The present invention relates to gas turbine engines and, more particularly, to connection structures for accommodating thermal expansion between adjacent sections of a gas turbine engine.
A gas turbine engine generally includes a compressor section, a combustor section, a turbine section and an exhaust section. In operation, the compressor section may induct ambient air and compress it. The compressed air from the compressor section enters one or more combustors in the combustor section. The compressed air is mixed with the fuel in the combustors, and the air-fuel mixture can be burned in the combustors to form a hot working gas. The hot working gas is routed to the turbine section where it is expanded through alternating rows of stationary airfoils and rotating airfoils and used to generate power that can drive a rotor. The expanded gas exiting the turbine section may then be exhausted from the engine via the exhaust section.
The exhaust section of a turbine engine typically includes an exhaust cylinder and an exhaust manifold. During engine operation, hot exhaust gases exiting the turbine section pass through the exhaust cylinder and the exhaust manifold, causing these components to thermally expand in the radial direction. However, the exhaust cylinder and the exhaust manifold may expand at different rates. In some engines, the interface between the exhaust cylinder and the exhaust manifold is rigid at least in the radial direction, thereby inhibiting relative radial movement of these components. Consequently, stresses are placed on the interface, making it susceptible to low cycle fatigue (LCF), which can manifest as cracks, fractures or failures.
In accordance with an aspect of the invention, a flange connection may be provided in a gas turbine engine for joining a turbine exhaust cylinder and a turbine exhaust manifold, the exhaust cylinder including a cylinder flange having an axial face extending radially and facing axially toward the exhaust manifold. The flange connection comprises a stub flange attached to the exhaust manifold and configured to extend in a radial direction outwardly from a centerline of the exhaust cylinder, and the stub flange has a first axial face for engagement with the axial face of the cylinder flange. A plate structure is configured to provide axial retention of the stub flange to the axial face of the cylinder flange, and the plate structure includes a beam portion extending radially inwardly and engaging a second axial face of the stub flange. An engagement of the axial face of the cylinder flange and the beam portion of the plate structure with the stub flange forms an interference fit to provide two degrees of freedom of the stub flange relative to the exhaust cylinder.
In accordance with additional aspects of the invention, one of the degrees of freedom provided by the engagement of the stub flange between the plate structure and the cylinder flange may comprise a rolling movement of the stub flange relative to the exhaust cylinder, and the rolling movement of the stub flange may be provided by the first axial face of the stub flange being defined as a curved surface having a radius about an axis orthogonal to the radial direction. Further, the second axial face of the stub flange may be defined as a curved surface having a radius about an axis orthogonal to the radial direction and the curvature of the first and second axial faces of the stub flange may extend axially outwardly in opposite directions. The plate structure may include an attachment portion located radially outwardly from the beam portion and having fastener openings for receiving fasteners to rigidly affix the plate structure relative to the exhaust cylinder. The stub flange may be movable with one or more degrees of freedom in a plane parallel to the axial face of the exhaust cylinder, including movement in the radial direction relative to the central axis of the exhaust cylinder, and the stub flange may be movable in a rolling movement of the stub flange about an axis orthogonal to the radial direction.
In accordance with further aspects of the invention, the stub flange may comprise a substantially continuous annular member extending around a periphery of the exhaust manifold. The substantially continuous annular member may include an outer peripheral surface and tab structures may extend radially outwardly from the outer peripheral surface. The flange connection may further include spacer segments extending between the axial face of the exhaust cylinder and the plate structure and configured for engagement with the tabs, and an engagement of each tab with one or more respective spacer segments may effect a centering of the stub flange relative to the centerline of the exhaust cylinder. At least two of the tabs may comprise vertical tabs located at upper center and lower center locations, and at least two of the tabs may comprise horizontal tabs located at opposing lateral locations vertically midway between the upper and lower locations on the stub flange.
In accordance with yet a further aspect of the invention, a flange connection may be provided in a gas turbine engine for joining first and second components, the first and second components formed by cylindrical structures defining a hot gas path through the gas turbine engine and the first component including a first flange having an axial face extending radially and facing axially toward the second component. The flange connection comprises a second flange attached to the second component and configured to extend in a radial direction outwardly from a centerline of the first component and having a first axial face for engagement with the axial face of the first flange. A plate structure is configured to provide axial retention of the second flange to the axial face of the first flange, the plate structure including a beam portion extending radially inwardly and engaging a second axial face of the second flange. The second flange is configured to engage between the beam portion and the axial face of the first flange for effecting a rolling movement of the second flange relative to the axial face of the first flange.
In accordance with additional aspects of the invention, the first axial face of the second flange may be defined as a curved surface having a radius about an axis of curvature orthogonal to the radial direction for effecting the rolling movement about an axis parallel to the axis of curvature, and the second axial face of the second flange may be defined as a curved surface having a radius about an axis orthogonal to the radial direction, and the curvature of the first and second surfaces of the second flange may extend axially outwardly in opposite directions. The second flange may comprise a substantially continuous annular member extending around a periphery of the second component and including an outer peripheral surface, and the plate structure may be rigidly affixed to the first component flange with the beam portion of the plate structure located in axially spaced relation to the axial face of the first flange at an attachment location radially outwardly from the outer peripheral surface of the second flange. The second flange may be held in position in an interference fit between the beam portion of the plate structure and the axial face of the first flange. The second flange may comprise a radial portion of a stub flange structure, and the radial portion may be formed continuously with an axial portion, the radial portion defining the first and second axial faces of the second flange and the axial portion forming an axial extension affixed to a periphery of the second component.
While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein:
In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, a specific preferred embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention.
Referring to
Referring further to
Referring to
The plates 42 may be formed as relatively thin members, i.e., relative to the thickness TM of the stub flange 32, and are preferably formed of a high temperature spring material, such as an InconelĀ® alloy spring material. The plurality of plate springs 46a enable the beam portion 46 to apply a substantially uniform predetermined resilient or spring force against the stub flange 32 around the circumference of the stub flange 32 at a plurality of discrete locations, as defined by each of the plate springs 46a. In particular, each plate spring 46a may resiliently flex and apply a force against the stub flange 32 independently of the other plate springs 46a to bias the stub flange 32 in sealing engagement against the cylinder flange 18 to permit movement of the stub flange 32 relative to the cylinder flange 18, as will be described further below.
Referring to
In addition, a retainer 66 may be positioned in engagement with a downstream face 68 of each plate 42, extending radially inwardly such that a radial inner edge 69 of the retainer 66 is generally adjacent to an outer end of a respective gap 48 (
As seen in
It should be understood that the spacing between the plate springs 46a and/or between the plates 42 may be varied from that shown to obtain a desired overall pressure applied against the stub flange 32. For example, a spacing between the plate springs 46a and/or the plates 42 may be greater than that shown herein while still providing sufficient pressure to seal the stub flange 32 against the cylinder flange 18.
Referring to
The first radius of curvature R1 is preferably selected with reference to a predetermined contact pressure between the first axial face 78 of the stub flange 32 and the axial face 56 of the cylinder flange 18, and with reference to the amount of wear that may occur at the contact between the stub flange 32 and the cylinder flange 18. In particular, a lower first radius of curvature R1, i.e., providing a narrower band of contact between the stub flange 32 and the cylinder flange 18, can provide a higher contact pressure to increase the pressure applied for sealing between the stub flange 32 and the cylinder flange 18. On the other hand, an increased pressure and reduced area of contact between the stub flange 32 and the cylinder flange 18 may increase the wear at the contact between these components. Hence, the first radius of curvature R1 is preferably selected to provide a balance between the desired sealing contact pressure and the acceptable wear that may occur at the contact between the stub flange 32 and the cylinder flange 18.
The second radius of curvature R2 is preferably selected to ensure that a substantially uniform biasing force is applied by the beam portion 46 during rolling movement of the stub flange 32. The second radius of curvature R2 may be the same as the first radius of curvature R1, or the first and second radii of curvature R1, R2 may be different from each other.
The contact of the curved axial surfaces 78, 80 with the cylinder flange 18 and the beam portion 46 provides an additional degree of freedom for the stub flange 32, i.e., a degree of freedom in addition to the degree(s) of freedom permitting movement of the stub flange 32 in the plane parallel to the axial face 56 of the cylinder flange 18. The additional degree of freedom of the stub flange 32 is in the form of rolling movement of the stub flange 32 relative to the cylinder flange 18 and the beam portion 46. During operation of the engine, axial movement of the stub support structure 22, such as may be produced by axial forces applied to the axial portion 26 from the exhaust manifold 14, may cause the stub flange 32 to pivot or roll relative to the cylinder flange. The rolling movement of the stub flange 32 may reduce or minimize a prying load applied to the stub flange 32 and increase the low cycle life (LCF) of the stub flange 32. The rolling movement of the stub flange 32 may also reduce or minimize stresses at other locations of the stub flange structure 22, such as at the joint 31 between the stub flange structure 22 and the cone 16 of the exhaust manifold 14. Further, the engagement of the curved first axial surface 78 with the cylinder flange 18 provides a continuous engagement at a predetermined pressure of the stub flange 32 with the cylinder flange 18, and ensures that a consistent contact and substantially uniform pressure are applied between the stub flange 32 and the cylinder flange 18, thereby eliminating the need for a separate seal element between these two structures.
Referring to
As seen in
With regard to the vertical and horizontal tabs 82, 84 illustrated in
The engagement of the vertical tabs 82 with respective adjacent spacer/stabilizer segments 58 and engagement of the horizontal tabs 84 with the respective spacer/stabilizer segments 58H operate to prevent tangential movement of the stub flange 32, as determined with reference to the cylindrical coordinate system, relative to the centerline 20. Further, in the event of a failure of a support, such as a support strap (not shown), for vertically supporting the exhaust manifold 14, the horizontal spacer/stabilizer segments 58H may operate to support the stub flange structure 22 at the horizontal tabs 84 to thereby maintain the exhaust manifold 14 vertically aligned with the exhaust cylinder 12.
The above-described flange connection provides a cantilevered stub flange 32 that permits the stub flange 32 to accommodate differential deflection relative to the cylinder flange 18 during thermal transients to minimize or reduce stresses that may otherwise occur, such as may otherwise occur with rigidly affixed flange structures. The flange connection maintains the stub flange 32 in a predetermined centered position relative to the cylinder flange 18 while permitting expansion radially and in a lateral or circumferential direction of the stub flange 32, as well as permitting rolling movement to avoid a prying load, i.e., beam flexure of the stub flange 32, while maintaining the sealed condition of the stub flange 32 to the cylinder flange 18.
It should be understood that although the aspects of the structure described herein are described with reference to an exhaust cylinder and exhaust manifold, the present invention may be applicable to other cylindrical engine structures that may be joined together and that have different thermal expansion characteristics.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
This application claims the benefit of U.S. Provisional Application No. 61/369,895, filed Aug. 2, 2010, which is incorporated herein by reference.
Number | Date | Country | |
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61369895 | Aug 2010 | US |