The present invention relates to gas turbine engines. More particularly, embodiments of the present invention relate to an apparatus and method for lowering thermal and mechanical stresses in a transition duct assembly while also providing a transition duct assembly with a natural frequencies outside of critical engine frequencies.
Gas turbine engines operate to produce mechanical work or thrust. Specifically, land-based gas turbine engines typically have a generator coupled thereto for the purposes of generating electricity. A gas turbine engine comprises at least a compressor section having a series of rotating compressor blades. The compressor receives air from an engine inlet. The air passes through the compressor, which causes the pressure of the air to increase. The compressed air is then directed into one or more combustors where fuel is injected into the compressed air and the mixture is ignited. The hot combustion gases are then directed from the combustion section to a turbine section by a transition duct. Depending on the geometry of the gas turbine engine, often times the combustion section is located radially outward of the inlet to the turbine section, and therefore the transition duct must change in at least a radial profile.
A change in the radial profile can cause numerous assembly issues between the combustor and the turbine. Also, such a change in geometry for the transition duct assembly, which is operating at extremely high temperatures can create high thermal and mechanical stresses in the transition duct assembly.
By nature, the transition duct assembly has a natural operating frequency. Also, the gas turbine engine has a natural frequency, and orders of the natural frequency (i.e. 1E, 2E, 3E, etc). When a component has a natural frequency that coincides with an engine natural frequency or order thereof, the component can become dynamically excited and if care is not taken to avoid the crossings of these frequencies, or minimizing the time for the crossing, the component may experience excessive wear or failure due to the excessive vibrations that occur when operating at the natural frequency or order thereof.
Embodiments of the present invention are directed towards a system and method for, among other things, improving movement at the aft frame of a transition duct assembly due to thermal gradients. A mounting system is disclosed that provides for at least lateral movement of the aft frame to adjust due to thermal growth while securing the transition duct assembly at both the inlet and outlet in order to raise the natural frequency of the transition duct assembly outside of the gas turbine engine natural frequency or order thereof.
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 components, combinations of components, steps, or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies.
Referring initially to
It should be understood that the terms “axial”, “radial”, and “circumferential”, as used herein, generally are provided with reference to the turbine 1000 (e.g., a theoretical turbine) connected with the transition duct assembly 100. Accordingly, “axial” generally means with reference to an axis identical to (or parallel with) an axis of the turbine 1000, “radial” generally means along a radius extending from a center rotational axis of the turbine 1000, and “circumferential” generally means along a circumference of a circular frame of the turbine 1000 with which a plurality of transition duct assemblies 100 with exit ends 118 are mounted. Further, the terms “fastener”, “bolt”, and “pin” are used interchangeably herein to denote a component for mechanically coupling adjacent structures together (e.g., through a threaded interconnection, an interference fit, etc).
With continued reference to
In the embodiment shown in
Continuing in reference to
The mounting plate 302 preferably has a pair of axial holes 312 there through matching a pair of axial holes 314 formed in the aft mounting bracket 308. Accordingly, in assembly, the pair of bolts 132 are inserted through the mounting plate axial holes 312 and the aft mounting bracket axial holes 314 to secure the mounting plate 302 and the aft mounting bracket 308 together in abutting relation and mount the aft frame assembly 300 to the turbine 1000 (e.g., via the frame section 1004). As explained in detail below, the remaining portions of the aft frame assembly 300 mount the transition duct exit end 118 with the turbine 1000 through a coupling with the aft mounting bracket 308.
The inner bulkhead assembly 304 and the outer bulkhead assembly 306 are fixed to the aft frame 120 through the retention lugs 124 and 124a. The inner bulkhead assembly 304 includes a first inner bulkhead 316 and a second inner bulkhead 318 positioned on opposite sides of the aft frame retention lugs 124 and 124a. Each of the bulkheads 316 and 318 has a plurality of axial holes 320 there through positioned for alignment with the slots 126 of the aft frame retention lugs 124 and 124a. In assembly, a fastener 322, such as a bolt, is inserted through each axial hole 320 of the bulkheads 316, 318 and through the corresponding slots 126 of the aft frame retention lugs 124 from the exit side of the aft frame assembly 300. A washer 324 and a threaded nut 326 capture each fastener 322 on the forward side of the assembly 300. Additionally, bushings 310 are located on the particular fasteners 322 that extend through the slots 126a in the laterally outermost retention lugs 124a. Each bushing 310 has a second axial length, a second circumferential length, a second radial width, and a through hole for receiving there through the fastener 322. In this configuration, the bushings 310 reside within each slot 126a of the outermost retention lugs 124a and are preferably pressfit into the slots 126a. The bushings 310 are sized such that the first circumferential length of the slots 126a is greater than the second circumferential length of each bushing 310, thereby allowing for relative circumferential movement of each of the outermost retention lugs 124a, and hence aft frame 120, relative to the bushings received therein. This is due to thermal expansion between the retention lugs 124a and respective bulkhead assemblies.
The outer bulkhead assembly 306 has a similar configuration to the inner bulkhead assembly 304, and includes a first outer bulkhead 328 and a second outer bulkhead 330 positioned on opposite sides of the aft frame retention lugs 124 and 124a. Each of the bulkheads 328, 330 likewise has a plurality of axial holes 332 there through positioned for alignment with the slots 126, 126a of the aft frame retention lugs 124, 124a. As with the inner bulkhead assembly 304, assembly is accomplished via placement of fastener 322 through each bulkhead axial hole 332 and through the corresponding slots 126 of the aft frame retention lugs 124 from the exit side of the aft frame assembly 300. A washer 334 and a threaded nut 336 capture each fastener 322 on the forward side of the assembly 300. Additionally, the bushings 310 are used in the same manner in the outer bulkhead assembly 306 as in the inner bulkhead assembly 304.
The interconnection between the outer bulkhead assembly 306 and the aft mounting bracket 308 serves as the coupling point between the aft frame 320 (and thus the transition duct assembly 100) and the turbine frame section 1004. Specifically, the second outer bulkhead 330 is formed with a main body section 338 where the axial holes 332 are disposed, and two or more towers 340 extending radially outward from the main body section 338 generally proximate the circumferential ends of the bulkhead 330. Each tower 340 has a through hole 342 oriented generally perpendicularly to the axial holes 332. The aft mounting bracket 308 is formed with a set of receiving channels 344 sized to receive therein the towers 340 of the bulkhead 330. The channels 344 are each formed between an end flange 346 and a block member 348 of the bracket 308, with both the end flange 346 and block member 348 extending generally in the axial direction. For the embodiment depicted in
With further reference to
The present invention has been described in relation to particular embodiments, which are intended in all respects to be illustrative rather than restrictive. Alternative embodiments will become apparent to those of ordinary skill in the art to which the present invention pertains without departing from its scope.
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. It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and within the scope of the claims.
This application claims priority to U.S. Provisional Application Ser. No. 61/012,636, filed on Dec. 10, 2007.
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Number | Date | Country | |
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61012636 | Dec 2007 | US |