Not applicable.
Not applicable.
This invention relates to a transition duct for a gas turbine engine, specifically to a novel and improved profile for a transition duct that results in lower operating stresses and extended component life.
In a typical can annular gas turbine engine, a plurality of combustors are arranged in a generally annular array about the engine. The combustors receive pressurized air from the engine's compressor, adds fuel to create a fuel/air mixture, and combusts that mixture to produce hot gases. The hot gases exiting the combustors are utilized to turn a turbine, which is coupled to a shaft that drives a generator for generating electricity.
The hot gases are transferred from the combustor to the turbine by a transition duct. Due to the position of the combustors relative to the turbine inlet, the transition duct must change cross-sectional shape from a generally cylindrical shape at the combustor exit to a generally rectangular arc-like shape at the turbine inlet. In addition, the transition duct undergoes a change in radial position, since the combustors are typically mounted outboard of the turbine. Extreme care must be taken with respect to the design of these ducts in order to avoid sharp geometric changes, otherwise regions of high stress and stress concentrations can occur. The combination of complex geometry changes as well as extreme mechanical and thermal loading seen by the transition duct can create a harsh operating environment that can lead to premature deterioration, requiring repair and replacement of the transition ducts. To withstand the hot temperatures from the combustor gases, transition ducts are typically air-cooled. A variety of methods are available to provide cooling such as through internal channels, impingement cooling, or effusion cooling.
Severe cracking, resulting in component failure and forcing engine shutdown, has been known to occur in transition ducts having extremely sharp geometry changes and internal air-cooled channels. In such an incident, the engine requires transition ducts replacement or repair prior to returning to operational status. The present invention seeks to overcome the shortfalls of these prior art designs.
The present invention is defined by the claims below. Embodiments of the present invention solve at least the above problems by providing an apparatus for a transition duct having a geometric profile that results in lower operating stresses and improved component life.
In an aspect of the present invention, a transition duct is provided having an inlet ring, an aft frame, and a panel assembly having an internal profile defined by a series of X, Y, and Z Cartesian coordinates taken along a sweep angle θ.
A novel and improved transition duct having an enhanced profile for improved performance and durability is provided. The internal flowpath geometry of the transition duct has been configured to remove areas of sharp geometric change. The sharp geometric changes, in combination with high thermal and mechanical loading, caused regions of high steady and vibratory stresses and local stress concentrations in prior art ducts that often lead to cracking and premature failure. Furthermore, due to a rounder profile, certain natural frequencies of the transition duct are raised to avoid potential vibratory issues.
A variety of cooling methods can be used in combination with the enhanced profile of the present invention transition duct. In an embodiment, the cooling system continues to use air, but the air is directed through a plurality of effusion holes in the panel assembly of the transition duct. Effusion cooling provides more uniform cooling of the transition duct than the plurality of internal cooling channels used in the prior art, which were also a source of stress concentrations.
In an embodiment of the present invention, there is provided a transition duct with a panel assembly having an inlet end of generally circular cross section and an outlet end having a generally rectangular arc-like cross section with an uncoated internal profile substantially in accordance with the coordinate values θ, X, Y, and Z as set forth in Table 1. The origin of the coordinate system is positioned at the center of the panel assembly inlet end along a centerline axis. It will be appreciated that the coordinate values given are for manufacturing purposes, in a room temperature condition. The coordinate values X, Y, and Z in Table 1 are standard Cartesian coordinates, and correspond to a specific sweep angle θ, which together, define a cross section of the panel assembly. Each cross section is joined smoothly with adjacent cross sections to define a panel assembly for the transition duct. It will also be appreciated that as the transition duct transfers hot combustion gases from a combustor to the turbine inlet, the transition duct absorbs heat, and therefore the coordinates provided in Table 1 do not necessarily correspond to the panel assembly position when in operation at an elevated temperature.
In an alternate embodiment, there is provided a transition duct with a panel assembly having an inlet end of generally circular cross section and outlet end having a generally rectangular arc-like cross section with an uncoated internal profile within an envelope of +/−0.250 inches in a direction normal to any surface of the panel assembly substantially in accordance with the coordinate values θ, X, Y, and Z as set forth in Table 1. The origin of the Cartesian coordinate system is positioned at the center of the panel assembly inlet end along a centerline axis. A distance of +/−0.250 inches in a direction normal to any surface location along the panel assembly defines an envelope for this particular panel assembly and ensures that manufacturing tolerances are accommodated within the envelope of the panel assembly. As with the embodiment previously disclosed, it will be appreciated that the coordinate values given are for manufacturing purposes, in a room temperature condition. Each set of coordinate values X, Y, and Z in Table 1 is in standard Cartesian coordinates and corresponds to a specific sweep angle θ, which, when taken together defines a cross section of the panel assembly. Each cross section is joined smoothly with adjacent cross sections to define a panel assembly for the transition duct. It will also be appreciated that as the transition duct transfers hot combustion gases from a combustor to the turbine inlet, the transition duct heats up and therefore the Cartesian coordinates for a given θ value provided in Table 1 may not necessarily correspond to the panel assembly position when in operation at an elevated temperature.
The instant invention will now be described with particular reference to the accompanying drawings.
Illustrative embodiments of the present invention are described in detail below with reference to the attached drawing figures, which are incorporated by reference herein and wherein:
a, 6b, 6c, and 6d are section views taken through the panel assembly of the present invention at various sweep angles.
Embodiments of the present invention provide apparatus for a gas turbine transition duct that are configured geometrically to have lower operating stresses. Lower stresses, both mechanical and thermal, result in improved component life.
Referring to
The present invention is shown in
The panel assembly 23, formed from the first panel 24 and the second panel 25, has an uncoated internal profile substantially in accordance with coordinate values X, Y, and Z as set forth in Table 1, carried only to three decimal places. Although the preferred unit of measure for the values given in Table 1 is inches, those skilled in the art will appreciate that the values of Table 1 for X, Y, and Z can be scaled up or down depending on the diameter of the particular combustion liner with which the present invention is to be used. This uncoated internal profile provides an optimized transition from a generally circular inlet end to a generally rectangular arc-like outlet end over the allowable axial and radial distance for a gas turbine engine, such that high steady stresses and stress concentrations in the transition duct 20 are minimized. For the purpose of describing the present invention, the coordinate values X, Y, and Z of Table 1 are taken at various sweep angles θ wherein θ is an angle measured from the inlet end 21 and increases to its maximum value at the outlet end 22. Sweep angle θ originates at an intersection line 90 formed from a first plane 100, that is defined by the inlet end 21 of the panel assembly 23, and a second plane 102, that is defined by the outlet end 22 of the panel assembly 23, as shown in
For the data listed in Table 1 a plurality of wireframe sections can be created when applying a best-fit curve to the section data for each sweep angle θ. For example,
An additional feature of the transition duct 20 is a protective two-layer coating applied along the internal profile of the panel assembly 23 to protect the transition duct 20 from deterioration associated with prolonged exposure to elevated temperatures. The two-layer air plasma sprayed coating preferably comprises a MCrAlY bond coating applied directly to the panel assembly 23 and a Yttra Stabilized Zirconia top coating applied over the bond coating, the combined coating having a thickness of at least 0.019 inches. The two-layer coating is preferably applied once the panel assembly 23 has been formed and welded in accordance with the profile as defined in Table 1.
In an alternate embodiment of the present invention there is provided a transition duct similar to that of the preferred embodiment except for the uncoated internal profile of the panel assembly 23 is within an envelope of +/−0.250 inches in a direction normal to any surface of the panel assembly substantially in accordance with the Cartesian coordinate values X, Y, and Z as set forth in Table 1. A distance of +/−0.250 inches in a direction normal to any surface of the panel assembly thereby defines a profile envelope for this specific transition duct panel assembly. This envelope ensures that all reasonable manufacturing tolerances are accommodated within the profile.
The X, Y, Z Cartesian coordinate data and corresponding sweep angles θ are summarized in the following Table 1.
Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of the present invention. Embodiments of the present invention have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from the scope of the present invention.
It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims.
Number | Name | Date | Kind |
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5983641 | Mandai et al. | Nov 1999 | A |
6644032 | Jorgensen et al. | Nov 2003 | B1 |
20060069533 | Florea et al. | Mar 2006 | A1 |
Number | Date | Country | |
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20070240422 A1 | Oct 2007 | US |