Method of repairing a gas turbine engine blade tip

Abstract

A method for repairing a blade of a gas turbine plant; the blade comprises an airfoil extending along a spanwise direction from a base to a tip; the tip is provided with a tip wall and an edge following at least partially a cross-sectional profile of the tip; the tip wall is provided with at least one first casting opening and the outer wall is provided with at least one first service opening; the first casting opening and the first service opening are closed by a first closing element; the method comprises the steps of: removing at least one first portion of the edge in the vicinity of the first casting opening and the first service opening; removing at least one first portion of the tip wall comprising the at least one first casting opening and at least one portion of the outer wall comprising the at least one first service opening; rebuilding the at least one first portion of the outer wall removed without the at least one first casting opening; rebuilding the at least one first portion of the tip wall removed without the at least one first casting opening; rebuilding the at least one first portion of the edge removed.

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to European Patent Application No. 20425023.7, filed on July 6, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to a method for repairing the tips of blades in a gas turbine device. Background Technology

[0004] As is well known, gas turbine power generation equipment includes a compressor, a burner, and a turbine.

[0005] Specifically, the compressor includes an inlet for supplying air and multiple rotating blades for compressing the air passing through it. The compressed air leaving the compressor flows into the booster chamber (i.e., the closed volume defined by the outer casing) and from there enters the combustion chamber.

[0006] Inside the combustor, compressed air is mixed with at least one type of fuel and burned. The resulting hot gas leaves the combustion chamber and expands in the turbine. In the turbine, the expansion of the hot gas causes rotating blades connected to the rotor to move, thereby doing work.

[0007] Both compressors and turbines include multiple stator assemblies that are axially inserted between rotor assemblies.

[0008] Each rotor assembly includes a rotor disk that rotates about a main axis and multiple blades supported by the rotor disk.

[0009] During the operation of the power generation equipment, the turbine blades are continuously exposed to the hot gas flow from the combustor.

[0010] The tip region of the blades is particularly exposed to hot gases. In fact, hot gas leakage typically occurs at the blade tips.

[0011] To reduce the leakage, the tip of the blade is provided with an edge that is shaped to create a recessed tip, also known as a sounder tip.

[0012] By using the tip of the sounder, the gap between the tip and the housing is reduced, thereby avoiding the risk of catastrophic failure caused by the tip rubbing against the housing during turbine operation.

[0013] Despite the reduced leakage flow, the tip region of the blades remains under high stress.

[0014] To provide an internal cooling path, openings are also arranged in the top region, which are unavoidably created during the casting process. In fact, these casting openings are necessary to support the ceramic core during the casting process. These casting openings remain even after the ceramic core is removed via chemical leaching / etching.

[0015] The casting opening is typically closed by a brazed closure element, which is often referred to as a "mailbox".

[0016] During use, these brazed closure elements are subjected to repeated stress and are severely damaged by TMF (thermomechanical fatigue) cracks and oxidation.

[0017] As a result, after a period of use, these brazed closure elements covering the openings were severely worn out.

[0018] If the brazed closure element is damaged, the blade cooling will no longer be efficient because the cooling fluid can flow through the casting opening.

[0019] During maintenance operations, known methods for repairing blade tips are employed. However, these techniques include restoring the original design by replacing the damaged closure element (mailbox) with a new one. However, these techniques have a high failure rate. Summary of the Invention

[0020] Therefore, the object of the present invention is to provide a method for repairing blade tips that is reliable, simple, economical and fast.

[0021] According to these objectives, the present invention relates to a method for repairing a blade of a gas turbine device; the blade includes an airfoil extending from a base to a tip along the spanwise direction; the airfoil includes an outer wall defining a leading edge, a trailing edge, a pressure side, and a suction side; the airfoil encloses at least one cooling duct extending along the spanwise direction and supplied with cooling fluid in use; the tip is provided with a tip wall and an edge that at least partially follows the profile of the tip cross-section; the tip wall is provided with at least one first casting opening, and the outer wall is provided with at least one first maintenance opening, the first maintenance opening being arranged adjacent to a corresponding first casting opening; the first casting opening and the first maintenance opening are closed using a first closure element;

[0022] The method includes the following steps

[0023] • Remove at least one first portion of the edge near the first casting opening and the first maintenance opening;

[0024] • Remove at least one first portion of the top wall, including at least one first casting opening, and at least one portion of the outer wall, including at least one first maintenance opening;

[0025] • Reconstruction of at least one first section of the outer wall that was removed without at least one first maintenance opening;

[0026] • Reconstruct at least one first portion of the top wall that was removed and does not have at least one first casting opening;

[0027] • Reconstruct at least one of the first parts of the edge that was removed. Attached Figure Description

[0028] The invention will now be described with reference to the accompanying drawings, which illustrate non-limiting embodiments of the invention, wherein:

[0029] - Figure 1 This is a schematic representation of a gas turbine device including blades to be repaired according to the method of the present invention, wherein parts are removed for clarity and a partial cross-section is shown;

[0030] - Figure 2 This is a schematic perspective view of a blade to be repaired according to the method of the present invention, wherein some parts have been removed for clarity;

[0031] - Figure 3 This is a schematic perspective view of the first detail of the blade to be repaired according to the method of the present invention, wherein parts have been removed for clarity;

[0032] - Figure 4-18 This is a schematic perspective view of the first details of the blade being repaired during different steps of the method according to the invention, wherein portions are removed for clarity. Detailed Implementation

[0033] exist Figure 1 In the figure, reference numeral 1 indicates a gas turbine device for electricity production, which includes a compressor 3, a burner 4, a gas turbine 5, and a generator 7. The generator converts the mechanical power supplied by the turbine 5 into electrical power that will be supplied to the power grid 8, which is connected to the generator 7 via a switch 9.

[0034] The variant not shown provides a device 1 belonging to the combined cycle type, and includes a steam turbine in addition to the gas turbine 5 and the generator 7.

[0035] The gas turbine 5 extends along the longitudinal axis A and is provided with a shaft 10 (also extending along axis A), to which the compressor 3 and generator 7 are also connected.

[0036] The gas turbine 5 includes an expansion passage 12 in which hot gas working fluid from the combustor 4 flows in direction D.

[0037] The expansion channel 12 has a cross section that increases radially along axis A in direction D.

[0038] In the expansion channel 12, multiple stages 13 are arranged at intervals along the longitudinal axis A. Each stage 13 includes rows of fixed blades and rows of rotating blades. Figure 1 (Not shown in the image). Each row includes circumferentially spaced blades extending radially outward from the corresponding support disc.

[0039] exist Figure 2 The image shows the rotating blades 15 of stage 13 of the gas turbine 5.

[0040] The blade 15 includes a root 17, an airfoil 18, and a platform 20.

[0041] The root 17 is configured to be connected to a support disc (not shown in the figures) of the gas turbine 5. Specifically, the disc has a plurality of axial supports that are circumferentially spaced and engaged by the respective roots 17 of the rotating blades 15.

[0042] The airfoil 18 extends from the root 17 along the wingspan direction S and has a base 21 connected to the root 17 and a top 22 opposite to the base 21 along the wingspan direction S.

[0043] In use, when the blade 15 is connected to the support disk, the span direction S is arranged substantially radially relative to the axis A of the gas turbine 5.

[0044] The airfoil 18 is fully housed in the expansion channel 12 and defines the aerodynamic profile of the rotating blade 15.

[0045] The airfoil 18 includes an outer wall 23, which externally defines a concave pressure side 24, a convex suction side 25, a leading edge 27, and a trailing edge 28.

[0046] In use, the pressure side 24 and the suction side 25 extend axially between the leading edge 27 and the trailing edge 28, and extend radially between the base 21 and the tip 22.

[0047] In use, the leading edge 27 is arranged upstream of the trailing edge 28 along the direction D of the hot working fluid in the expansion channel 12.

[0048] Platform 20 is positioned between root 17 and airfoil 18.

[0049] Reference Figure 3 The blade 15 includes the edge 29 at the tip 22.

[0050] Edge 29 protrudes from top 22 and follows the top cross-sectional profile. The term "cross-sectional profile" refers to the profile of airfoil 18 obtained by intersecting airfoil 18 with a plane perpendicular to the wingspan direction S at top 22.

[0051] In this way, edge 29 defines the top of the recess, also known as the "sounder top".

[0052] Specifically, edge 29 defines a top cavity 31 with a bottom defined by top wall 32, thereby defining an outer top surface 33.

[0053] Preferably, the edge 29 and the top 22 are integrally formed.

[0054] Reference Figure 2 and 3 The blade 15 is equipped with a cooling system 35.

[0055] The cooling system 35 includes a plurality of supply channels (not shown) formed in the root 17, and at least one cooling conduit 36 ​​formed in the airfoil 18 and supplied with cooling fluid from the supply channels in the root 17. Figure 3 (Middle part visible).

[0056] In the non-limiting examples disclosed and illustrated herein, the cooling system 35 includes at least three cooling conduits 36 (in... Figure 4 (More visible in the middle), one at the leading edge 27, one at the trailing edge 28, and one in the middle position between the leading edge 27 and the trailing edge 28.

[0057] The supply passage is supplied with cooling fluid from the coolant source 39. Preferably, the cooling fluid source 39 is part of the compressor 3.

[0058] exist Figure 1 The diagram shows an intake line 40 specifically designed to draw in cooling air from the compressor 3 and connect to the gas turbine 5.

[0059] The blade 15 is manufactured via a casting process. To obtain the cooling duct 36, this process requires a casting opening 42 on the top wall 32 (in... Figure 3 and 4 (Represented by dotted lines). These casting openings 42 are required during the casting process to support the ceramic core. These casting openings 42 remain after the ceramic core is removed by a chemical leaching / etching process.

[0060] In the non-limiting example disclosed and shown here, there are two casting openings 42: a "front" casting opening 42 is arranged at the leading edge 27, and a "rear" casting opening 42 is arranged in the middle position between the leading edge 27 and the trailing edge 28.

[0061] Reference Figure 3 The casting opening 42 is closed by a corresponding closing element 43 (indicated in gray), which is commonly referred to as a "mailbox".

[0062] In order to secure the closure element 43, at least one maintenance opening 44 is made substantially near the corresponding casting opening 42 on the suction side 25 and / or pressure side 24 at the top 22 during the manufacturing process.

[0063] In the non-limiting example disclosed and shown herein, there are two service openings 44: one on the suction side 25 and one on the pressure side 24.

[0064] Specifically, the maintenance opening 44 is obtained by electrical discharge machining and is shaped to allow the insertion of the corresponding closing element 43.

[0065] Each closing element 43 is shaped to simultaneously close the corresponding maintenance opening 44.

[0066] After insertion, the closing element 43 is brazed to reliably close the corresponding casting opening 42 and the corresponding maintenance opening 44.

[0067] As from Figure 4 and 5 As can be seen, the casting opening 42 and the maintenance opening 44 are connected to the corresponding cooling conduit 36.

[0068] The closing element 43 is preferably made of a material that is different from the material used on the outer wall 23 and has poorer resistance.

[0069] In other words, the blade 15 includes a front closing element 43 for closing the "front" casting opening 42 at the leading edge 27 and a rear closing element 43 for closing the "rear" casting opening 42 located in an intermediate position between the leading edge 27 and the trailing edge 28.

[0070] Figure 4-18 Different steps of a method for repairing the tip 22 of a blade 15 of a gas turbine device 1 according to the present invention are shown.

[0071] Figure 2 and 3 The blade 15 shown is an existing operating blade, which requires repair of its tip 22.

[0072] In fact, after a period of use, the closing element 43 of the closed casting opening 42 and maintenance opening 44 is severely worn.

[0073] If these closing elements 43 are damaged, the cooling of the blades 15 will no longer be efficient because the cooling fluid can flow through the casting opening 42 and / or the maintenance opening 44.

[0074] The method for repairing the tip of blade 15 according to the present invention can restore the blade so that it can be reused in turbine 5 in a new time period.

[0075] Therefore, the method for repairing the tip 22 of the blade 15 according to the present invention can be used to restore an existing blade 15, wherein at least one of the closing elements 43 is damaged or needs to be replaced due to impending breakage.

[0076] The method first involves removing at least one portion of edge 29.

[0077] The method includes removing at least a portion of edge 29 arranged substantially corresponding to the closure element 43 that requires intervention (e.g., is damaged or about to break). In other words, the method includes removing at least a portion of edge 29 arranged downstream of the closure element 43 requiring intervention (i.e., is damaged) along the spanwise direction S from the base 21 to the tip 22.

[0078] In the non-limiting examples disclosed and shown here, edge 29 is preferably completely removed, as... Figure 4 As clearly shown in the text.

[0079] The removal of edge 29 is preferably achieved by electrical discharge machining (EDM).

[0080] After removing at least a portion of edge 29, the method includes removing at least a portion 50 of outer wall 23 and at least a portion of top wall 32 near the closure element 43 requiring intervention. In the non-limiting example disclosed and shown herein, both the front closure element 43 and the rear closure element 43 require intervention.

[0081] Therefore, the method includes removing a portion 50a of the outer wall 23 and a portion 51a of the top wall 32 at the leading edge 27 (see...). Figure 5-8 And remove a portion 50b of the outer wall 23 and a portion 51b of the top wall 32 at the midpoint between the leading edge 27 and the trailing edge 28 (see...). Figure 9-12 ).

[0082] like Figure 5 and 6 As detailed herein, the removed portion 50a of the outer wall 23 has a height Ha (measured along the wingspan direction S), which is at least equal to the distance Da (measured along the wingspan direction S) between the outer surface 33 of the top wall 32 and the wall 52 of the maintenance opening 44 of the base 21 of the blade 15.

[0083] More preferably, such as Figure 7 As detailed in the document, the height Ha is less than the distance Di (measured along the span direction S) between the outer surface 33 of the top wall 32 and the inner wall 54 of the corresponding cooling duct 36.

[0084] In the non-limiting example disclosed and shown here, the height Ha is equal to the distance Da between the outer surface 33 of the top wall 32 and the wall 52 of the maintenance opening 44 closer to the base 21 of the blade 15.

[0085] Preferably, at the leading edge 27, the removed portion 50a of the outer wall 23 and the removed portion 51a of the top wall 32 extend along an arc C from the leading edge 27 to the end section 55. At the end section 55, the removed portion 50a of the outer wall 23 and the removed portion 51a of the top wall 32 are wedge-shaped.

[0086] The removal of portion 50a of the outer wall 23 and portion 51a of the top wall 32 is preferably achieved by electrical discharge machining (EDM).

[0087] like Figure 8 As shown, at the end of the removal of portion 50a of the outer wall 23 and portion 51a of the top wall 32, a recess 56 is present at the leading edge 27. The recess 56 has a chamfered portion 56a.

[0088] like Figure 9 and 10 As detailed herein, the height Hb (measured along the wingspan direction S) of the removed portion 50b of the outer wall 23 is at least equal to the distance Db (measured along the wingspan direction S) between the outer surface 33 of the top wall 32 and the wall 57 of the maintenance opening 44 of the base 21 of the blade 15.

[0089] More preferably, such as Figure 11 As detailed in the text, the height Hb is less than the distance Dii (measured along the spanwise direction S) between the outer surface 33 of the top wall 32 and the inner wall 54 of the corresponding cooling duct 36.

[0090] In the non-limiting example disclosed and shown here, the height Hb is equal to the distance Db between the top wall 32 and the wall 57 of the maintenance opening 44 closer to the base 21 of the blade 15.

[0091] Preferably, the removed portion 50b of the outer wall 23 and the removed portion 51b of the top wall 32 extend along arc C from a first section 58 contained between the leading edge 27 and the corresponding casting opening 45 to a second section 59 contained between the trailing edge 28 and the corresponding casting opening 42. At the first section 58 and the second section 59, the removed portion 50b of the outer wall 23 and the removed portion 51b of the top wall 32 are preferably wedge-shaped.

[0092] The removal of portion 50b of the outer wall 23 and portion 51b of the top wall 32 is preferably achieved by electrical discharge machining (EDM).

[0093] like Figure 12As shown, at the end of the removal of portion 50b of the outer wall 23 and portion 51b of the top wall 32, a recess 60 exists in the middle position between the leading edge 27 and the trailing edge 28. The recess 60 has two chamfered portions 61 and 62.

[0094] After removing portions 50a and / or 50b of the outer wall 23 and portions 51a and / or 51b of the top wall 32, the method includes utilizing additive manufacturing technology (see...). Figure 13 and 15 ) and the use of arc welding processes (see Figure 14 and 16 Reconstruct the outer wall 23 and the top wall 32.

[0095] In other words, the outer wall 23 is reconstructed using additive manufacturing technology, leaving an opening 64 at the leading edge and an opening 65 in the middle position between the leading edge 27 and the trailing edge 28. These openings 64 and 65 are substantially consistent with the casting opening 42, which is connected to the cooling conduit 36.

[0096] According to the method of the present invention, the openings 64 and 65 are closed by reconstructing the top wall 32 using an arc welding process.

[0097] Thus, at the end of the method, the casting opening 42 and the maintenance opening 44 no longer exist, and therefore the corresponding closing element 43 is no longer needed. Advantageously, this method is able to eliminate some of the weaknesses of the blade 15 (closing element 43).

[0098] Preferably, the outer wall 23 is reconstructed using a high-strength oxide material.

[0099] The preferred additive manufacturing technology is laser metal deposition.

[0100] The openings 64 and 65 of the top wall 32 are preferably closed using a tungsten inert gas welding (TIG) process.

[0101] exist Figure 17 In the middle, blade 15 is shown at the end of the reconstruction of outer wall 23 and top wall 32.

[0102] Finally, refer to Figure 18 The method includes reconstructing the edge 29, preferably by additive manufacturing technology, such as the same laser metal deposition process used for the outer wall 32 having the same material.

[0103] Finally, it is obvious that the methods described herein can be modified and varied without exceeding the scope of protection of the appended claims.

Claims

1. A method for repairing a blade (15) of a gas turbine device (1); said blade (15) comprising an airfoil (18) extending along a spanwise direction (S) from a base (21) to a tip (22); said airfoil (18) comprising an outer wall (23) defining a leading edge (27), a trailing edge (28), a pressure side (24), and a suction side (25); said airfoil (18) encapsulating at least one cooling duct (36) extending along said spanwise direction (S), and And is supplied with cooling fluid during use; the top end (22) is provided with a top end wall (32) and an edge (29) that at least partially follows the cross-sectional profile of the top end; the top end wall (32) is provided with at least one first casting opening (42), and the outer wall (23) is provided with at least one first maintenance opening (44), the first maintenance opening being arranged close to the corresponding first casting opening (42); the first casting opening (42) and the first maintenance opening (44) are closed by a first closing element (43); The method Includes the following steps • Remove at least one first portion of the edge (29) near the first casting opening (42) and the first maintenance opening (44); • Remove at least one first portion of the top wall (32) including the at least one first casting opening (42) and at least one first portion of the outer wall (23) including the at least one first maintenance opening (44); • Reconstruct the at least one first portion of the outer wall (23) that was removed and lacks the at least one first maintenance opening (44); • Reconstruct the at least one first portion of the top wall (32) that was removed and lacked the at least one first casting opening (42); • Reconstruct the removed first portion of the edge (29).

2. The method according to claim 1, wherein, The step of reconstructing the removed at least one first portion of the outer wall (23) is achieved using additive manufacturing technology.

3. The method according to claim 2, wherein the step of reconstructing the removed at least one first portion of the outer wall (23) is performed using a high-strength oxide material.

4. The method according to any one of claims 1 to 3, wherein the step of reconstructing the at least one first portion of the top wall (32) is performed using additive manufacturing technology and an arc welding process.

5. The method of claim 4, wherein the step of reconstructing the at least one first portion of the top wall (32) comprises using additive manufacturing techniques and using an arc welding process to close at least one opening (64; 65) left by the additive manufacturing.

6. The method according to claim 4, wherein the arc welding process is a tungsten inert gas (TIG) welding process.

7. The method according to any one of claims 1 to 3, wherein the step of reconstructing the removed at least one first portion of the edge (29) is performed using additive manufacturing technology.

8. The method according to any one of claims 2 to 3, wherein the additive manufacturing technology is a laser metal deposition process.

9. The method according to any one of claims 1 to 3, wherein the step of removing the at least one first portion of the edge (29) is performed by an electrical discharge machining (EDM) process.

10. The method according to any one of claims 1 to 3, wherein the step of removing the at least one first portion of the top wall (32) including the at least one first casting opening (42) and the at least one first portion of the outer wall (23) including the at least one first maintenance opening (44) is performed by electrical discharge machining (EDM).

11. The method according to any one of claims 1 to 3, wherein the height (Ha, Hb) of the removed at least one first portion of the outer wall (23) is greater than or equal to the distance (Da, Db) between the outer surface (33) of the top wall (32) and the wall (52) of the maintenance opening (44) closer to the base (21) of the blade (15).

12. The method according to claim 11, wherein, The height (Ha, Hb) of the removed first portion of the outer wall (23) is less than the distance (Di, Dii) between the outer surface (33) of the top wall (32) and the inner wall (54) of the corresponding cooling conduit (36).

13. The method according to any one of claims 1 to 3, wherein the removed at least one first portion of the top wall (32) and the removed at least one first portion of the outer wall (23) have at least one wedge-shaped profile.

14. The method according to any one of claims 1 to 3, wherein the top wall (32) is provided with at least one second casting opening (42) and the outer wall (23) is provided with at least one second maintenance opening (44), the second maintenance opening (44) being arranged adjacent to the corresponding second casting opening (42); the second casting opening (42) and the second maintenance opening (44) are closed by a second closing element (43); The first casting opening (42) and the first maintenance opening (44) are arranged at the leading edge (27); the second casting opening (42) and the second maintenance opening (44) are arranged at an intermediate position between the leading edge (27) and the trailing edge (28); the method includes: - Remove at least one second portion of the edge (29) near the second casting opening (42) and the second maintenance opening (44); - Remove at least one second portion of the top wall (32) including the at least one second casting opening (42) and at least one second portion of the outer wall (23) including the at least one second maintenance opening (44); - Reconstruct the at least one second portion of the outer wall (23) that was removed and does not have the at least one second maintenance opening (44); - Reconstruct the at least one second portion of the top wall (32) that has been removed and does not have the at least one second casting opening (42); - Reconstruct the removed at least one second portion of the edge (29).

15. The method according to any one of claims 1 to 3, comprising completely removing the edge (29) before removing at least a portion of the top wall (32).

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