Patent Application
20090053046
The present disclosure relates generally to turbine exhaust systems, and particularly to turbine exhaust diffusers.
Current gas turbine engines utilize an exhaust frame to support an exterior exhaust housing, or stator casing. The exhaust frame and exterior housing are made from structural steel, which is not capable of withstanding a temperature of turbine exhaust gases. Therefore, diffusers made from a material that is capable of withstanding the temperature of exhaust gases are utilized to shield the exhaust frame and exterior housing from exposure to the temperature of exhaust gases. Furthermore, blowers may be used to provide cool air for additional shielding of the exhaust frame from the temperature of exhaust gases. In conjunction with blowers, seals between the diffuser and the exhaust frame can be used to direct the cool air to appropriate locations and to reduce undesired leakage. Attention to control challenges that result from differential thermal expansion of the frame and the diffuser can yield complex and costly design and operational solutions. Accordingly, there is a need in the art for a turbine exhaust arrangement that overcomes these drawbacks.
An embodiment of the invention includes a turbine diffuser. The turbine diffuser includes a diffuser segment having a forward end and an aft end with a flange disposed at the aft end of the diffuser segment. The diffuser segment is joinable to an adjacent diffuser segment via the flange, which includes a seal retainer that is securedly connectable in a radial direction with a seal.
Another embodiment of the invention includes a turbine exhaust system. The turbine exhaust system includes a frame, an outer stator supported by the frame, and a turbine diffuser disposed within the outer stator. The turbine diffuser includes a diffuser segment having a forward end and an aft end and a flange including a seal retainer, the flange disposed at the aft end of the diffuser segment, which is joinable to an adjacent diffuser segment via the flange. The turbine exhaust system further includes a seal having a first end and a second end. The first end of the seal is securedly connected in a radial direction with the seal retainer and the second end of the seal is securedly connected with the frame.
Another embodiment of the invention includes a method of sealing a turbine exhaust system. The method includes securedly connecting in a radial direction a first end of a seal in a seal retainer of a flange disposed at an aft end of a diffuser segment, the diffuser segment being joinable to an adjacent diffuser segment via the flange. The method further includes securedly connecting a second end of the seal to a frame supporting an outer stator of the exhaust system.
These and other advantages and features will be more readily understood from the following detailed description of preferred embodiments of the invention that is provided in connection with the accompanying drawings.
Referring to the exemplary drawings wherein like elements are numbered alike in the accompanying Figures:
An embodiment of the invention provides a turbine diffuser arrangement that includes a connection flange incorporating a seal retainer. A seal disposed between the exhaust frame and the seal retainer directs and reduces undesired loss of cooling air. In an embodiment, thermal expansion of the diffuser relative to the exhaust frame results in a reduced thermal contact area between the seal and the retainer, thereby reducing a transfer of heat therebetween.
As used herein to describe relative position, the term “aft” shall refer to a relative position that is downstream, or located toward an exit end 35 along an axial centerline 40 of the turbine engine 8. As used herein to describe relative position, the term “forward” shall refer to a relative position that is upstream, or located toward an inlet end 45 along the axial centerline 40 of the turbine engine 8.
Referring now to
In one embodiment, the first end 135 of the seal 115 is oriented axially (aligned with an axial direction A) facing toward the aft end 80 of the diffuser segment 70, and the second end 137 of the seal 115 is oriented radially (aligned with the radial direction R) facing outward, toward the frame 65.
The seal retainer 120 includes an opening 130 that faces the forward end 75 of the diffuser segment 70 (also herein referred to as a “forward facing opening”). In one embodiment, the forward facing opening 130 is an axial opening. The first end 135 of the seal 115 is disposed in the forward facing opening 130. In an embodiment, the forward facing opening 130 includes three sides 140, 145, 150, which define for example, the forward facing opening 130 as a forward facing slot 130. The seal retainer 120 is securedly connectable with the seal 115 and secures or constrains displacement of the seal 115 in the radial direction R. The forward facing opening 130 provides a degree of freedom between the seal 115 and the seal retainer 120 in the axial direction A, which is generally aligned with the axial centerline 40 of the turbine engine 8 (best seen with reference to
Referring now to
As described above, it desirable to reduce a flow of heat from the exhaust gases to the exhaust frame 65, as the exhaust frame 65 is made from material that is not well suited to exposure to turbine exhaust gas temperatures. Therefore, particularly during starting of the turbine engine 8, there are differential thermal expansions of the diffuser 55 (exposed to the temperature of turbine exhaust gases) relative to the exhaust frame 65, which is shielded by the diffuser 55 from exposure to the temperature of the turbine exhaust gases. A heat conduction path 155 depicts an example of heat transfer from the diffuser segment 70 through the seal retainer 120 of the flange 85, into the seal 115, and to the frame 65. A length of axial overlap 160 defines an area of contact between the first end 135 of the seal 115 and the seal retainer 120. The area of contact provides a thermal contact area, such that the greater the length of overlap 160, the greater the amount of heat that may be transferred via the heat conduction path 155 from the diffuser segment 70 to the frame 65 at a given temperature of the diffuser segment 70.
As a result of thermal expansion from exposure to the temperature of the turbine exhaust gases, the aft end 80 of the diffuser segment 70 is responsive to an increasing temperature of the diffuser segment 70 to translate in an aft direction 165 relative to the exhaust frame 65. Therefore, because of the axial degree of freedom between the seal 115 and the seal retainer 120, the seal retainer 120 is responsive to the aft translation of the aft end 80 of the diffuser segment 70 to translate aft in an axial direction relative to the seal 115. Aft translation of the seal retainer 120 relative to the seal 115 results in partial disengagement of the first end 135 of the seal 115 within the seal retainer 120 opening 130, thereby reducing the length of overlap 160, and the thermal contact area between the first end 135 of the seal 115 and the seal retainer 120. Accordingly, reducing the thermal contact area in response to the increasing temperature of the diffuser segment 70 reduces the amount of heat transferred by the heat conduction path 155 at a given temperature. For example, as the temperature of the diffuser segment 70 increases and the seal retainer 120 partially disengages from the first end 135 of the seal 115, the amount of heat transferred from the diffuser segment 70 to the exhaust frame 65 via the seal 115 is less than that in the absence of the response of the diffuser segment 70 and seal retainer 120 to the increasing temperature of the diffuser segment 70.
With reference to
In view of the foregoing, the turbine exhaust system 50 facilitates a method of sealing the diffuser segment 70 to the exhaust frame 65. Referring now to
In an embodiment, the method begins at Step 210 by securedly connecting the first end 135 of the seal 115 in the seal retainer 120 of the flange 85 of the diffuser segment, 70 which is disposed at the aft end 80 of the diffuser segment 70. The diffuser segment 70 is connectable to the adjacent diffuser segment 90 via the flange 85. An embodiment of the method concludes at Step 220 with securedly connecting the second end 137 of the seal 115 to the frame 65, which supports the stator casing 60 (best seen with reference to
In an embodiment of the method, the securedly connecting the first end 135 of the seal 115, at Step 210, includes disposing the first end 135 of the seal 115 in the forward facing slot 130 of the seal retainer 120. An embodiment of the method further includes translating the aft end 80 of the diffuser segment 70 in an aft direction relative to the frame 65 in response to increasing temperature of the diffuser segment 70. Further, in response to the aft translation of the aft end 80 of the diffuser segment 70, the method includes reducing the length of overlap 160 that defines the thermal contact area between the first end 135 of the seal 115 and the seal retainer 120, thereby reducing an amount of heat transferred from the diffuser segment 70 to the exhaust frame 65 via the heat conduction path 155 of the seal 115.
An embodiment of the method provides securedly connecting, at Step 210, the first end 135 of the seal 115 oriented axially toward the aft end 80 of the diffuser segment 70 with the seal retainer 120 and securedly connecting, at Step 220, the second end 137 of the seal 115 oriented radially outward, toward the frame 65 with the frame 65.
As disclosed, some embodiments of the invention may include some of the following advantages: reducing cooling blower capacity requirements by reducing unintended cooling air leakage; reducing a thermal contact area of a seal in response to increasing diffuser temperature via a responsive sealing arrangement; and reducing transient thermal stresses and displacements associated with a seal retainer disposed proximate a bolted vertical flange by incorporating the seal retainer into the flange.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best or only mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
