The subject matter disclosed herein relates to turbine engines. More particularly, the subject matter relates to modifying of turbine engine parts.
In a gas turbine engine, a compressor provides pressurized air to one or more combustors wherein the air is mixed with fuel and burned to generate hot combustion gas. These gases flow downstream to one or more turbines that extract energy therefrom to produce a mechanical energy output as well as power to drive the compressor. Over time, turbine parts, such as parts of the turbine, may experience fatigue, due to extreme conditions within the turbine, including high temperatures and pressures caused by flow of hot gas. In particular, certain turbine parts, such as buckets located on a turbine rotor, may experience fatigue that requires servicing or replacement.
In cases where reference locations in fatigued areas utilize welding or other heat-based operation, the repair process may further fatigue the local area. Thus, repair of some reference locations occurring due to wear and tear is not feasible. Replacement of these parts can be a costly, especially if fatigue in selected areas occurs in several parts, such as buckets on a rotor wheel.
According to one aspect of the invention, a method is provided for modifying an airfoil shroud located at a tip of a blade of an airfoil, the airfoil shroud having a first end edge, a second end edge, a leading edge and a trailing edge, the method including: locating a reference location in the second end edge of the airfoil shroud, the reference location being proximate a seal rail extending circumferentially from a radially outer surface of the airfoil shroud; and forming a relief cut in the airfoil shroud to remove the reference location to thereby modify the airfoil shroud.
According to another aspect of the invention, a bucket is provided including: an airfoil having an airfoil axis; a shroud disposed at a tip of the airfoil, the shroud having a first end edge, a second end edge, a leading edge and a trailing edge; a seal rail extending circumferentially from a radially outer surface of the shroud; and a recess formed in the second end edge proximate the seal rail and on the leading edge of the airfoil.
According to another aspect of the invention, a turbine engine is provided including: a rotor; a bucket to be placed on the rotor, the bucket including: an airfoil having an airfoil axis; a shroud disposed at a tip of the airfoil, the shroud having a first end edge, a second end edge, a leading edge and a trailing edge; a seal rail extending circumferentially from a radially outer surface of the shroud; and a recess formed in the second end edge proximate the seal rail and the leading edge of the airfoil.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
In an aspect, the combustor 104 uses liquid and/or gas fuel, such as natural gas or a hydrogen rich synthetic gas, to run the turbine engine. For example, fuel nozzles 110 are in fluid communication with a fuel supply 112 and pressurized air from the compressor 102. The fuel nozzles 110 create an air-fuel mix, and discharge the air-fuel mix into the combustor 104, thereby causing a combustion that creates a hot pressurized exhaust gas. The combustor 104 directs the hot pressurized exhaust gas through a transition piece into a rotor and stator assembly, causing turbine 106 to rotate as the gas exits nozzles and is directed onto the turbine buckets or blades. The rotation of the buckets coupled to the rotor in turbine 106 causes the shaft 108 to rotate, thereby compressing the air as it flows into the compressor 102.
In embodiments, one or more relief cuts may be formed in a shroud of an airfoil in the turbine engine. In an embodiment, the shroud is positioned on an airfoil such as a turbine bucket or a nozzle. The one or more relief cuts may be formed to modify the shroud and remove at least one of two reference locations in the airfoil shroud. In an embodiment, the at least one reference location is a flaw, such as a crack or missing material, that has been identified on the shroud. The at least one reference location may be caused by fatigue from exposure to extreme heat and pressure during turbine engine operation. In an embodiment, the relief cuts are formed without welding the shroud, thus reducing incidence of additional fatigue that may be introduced to the shroud by a welding process. In one embodiment, the relief cuts provide a structurally sound repair to the airfoil shroud to enable reuse and reinstallation of the airfoil following forming of the relief cuts. Accordingly, the repair process provides savings in time and costs when servicing the airfoil.
As used herein, “downstream” and “upstream” are terms that indicate a direction relative to the flow of working fluid through the turbine. As such, the term “downstream” refers to a direction that generally corresponds to the direction of the flow of working fluid, and the term “upstream” generally refers to the direction that is opposite of the direction of flow of working fluid. In addition, the terms “leading edge” and “trailing edge” indicate a position of a part relative to the flow of working fluid. Specifically, a leading edge of an airfoil encounters hot gas flow before a trailing edge of the airfoil. The term “radial” refers to movement or position perpendicular to an axis or center line of a reference part or assembly. It may be useful to describe parts that are at differing radial positions with regard to an axis. In this case, if a first component resides closer to the axis than a second component, it may be stated herein that the first component is “radially inward” of the second component. If, on the other hand, the first component resides further from the axis than the second component, it can be stated herein that the first component is “radially outward” or “outboard” of the second component. The term “axial” refers to movement or position parallel to an axis. Finally, the term “circumferential” refers to movement or position around an axis. Although the following discussion primarily focuses on gas turbines, the concepts discussed are not limited to gas turbines and may apply to any suitable rotating machinery, including steam turbines. Accordingly, the discussion herein is directed to gas turbine embodiments, but may apply to steam turbines and other turbomachinery.
In embodiments, the shroud 208 is a flat plate supported towards its center by the blade 202, where the shroud 208 is subject to high temperatures and centrifugal loads during turbine operation. As a result, portions of the shroud 208 may experience fatigue over time, where embodiments of the modifying process described herein repair fatigue, such as reference locations in the airfoil shroud.
The seal rail 412 has fillets 414 on each side extending from the radially outer surface 416 to provide support for the seal rail 412. During operation of the turbine engine, fatigue caused by high pressures and temperatures can cause formation of a reference location B (410) that includes a deformation such as a crack and a reference location A (420) in the airfoil shroud 400 that includes a deformation such as a crack. In an embodiment, reference location B (410) is located on the trailing edge proximate the fillet 414 of seal rail 412 near the first end edge 406. Reference location A (420) is located on the leading edge near the fillet 414 of seal rail 412 near the second end edge 408. In general, the deformation at reference location A (420) may appear in the shroud after the deformation appears at reference location B (410) according to the normal use of the shroud 400. In cases where reference location A (420) is proximate structural regions, such as fillets 414, a relief cut (502,
Accordingly,
In embodiments, the modifying process services or repairs the airfoil shroud 400 without a welding process, thus ensuring structural integrity is maintained in the region repaired. The structural integrity provided by the relief cuts 500 and 502 enables the airfoil shroud 400 to be reinstalled in the bucket row of the rotor and to withstand loads and stress caused by extreme temperatures and pressures. By forming the one or more relief cuts 500 and 502 as arc-shaped relief cuts, the resulting geometry, including the fillet 414, the first end edge 406 and the second end edge 408, maintains structural integrity to improve part life for the shroud, thus reducing operating costs for the turbine engine. In contrast, repair techniques that use a welding process may further fatigue the region being repaired. In some cases where welding is used for repair, welding may actually degrade the structural integrity of affected regions, thus leading to replacement of the entire airfoil and leading to increased operational costs. The service process utilizing relief cut 500 and relief cut 502 may be used to repair a reference location located in any suitable location, such as first end edge 406, second end edge 408, leading edge 402 and trailing edge 404. In various embodiments, the relief cuts 500 and 502 may remove a portion of the fillet 414 without resulting in significant structural losses. In other embodiments, at least one of the relief cuts 500 and 502 may be formed along a shroud edge and outside of the fillet 414. In cases where at least one of the relief cuts 500 and 502 forms an arc-shaped recess, a radius of the arc may vary depending on application needs.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
The present application is a continuation-in-part of U.S. patent application Ser. No. 13/685,950, titled “METHOD FOR MODIFYING A AIRFOIL SHROUD AND AIRFOIL” filed on Nov. 27, 2012, the disclosure of which is incorporated by reference herein in its entirety.
Number | Date | Country | |
---|---|---|---|
Parent | 13685950 | Nov 2012 | US |
Child | 14046417 | US |