

1. A turbine airfoil for a turbomachine, the turbine airfoil comprising: a suction side wall and a pressure side wall bordering an airfoil cavity, which is adapted to be flowed through by a cooling fluid for cooling of the side walls, wherein the suction side wall comprises protrusions extending therefrom inside the airfoil cavity, wherein the protrusions are arranged such that: a number of the protrusions on the suction side wall is higher than a number of protrusions on the pressure side wall; and/or a protrusion density on the suction side wall is higher than a protrusion density on the pressure side wall, and/or a total protrusion surface area on the suction side wall is larger than a total protrusion surface area on the pressure side wall, so that the heat transfer from the suction side wall to the cooling fluid is higher compared to the heat transfer from the pressure side wall to the cooling fluid during operation of the turbomachine, and wherein the suction side wall and the pressure side wall each comprise film cooling holes and a respective diameter of the film cooling holes on the suction side wall is smaller than a respective diameter of the film cooling holes on the pressure side wall.

2. The turbine airfoil according to claim 1, wherein at least one of the protrusions extending from the suction side wall is a turbulator for the cooling fluid flow.

3. The turbine airfoil according to claim 1, wherein at least one of the protrusions extending from the suction side wall is a cone, a pyramid or a tetrahedron.

4. The turbine airfoil according to claim 1, wherein at least one of the protrusions extending from the suction side wall is an elongated rib.

5. The turbine airfoil according to claim 1, wherein at least one of the protrusions extending from the suction side wall extends from an interior surface of the suction side wall to the pressure side wall forming a pedestal around which the cooling fluid can flow.

6. The turbine airfoil according to claim 1, wherein at least one of the one or more protrusions is located adjacent to a trailing edge of the turbine airfoil.

7. The turbine airfoil according to claim 1, wherein the turbine airfoil comprises a trailing edge and at least one passage in the trailing edge, wherein the at least one passage is provided for outflow of the cooling fluid from the airfoil cavity.

8. The turbine airfoil according to claim 1, wherein the turbine airfoil is film cooled.

9. The turbine airfoil according to claim 1, wherein the film cooling holes are arranged such that: a number of the film cooling holes on the suction side wall is smaller than a number of film cooling holes on the pressure side wall, and/or a density of the film cooling holes on the suction side wall is smaller than a density of film cooling holes on the pressure side wall.

10. The turbine airfoil according to claim 1, wherein at least one of the protrusions extending from the suction side wall is an elongated rib with a triangular cross section.

11. The turbine airfoil according to claim 1, wherein the turbine airfoil comprises a trailing edge, and wherein at the trailing edge the suction side wall extends aft farther than the pressure side wall.

12. The turbine airfoil according to claim 1, wherein the turbine airfoil comprises a trailing edge and a leading edge, wherein the airfoil cavity is disposed immediately upstream of an exit passage through the trailing edge, and wherein a direction of flow of the cooling fluid through the airfoil cavity and out the exit passage is from the leading edge toward the trailing edge.

13. A turbine airfoil for a turbomachine, the turbine airfoil comprising: a leading edge, a trailing edge, and a suction side wall and a pressure side wall that define an airfoil cavity immediately upstream of an exit passage through the trailing edge, the turbine airfoil configured to pass a flow of cooling fluid through the airfoil cavity in a direction from the leading edge toward the trailing edge, wherein the suction side wall comprises suction-side protrusions extending therefrom into the flow of cooling fluid, wherein the pressure side wall comprises one or more pressure-side protrusions extending therefrom into the flow of cooling fluid, and wherein a protrusion density of the suction-side protrusions is higher than a protrusion density of the one or more pressure-side protrusions so that the heat transfer from the suction side wall to the flow of cooling fluid is higher compared to the heat transfer from the pressure side wall to the flow of cooling fluid during operation of the turbomachine, and suction side film cooling holes through the suction side wall and pressure side film cooling holes through the pressure side wall, wherein a respective diameter of the suction side film cooling holes is smaller than a respective diameter of the pressure side film cooling holes.

14. The turbine airfoil according to claim 13, wherein a number, a density, and the diameter, respectively, of the suction side film cooling holes is smaller than that of a number, a density, and the diameter, respectively, of the pressure side film cooling holes.

15. A turbine airfoil for a turbomachine, the turbine airfoil comprising: a leading edge, a trailing edge, and a suction side wall and a pressure side wall that define an airfoil cavity immediately upstream of an exit passage through the trailing edge, the turbine airfoil configured to pass a flow of cooling fluid through the airfoil cavity in a direction from the leading edge toward the trailing edge, wherein the suction side wall comprises protrusions extending therefrom into the flow of cooling fluid, wherein the pressure side wall comprises one or more protrusions extending therefrom into the flow of cooling fluid, wherein the protrusions are arranged such that: a number of the protrusions on the suction side wall is higher than a number of the one or more protrusions on the pressure side wall; and a protrusion density of the protrusions on the suction side wall is higher than a protrusion density of the one or more protrusions on the pressure side wall, and a total protrusion surface area of the protrusions on the suction side wall is larger than a total protrusion surface area of the one or more protrusions on the pressure side wall, so that the heat transfer from the suction side wall to the flow of cooling fluid is higher compared to the heat transfer from the pressure side wall to the flow of cooling fluid during operation of the turbomachine, the turbine airfoil further comprising film cooling holes arranged such that: a number of the film cooling holes on the suction side wall is smaller than a number of film cooling holes on the pressure side wall, and a density of the film cooling holes on the suction side wall is smaller than a density of film cooling holes on the pressure side wall, and a diameter of the film cooling holes on the suction side wall is smaller than a diameter of film cooling holes on the pressure side wall.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following the invention is explained on the basis of a preferred embodiment of the turbine blading with reference to the drawing. In the drawing the FIGURE shows a sectional view of the embodiment.

DETAILED DESCRIPTION OF INVENTION

(2) In the FIGURE, an embodiment of a turbine airfoil 1 of a turbomachine is shown. The turbine airfoil 1 can be a rotor blade as well as a guide vane. The turbine airfoil 1 comprises a suction side wall 2 and a pressure side wall 3 which border a cavity 4an airfoil cavity, a hollow space inside the airfoil 1inside the turbine airfoil 1. In the FIGURE, the trailing edge 11 of the turbine airfoil 1 and the area adjacent to the trailing edge 11 are shown. The width of the cavity 4 reduces towards the trailing edge 11.

(3) Each of the walls 2, 3 comprises an inner face 6 and an outer face 5. During the operation of the turbomachine a hot gas (not shown) flows in the flow channel 13 between two adjacent turbine airfoils along the walls 2, 3 with a main flow direction directed from the leading edge (not shown) to the trailing edge 11. In the cavity a cooling fluid 7 flows with a cooling fluid main flow direction 8 which is substantially parallel to the walls 2, 3 and oriented towards the trailing edge 11. At the trailing edge 11 the turbine airfoil 1 comprises a passage 12 via which the cooling fluid 7 discharges the cavity 4. At the trailing edge 11, the suction side wall 2 is more elongated than the pressure side wall 3, so that after discharging the cavity 4 the cooling fluid 7 flows along the inner face 6 of the suction side wall, providing a flow or film of cooling fluid. It is also possible that the suction side wall 2 and the pressure side wall 3 are the same length.

(4) The suction side wall 2 comprises two protrusions 9 extending therefrom inside the cavity 4. Possible is also that the suction side wall 2 comprises one protrusion 9 or a plurality of protrusions 9. The protrusions 9 have a conical shape with the base of the cone arranged on the inner face 6 of the suction side wall 2. With the protrusions 9 a large surface inside the turbine airfoil 1 with a small blockage for the cooling fluid 7 flow can be achieved. The shape of the cone is preferably such that the edge of the cone has such a large angle that a flow separation downstream of the cone, which would result in the formation of a recirculation zone, is avoided. Other shapes of the protrusions 9 are also possible, for example a truncated cone, with the larger base arranged on the suction side wall, a shape that would particularly prevent the flow separation.

(5) Also possible is that the protrusions 9 have such a shape that they function as turbulators. The turbulators have the effect that downstream of the cooling fluid 7 main flow direction 8, the cooling fluid 7 flow originating from the turbulators has increased turbulence. A cooling fluid 7 flow with enhanced turbulence cools the suction side wall 2 more efficiently by convective cooling than a cooling flow 7 along a smooth surface which may substantially form a film on the surface.

(6) Also shown in the FIGURE is a pedestal 10 with a cylindrical shape, which is arranged between both protrusions 9 and extends from the suction side wall 2 to the pressure side wall 3. The pedestal can also have an e.g. rectangular cross section. In another preferred embodiment, in order to have a higher heat transfer from the suction side wall 2 the pedestal 10 can be a truncated cone, with the larger base of the truncated cone arranged on the suction side wall 2 and the smaller base arranged on the pressure side wall 3. In a further preferred embodiment the pedestal 10 comprises a truncated cone, which is arranged with its larger base at the suction side wall 2 and at its smaller base a cylinder is arranged, which extends to the pressure side wall 3. The diameter of the pedestal 10 is chosen such that sufficient cooling fluid 7 for the convective cooling can be flown around the pedestal. It is preferred that the protrusions 9 and the pedestal 10 are arranged at gap, so that they are not in the flow shadow zone of each other. It is also preferred that the protrusions 9 and the pedestals 10 are arranged in a distance from the tip or hub, leading edge and trailing edge 11 of the airfoil 1, so that sufficient cooling air 7 can be provided for these areas.

(7) Possible is also a preferred embodiment, wherein the turbine airfoil 1 comprises a plurality of film cooling holes 14 in the walls 2, 3. Due to the protrusions 9 on the suction side wall 2 the distance between film cooling holes can be increased and the total flow of air reduced, compared to an airfoil 1 with the protrusions 9, whereby the contribution of the film cooling is smaller on the suction side wall 2. Hence, losses due to mixing of the hot gas and the cooling fluid 7 on the suction side wall 2 are reduced. Also possible is that sufficient cooling from inside the airfoil 1 is achieved due to the protrusions so that the film cooling can be completely eliminated.

(8) Although the invention is described in detail by the preferred embodiments, the invention is not constrained by the disclosed examples and other variations can be derived by the person skilled in the art, without leaving the extent of the protection of the invention.