Patent Application
20080273964
Not Applicable.
Not Applicable.
The present invention relates generally to gas turbine engines and more specifically to a vane configuration having reduced wear along mating surfaces.
A gas turbine engine typically comprises a multi-stage compressor that compresses air, which has been drawn into the engine, to a higher pressure and temperature. A majority of this air passes to the combustion system, which mixes the compressed and heated air with fuel and contains the resulting reaction that generates the hot combustion gases. These gases then pass through a multi-stage turbine, which, in turn drives the compressor, and possibly a shaft of an electrical generator. Exhaust from the turbine can also be channeled to provide thrust for propulsion of a vehicle.
Typical compressors and turbines comprise a plurality of alternating rows of rotating and stationary airfoils. An example of a vane segment, or stator section, comprising a plurality of airfoils positioned between an inner platform and outer platform is shown in
The stationary airfoils, or vanes, direct the flow of air in a compressor or hot combustion gases in a turbine onto a subsequent row of rotating airfoils, or blades, at the proper orientation in order to maximize the output of the compressor or turbine. To minimize manufacturing costs as well as to improve response to thermal gradients and thermal deflections, more recent engine designs utilize a plurality of vane assemblies in the compressor or turbine. These vane assemblies include at least one airfoil bounded on either end by a section of an outer platform and an inner platform, with the inner platform located closer to the engine centerline. Each of the vane assemblies typically span a few degrees and have a shorter arc length than the prior art half-ring segments. Depending on how the vane assemblies are mounted in the engine, significant movement can occur between adjacent vane assemblies causing undesirable contact and wear. When vane assemblies are mounted at or near their outer platform, thereby causing them to essentially hang free at the inner platform, relatively large movement can occur at the inner platform due to the distance of the inner platform from the mounting location, vibrations, and differences in thermal gradients between the adjacent vane assemblies. When such motion occurs between adjacent vane assemblies, significant wear can occur along the mating surfaces due to the mating surfaces essentially damping the vibrations. Significant wear is also found at the hooks that hold the vane assemblies in place due to the amount of movement at the inner platform and the surface-to-surface contact at the mounting location. This excessive wear can lead to premature repair or require replacement of the vane assemblies.
What is needed is a vane assembly configuration that reduces the amount of wear that occurs along mating faces of adjacent vane assemblies and at the mounting location so as to increase the life of the vane assemblies.
The present invention is defined by the claims below. Embodiments of the present invention solve at least the above problems by providing a system and method for, among other things, reducing vibration and wear along adjacent platform surfaces and mounting locations of a plurality of vane assemblies in a gas turbine engine.
The present invention seeks to improve the interaction between mating faces of adjacent gas turbine vanes by increasing the surface area where contact between the adjacent vanes occurs. In a first embodiment of the present invention, a gas turbine engine having a plurality of vane assemblies extending about an engine centerline having inner and outer arc-shaped platforms with at least one airfoil extending therebetween are disclosed. First and second extension plates extend radially inward from the inner platform and have a plurality of first openings, and are fixed to first and second side faces of the inner arc-shaped platform. Positioned between the extension plates, and having a plurality of second openings, is at least one shim plate. At least one fastener is positioned so as to secure the extension plates and shim plate together in a removable manner, thereby increasing the surface area along which adjacent vane assemblies interact.
In an alternate embodiment of the invention, a shim plate assembly for use in a gas turbine engine is disclosed. The shim plate assembly comprises first and second extension plates having a first plurality of openings and at least one shim plate positioned therebetween, with the shim plate having a second plurality of openings. The axial length of the shim plate is greater than the length of the extension plates. A locating pin is positioned proximate the mid-span of the shim plate and extension plates so as to properly position the plates relative to one another while at least one fastener is positioned through the first and second plurality of openings in the plates so as to fix the extension plates and at least one shim plate together.
In yet another alternate embodiment, a method of reducing wear along mating surfaces of a vane segment is disclosed. A slot is cut through a vane segment inner arc-shaped platform from the surface opposite of the airfoils and circumferentially between adjacent airfoils. A block, pre-machined to include a first plurality of openings, is fixed in the slot. The vane segment is then cut, between adjacent airfoils, through the inner and outer arc-shaped platforms, including the machined block. As a result, a plurality of vane assemblies are formed, with each vane assembly having an extension plate fixed to each side face of the vane assembly inner platform. A locating pin is then placed in one of the first plurality of openings and at least one shim plate is inserted between the extension plates. The extension plates are then fixed to the at least one shim plate by passing at least one fastener through the remaining openings in the extension plates and corresponding openings in the shim plate.
In accordance with these and other objects, which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings. Additional advantages and features of the present invention will be set forth in part in a description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned from practice of the invention.
The present invention is described in detail below with reference to the attached drawing figures, wherein:
The subject matter of the present invention is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different steps or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the terms “step” and/or “block” may be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly described.
The present invention is shown in detail in
Referring initially to
As previously discussed, the present invention reduces wear on the mating platform surfaces by increasing the surface area at which contact occurs, so as to provide more damping. This is accomplished for a plurality of vane assemblies through a sim plate assembly 45. A first extension plate 46 is fixed to the first side face 42, while a second extension plate 48 is fixed to the second side face 44. The extension plates 46 and 48 have a first axial length and are preferably fixed to the inner arc-shaped platform 28 by electron beam (EB) welding. Such a process ensures a clean and complete weld through the thickness of the platform and the extension plate. In order to have the best weld properties, it is preferred that the extension plate is fabricated from a material having similar properties as the vane assemblies. The extension plates 46 and 48 extend radially inward from the inner arc-shaped platform 28 and have a first plurality of openings 50 comprising at least two openings. The present invention also comprises at least one shim plate 52 that has a second axial length and second plurality of opening 54 with a plate thickness 56 and at least one fastener 58. As it can be seen from
The at least one shim plate 52, which is also fabricated from a material similar to the extension plates and the vane assembly, is positioned between the first and second extension plates, 46 and 48, of adjacent vane assemblies. That is, with each vane assembly having a first side face 42 and a second side face 44, the first and second side faces would normally contact one another, and therefore, the first and second extension plates, 46 and 48, of adjacent vane assemblies provide increased areas for contact. The shim plate 52 is positioned such that the second plurality of openings 54, which also comprises at least two openings, correspond to the first plurality of openings 50 and the at least one fastener 58 is positioned at least partially through the first and second openings, 50 and 54, so as to fix the adjacent vane assemblies together. The shim plate 52, as it can be seen from
Located through one of the at least two openings in extension plates 46 and 48 and through the shim plate 52 is a locating pin 60. The locating pin 60 helps to position adjacent vane assemblies in the proper orientation while fasteners 58 are installed through the first and second plurality of openings 50 and 54 in the extension plates and the shim plate. The locating pin 60 is intended to be contained within the shim plate assembly 45 and not to become dislodged during engine operation. This can be accomplished by tack welding the locating pin 60 to one of the extension plates 46 or 48. Alternatively, the locating pin 60 can be contained by a retaining plate 62, through which at least one fastener 58 passes.
In one embodiment of the present invention, an apparatus is disclosed for reducing wear caused by vibration along mating surfaces of adjacent turbine vane assemblies 22. In another embodiment, a method of reducing wear along mating surfaces of a vane segment is provided. In this method, an existing vane segment 10, similar to a half-ring segment of the prior art, is modified to incorporate one or more shim plate assemblies 45 to reduce wear on the inner platforms and along the mounting locations at the outer platform. The method comprises providing a vane segment 10 having an outer arc-shaped platform 14, a plurality of airfoils 16 extending radially inward from the outer arc-shaped platform 14, and an inner arc-shaped platform 12 fixed to the plurality of airfoils 16 opposite the outer arc-shaped platform 14.
Referring to
Once the block is fixed in the slot 29, the vane segment is cut between the adjacent airfoils, through both the inner and outer arc-shaped platforms and the machined block. The cutting of the vane segment 10 forms a plurality of vane assemblies 22 with the machined block split into two parts, thereby forming two extension plates 46 and 48, with each extension plate remaining fixed to the inner arc-shaped platform 28.
As a result of cutting the vane segment into individual assemblies 22, the natural tendency of an assembly 22 is to spring back to a more relaxed position and not maintain as much of the arc shape in the platforms. In order to help the vane assemblies 22 maintain their shape and to assist in properly re-aligning the vane assemblies 22 into a segment 20, a locating pin 60 is placed in one of the first plurality of openings 50. The locating pin 60 can be placed in any of the first openings 50. However, if the first plurality of openings 50 comprises three openings, then it is preferred that the locating pin 60 be placed in the opening closest to the center of the extension plates 46 and 48. Next, at least one shim plate 52 having a second plurality of openings 54 is inserted between the extension plates 46 and 48. Depending on the vane assembly configuration and expected wear, the at least one shim plate 52 may also include a wear reduction coating, such as an Aluminum Bronze coating, applied to surfaces of the shim plate 52 that mate with the extension plates. The shim plate(s) 52 has a thickness that corresponds to the thickness of material lost when the vane segment was cut into individual assemblies 22. Depending on the amount of material lost during the cutting process, more than one shim plate 52 may be required. The extension plates 46 and 48 and at least one shim plate 52 are fixed together by passing at least one fastener 58 through the remaining plurality of first and second openings 50 and 54.
From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects set forth above, together with other advantages which are obvious and inherent to the system and method. While the invention has been described in what is known as presently the preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment but, on the contrary, is intended to cover various modifications and equivalent arrangements within the scope of the following claims.
