Patent Application
20140147285
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, gas turbine engine parts 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 the part is a complex part that was manufactured using close tolerance, the part can have deformations due to wear and tear. The deformed part can be difficult to fixture for servicing due to a variation in dimension caused by deformation.
According to one aspect of the invention, a fixture for an airfoil shroud having a first end edge, a second end edge, a leading edge, a trailing edge, a radially outer side and a radially inner side with respect to a rotor axis of a bucket having the airfoil shroud is provided. In embodiments, the airfoil is a turbine bucket in a rotor section of a turbine engine. The fixture includes a base plate configured to be disposed on one of the radially outer side and radially inner side of the airfoil shroud, a first member extending from the base plate configured to locate and abut the first end edge, wherein the first end edge is proximate a trailing edge of an airfoil of the bucket, a second member extending from the base plate configured to locate and abut a side of a seal rail circumferentially extending from the radially outer side of the airfoil shroud, wherein surfaces of the first end edge and the side of the seal rail are substantially parallel to an axis of the airfoil, a third member extending from the base plate configured to locate and abut the radially outer side of the airfoil shroud and a template recess formed in the base plate proximate the first end edge to define a geometry of a relief cut in the trailing edge of the airfoil shroud.
According to another aspect of the invention, a method for modifying an airfoil shroud of an airfoil having an airfoil axis, the airfoil shroud having a first end edge, a second end edge, a leading edge, a trailing edge, a radially outer side and a radially inner side with respect to a rotor axis of a rotor of the airfoil is provided. The method includes positioning a base plate proximate the airfoil shroud, locating an axial position, with respect to the rotor axis, of the airfoil shroud by abutting a first end edge, wherein the first end edge is proximate a trailing edge of the airfoil shroud, locating a circumferential position, with respect to a circumference of the rotor, of the airfoil shroud by abutting a side of a seal rail circumferentially extending from the radially outer side of the airfoil shroud, wherein surfaces of the first end edge and the side of the seal rail are substantially parallel to the airfoil axis, locating an axial position, with respect to the airfoil axis, by abutting the radially outer side of the airfoil shroud and defining a template for a geometry of a relief cut for the airfoil shroud.
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 rotation as the gas exits nozzles where the gas is then directed to the 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, a relief cut is 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 relief cut is formed to repair the shroud and remove a flaw, such as a crack, that has been identified on the shroud. The flaw may be caused by fatigue from exposure to extreme heat and pressure during turbine engine operation. In an embodiment, the relief cut is 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 cut provides a structurally sound repair to the airfoil shroud to enable reuse and reinstallation of the airfoil following forming of the relief cut. Accordingly, the repair process provides savings in time and costs when modifying the airfoil.
In embodiments, the repair process uses a fixture to properly locate the relief cut on the airfoil shroud. The fixture locates surfaces and portions of the shroud to provide a template for forming the relief cut in the shroud. In an embodiment, the fixture enables repair of the airfoil without referencing locations on the airfoil or base of the bucket, where portions of the airfoil can deform and move relative to the shroud over time. Thus, by fixturing to the shroud directly, a position of the shroud relative to the fixture is provided to enable accurate placement of the template used for forming the relief cut.
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.
As depicted, the shroud 208 has a radially outer side 214 and a radially inner side 216. In addition, an airfoil axis 210 extends longitudinally through the blade 202. 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 modify a reference location, such as to repair flaws 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 flaw 410 in the airfoil shroud 400. In an embodiment, the flaw 410 is a crack proximate the fillet 414 of seal rail 412. In cases where the flaw 410 is proximate structural regions, such as fillets 414, a relief cut may be used to repair and remove the flaw 410, as described below. The relief cut may be formed without performing a weld process on the shroud. In contrast, processes using welding to repair flaws may adversely affect material structural regions of the airfoil shroud 400, such as fillets 414.
Accordingly,
In embodiments, the modifying process 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 cut 500 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 arc-shaped relief cut 500, the resulting geometry, including the fillet 414 and first end edge 406, 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 the relief cut 500 may be used to repair a flaw located in any suitable location, such as second end edge 408, leading edge 402 and trailing edge 404. In embodiments where the relief cut 500 is in the first end edge 406, the relief cut 500 may remove a portion of the fillet 414 without resulting in significant structural losses. In other embodiments, the relief cut 500 is formed along a shroud edge and outside of the fillet 414. In cases where the relief cut 500 forms an arc-shaped recess, a radius of the arc may vary depending on application needs.
In an embodiment, the locating members 604, 606, 608, 610, 612, 614, 616, and 618 position the airfoil shroud 400 to enable a template 628 to define a geometry for the relief cut 500 in the first end edge 406 of the shroud. In an embodiment, the blade 202 (
The flow diagram depicted herein is just one example. There may be many variations to this diagram or the steps (or operations) described therein without departing from the spirit of the embodiment. For instance, the steps may be performed in a differing order or steps may be added, deleted or modified.
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.
