Patent Application
20100132364
The present invention relates generally to gas turbine engines and, more particularly, to a detachable burner tube for use with a gas turbine engine.
Known fuel nozzle assemblies mix air and fuel for combustion. A burner tube assembly is the outermost component of at least some known fuel nozzle assemblies and is designed to protect a plurality of internal components within the fuel nozzle assembly while channeling the air/fuel mixture through the fuel nozzle assembly. Within at least some known burner tube assemblies, a plurality of components are welded together along a plurality of seams.
Assembling known burner tube assemblies, specifically the welding process, may be a difficult task. For example, inlet air flow is determined by the burner tube assembly at the time of assembly and is generally inflexible to any subsequent changes. More specifically, to implement a design change to the air flow generally requires replacement of the entire fuel nozzle assembly. In addition, during assembly, any damage to the burner tube assembly itself may require a repair of the entire fuel nozzle assembly. The assembly process is further complicated by the burner tube assembly, which limits access to the internal components of the fuel nozzle assembly, thus making such components difficult to inspect and service.
Within known fuel nozzle assemblies, the burner tube assembly is designed such that the air flow becomes substantially uniform as it flows downstream. During operation, however, the seams created between the components coupled together may create flow anomalies, such as recirculation zones, that may adversely affect the operation of the fuel nozzle assembly. As such, during assembly, each joint requires special attention to prevent flame holding issues wherein trapped fuel and air may automatically ignite. Moreover, some known burner tube assemblies are not coupled to a support flange, and, in such tubes, a first natural bending frequency of the fuel nozzle assembly may be low enough to be excited by rotor speed multiples, thus increasing a risk of part failure due to vibration.
In one aspect, a method for assembling a fuel nozzle for use with a combustion chamber defined within a gas turbine engine is provided. The method includes providing a swirler assembly, providing a burner tube, and coupling the burner tube to a support flange in a detachable manner such that an inner surface of the burner tube circumscribes an outer surface of the swirler assembly during fuel nozzle operation.
In another aspect, a fuel nozzle configured to channel fluid toward a combustion chamber defined within a gas turbine is provided. The fuel nozzle includes a swirler assembly and a burner tube that is coupled to a support flange in a detachable manner such that an inner surface of the burner tube circumscribes an outer surface of the swirler assembly during fuel nozzle operation.
In yet another aspect, a gas turbine engine is provided. The gas turbine engine includes a combustion chamber and a fuel nozzle configured to channel fluid toward the combustion chamber. The fuel nozzle includes a swirler assembly, a burner tube, and a support flange, wherein the burner tube is coupled to the support flange in a detachable manner such that an inner surface of the burner tube circumscribes an outer surface of the swirler assembly during fuel nozzle operation.
The exemplary methods and systems described herein overcome the disadvantages of known fuel nozzle assemblies and provide a fuel nozzle assembly that is simpler to assemble, disassemble, and service in comparison to known fuel nozzle assemblies.
The terms “axial” and “axially” as used in this application refer to directions and orientations extending substantially parallel to a center longitudinal axis of a centerbody of a burner tube assembly. The terms “radial” and “radially” as used in this application refer to directions and orientations extending substantially perpendicular to the center longitudinal axis of the centerbody. The terms “upstream” and “downstream” as used in this application refer to directions and orientations relative to an axial flow direction with respect to the center longitudinal axis of the centerbody.
During operation, air flows through compressor 102 and compressed air is supplied to combustor 104 and, more specifically, to fuel nozzle assembly 106. Fuel is channeled to a combustion region defined within combustor 104, wherein the fuel is mixed with the compressed air and the mixture is ignited. Combustion gases are generated and channeled to turbine 108, wherein gas stream thermal energy is converted to mechanical rotational energy. Turbine 108 is rotatably coupled to, and drives, shaft 110.
During operation, turbine 108 drives compressor 102 via shaft 110 (shown in
In the exemplary embodiment, outer tube 310 is assembled by tightly rolling at least one piece of sheet metal circumferentially about swirler assembly 320. More specifically, outer tube 310 fully circumscribes and is coupled to swirler assembly 320 via welding. Outer tube 310 includes a plurality of perforated openings 330 defined therein. Perforated openings 330 enable air to enter outer tube 310 at its base end proximate to a flange 340.
In the exemplary embodiment, swirler assembly 430 is fabricated from a first material that has a first coefficient of thermal expansion (CTE), and detachable burner tube 410 is fabricated from a second material that has a second CTE different from the first CTE. Moreover, second material is capable of withstanding higher temperatures than the first material due to its proximity to combustor 104 (shown in
In an alternate embodiment, a gap is defined between the inner surface defining the inner diameter of detachable burner tube 410 and the outer surface defining the outer diameter of swirler assembly 430 at both resting and operating temperatures. In such an embodiment, the gap does not substantially affect the operation of fuel nozzle assembly 400. In another alternate embodiment, a heat assisted process is used to expand detachable burner tube 410 enough to couple detachable burner tube 410 about stem 420 and swirler assembly 430.
In the exemplary embodiment, detachable burner tube 410 is capable of securely coupling to and easily uncoupling from flange 440 via a coupling mechanism 450. Coupling mechanism 450 may include any apparatus capable of coupling and decoupling detachable burner tube 410 to and from flange 440 including, but not limited to, a bolted joint and/or a cam-locking mechanism. When detachable burner tube 410 is coupled to flange 440, detachable burner tube 410 provides axial support to fuel nozzle assembly 400. More specifically, flange 440 and coupling mechanism 450 are configured to provide vibration robustness to detachable burner tube 410. In the exemplary embodiment, a plurality of air passage openings 460 circumscribe a base end of detachable burner tube 410 proximate to a flange 440 and are sized and configured to facilitate access to coupling mechanism 450.
Coupling mechanism 450 enables detachable burner tube 410 to be easily interchanged, which facilitates improved serviceability. For example, rather than replacing an entire fuel nozzle assembly 400 when a detachable burner tube 410 is damaged or worn, a detachable burner tube 410 to be replaced can be easily uncoupled and replaced by a new detachable burner tube 410. Coupling mechanism 450 also facilitates accessing internal components within fuel nozzle assembly 400 such as stem 420 and swirler assembly 430 for service, repair, and inspection by uncoupling detachable burner tube 410 and recoupling detachable burner tube 410 as necessary.
Moreover, the flexibility of interchanging detachable burner tube 410 facilitates changing an air flow design of fuel nozzle assembly 400 by replacing a detachable burner tube 410 with any one of a plurality of detachable burner tubes 410 of various air flow designs.
During operation, detachable burner tube 410 channels an air flow within fuel nozzle assembly 400. More specifically, air enters fuel nozzle assembly 400 via air passage openings 460 and is channeled through detachable burner tube 410 to swirler assembly 430. In the exemplary embodiment, detachable burner tube 410 facilitates channeling air flow such that the air flow is substantially uniform upstream of swirler assembly 430. More specifically, an axial length 470, between air passage openings 460 and swirler assembly 430, and a radial length 480, between stem 420 and detachable burner tube 410, facilitate channeling a desired air flow. In one embodiment, lengths 470 and 480 facilitate eliminating a need for air guide vanes within swirler assembly 430.
In the exemplary embodiment, detachable burner tube 510 includes upper and lower tubes 520 and 530 for cost efficiency purposes. More specifically, lower tube 530 is fabricated from a material that is capable of withstanding high temperatures due to its proximity to combustor 104 (shown in
In the exemplary embodiment, swirler assembly 430 is fabricated from a first material that has a first CTE, upper tube 520 is fabricated from a second material that has a second CTE, different from the first CTE. In the exemplary embodiment, the respective materials of swirler assembly 430 and detachable burner tube 510 facilitate ensuring that the inner surface defining the inner diameter of detachable burner tube 510 is positioned against the outer surface defining the outer diameter of swirler assembly 430. In the exemplary embodiment, the respective materials of swirler assembly 430 and upper tube 520 facilitate creating a tight seal, at operating temperature, between upper tube 520 and swirler assembly 430 without inducing excessive strain to upper tube 520 or swirler assembly 430 during fuel nozzle operation. More specifically, upper tube 520 and swirler assembly 430 define a joint that provides a structural stiffness of fuel nozzle assembly 500 that is configured to transmit loads during operation. Moreover, the respective materials of swirler assembly 430 and upper tube 520 also facilitate axially sliding, at resting or room temperature, detachable burner tube 510 about stem 420 towards and away from a flange 440. In the exemplary embodiment, swirler assembly 430 is fabricated from 347 stainless steel, which has a CTE of 9.81e-6 in/in/° F., and upper tube 520 is fabricated from 410 stainless steel, which has a CTE of 6.4e-6 in/in/° F. In another embodiment, the respective materials of swirler assembly 430 and lower tube 530 are selected to facilitate ensuring that the inner surface defining the inner diameter of lower tube 530 is positioned against the outer surface defining the outer diameter of swirler assembly 430 as described above for upper tube 520.
During operation, plurality of perforated openings 540 and baffle plate assembly 550 are positioned downstream from air passage openings 460 to further facilitate channeling a desired air flow within fuel nozzle assembly 500. In one embodiment, baffle plate assembly 550 facilitates channeling a shorter and broader air flow within fuel nozzle assembly 500 than fuel nozzle assembly 400. More specifically, baffle plate assembly 550 enables a configuration of burner tube 510 wherein an axial length 570 is shorter than axial length 470 (shown in
The detachable burner tube described herein facilitates the operation of a gas turbine engine. More specifically, the detachable burner tube described herein simplifies assembly and disassembly of the fuel nozzle and provides vibration robustness, continuity of flow path, and service flexibility. Practice of the methods, apparatus, or systems described or illustrated herein is neither limited to a detachable burner tube nor to gas turbine engines generally. Rather, the methods, apparatus, and systems described or illustrated herein may be utilized independently and separately from other components and/or steps described herein.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
