Patent Application
20090145983
The present invention relates to gas turbine engines. More particularly, embodiments of the present invention relate to an apparatus for reducing thermal growth differential within a fuel nozzle of a gas turbine combustor.
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. There are a number of issues that affect the overall performance and durability of the engine components, especially the combustion section. By nature, the combustion process creates varying pressure oscillations and dynamics that can result in significant wear to the combustion hardware. Specifically, the pressure oscillations can cause mating hardware to vibrate and move relative to one another. Excessive combustion dynamics can cause premature wear of mating hardware such that the hardware must be repaired or replaced.
Gas turbine combustors can have multiple fuel circuits, depending on the quantity and location of the fuel nozzles as well as combustor operating conditions. These fuel circuits and the fuel nozzles that are in fluid communication with the fuel circuits can operate at different times and at different flow rates. Since the fuel nozzles are positioned in close proximity to a flamefront in the combustor, the fuel nozzles are exposed to extremely high temperatures. However, the fuel nozzles carry a fuel having a temperature significantly less than the operating environment, and as a result, the fuel nozzle experiences significant variations in temperature.
The invention is defined by the claims below, not by this Summary, which is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. Embodiments of the present invention are directed towards a system and method for, among other things, minimizing thermal growth within a fuel nozzle so as to reduce thermal stress levels in the fuel nozzle.
The present invention provides embodiments for a fuel nozzle configuration for a gas turbine combustor in which the fuel nozzle receives a heated fluid to elevate the operating temperature of the fuel nozzle so as to reduce the differences in thermal growth of the various fuel nozzle components and reduce thermal stress within the fuel nozzle. In an embodiment of the present invention a fuel nozzle is disclosed comprising an inner tubular member having a centermost passage, an intermediate tubular member surrounding the inner tubular member and forming a secondary passage therebetween, and an outer tubular member surrounding the intermediate tubular member and forming an outer passage. A plurality of injectors extend radially outward from the outer passage for injecting a fuel supply to the combustor from the outer passage while a base end comprises a plurality of feed holes that direct a supply of heating fluid to the secondary passageway. This heating fluid elevates the temperature of the intermediate tubular member to reduce thermal mismatch in the tube between the outer passage and secondary passage. In this embodiment, each of the tubular members are generally cylindrical, except the intermediate tubular member includes a corrugated bellows portion that is used to help compensate for movement caused by thermal growth.
In an additional embodiment, a fuel nozzle is disclosed comprising an inner tubular member having a centermost passage, an intermediate tubular member surrounding the inner tubular member and forming a secondary passage therebetween, and an outer tubular member surrounding the intermediate tubular member and forming an outer passage. A plurality of injectors extend radially outward from the outer passage for injecting a fuel supply to the combustor from the outer passage while a base end comprises a plurality of feed holes that direct a supply of heating fluid to the secondary passageway to elevate the temperature of the intermediate tubular member to reduce thermal mismatch in the tube between the outer passage and secondary passage. In this embodiment, each of the tubular members are generally cylindrical. In a variation of this embodiment, a shield is placed between the intermediate tubular member and the outer tubular member along a portion of the intermediate tubular member so as to provide a thermal shield to the intermediate tubular member.
In yet another embodiment of the present invention, a fuel nozzle is disclosed comprising a solid inner tubular member having a centermost passage and a solid outer tubular member surrounding the inner tubular member and forming an outer passage. A plurality of injectors extend radially outward from the outer passage for injecting a fuel supply from the outer passage to a combustor, while a base end comprises a plurality of feed holes that direct a supply of heating fluid to the centermost passageway to elevate the temperature of the inner tubular member to reduce thermal differential in the tube between the outer passage and the centermost passage.
In a further embodiment, a gas turbine combustor is provided comprising a combustion liner, a cap assembly, and an end cover having a plurality of fuel nozzles that have been previously disclosed. The end cover comprises a plurality of fuel nozzles that extend through openings in the cap assembly such that fuel supplied to the fuel nozzles is injected into the combustor for mixing with compressed air for combustion. Multiple embodiments of the combustor are disclosed in which different embodiments of the fuel nozzle, as previously disclosed, are used. A heating fluid, such as compressed air, is supplied to each of the fuel nozzles through feed holes in each fuel nozzle base. The compressed air elevates the operating temperature of at least one passageway of the fuel nozzle to reduce the thermal gradients in the fuel nozzle and lower thermal stresses caused by large thermal gradients.
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 or combinations of components similar to the ones described in this document, in conjunction with other present or future technologies.
Referring initially to
Located radially outward of and surrounding the intermediate tubular member 106 is an outer tubular member 114. The outer tubular member 114 is positioned such that an outer passage 116 is formed between the outer tubular member 114 and the intermediate tubular member 106. Extending radially outward from the outer passage 116 and therefore in fluid communication with the outer passage 116 are a plurality of injectors 118. These injectors 118 serve to inject a flow of fuel from the outer passage 116 into a combustor, which will be explained in further detail below.
Coupled to the intermediate tubular member 106 and outer tubular member 114 is a base 120. The base 120 provides a location at which the fuel nozzle 100 is mounted to a fuel source, as will be discussed in further details below. For the embodiment depicted in
It has been determined that the level of thermal benefit achieved by supplying a heated fluid to the secondary passage is also dependent on the geometry of the passageways. For example, for the fuel nozzle 100 depicted in
Referring now to
Located radially outward of and surrounding the intermediate tubular member 306 is an outer tubular member 314. The outer tubular member 314 is positioned such that an outer passage 316 is formed between the outer tubular member 314 and the intermediate tubular member 306. Extending radially outward from the outer passage 316 and therefore in fluid communication with the outer passage 316 are a plurality of injectors 318. These injectors 318 serve to inject a flow of fuel from the outer passage 316 into a combustor, which will be explained in further detail below.
Coupled to the intermediate tubular member 306 and outer tubular member 314 is a base 320. The base 320 provides a location at which the fuel nozzle 300 is mounted to a fuel source, as will be discussed in further details below. For the embodiment depicted in
It has been determined that the level of thermal benefit achieved by supplying a heated fluid to the secondary passage is also dependent on the geometry of the passageways. For example for the fuel nozzle 300 depicted in
An alternate configuration of the fuel nozzle 300 is depicted in
An objective of the shield 350 is to effectively insulate fuel in the outer passage 316 from the intermediate tubular member 306 to maximize the temperature of the intermediate tubular member and its thermal growth. This will effectively minimize the relative thermal growth between the outer and intermediate tubular members. A similar effect can also be achieved by enhancing the heat transfer on a side of the intermediate tubular member 306 exposed to the heated fluid through the use of trip strips, surface roughening, or other means, with the goal being to maximize thermal growth of the intermediate tubular member 306 and minimize relative thermal displacement between the tubular members.
Referring now to
Extending radially outward from the outer passage 508 are a plurality of injectors 510. These injectors 510 are in fluid communication with the outer passage 508 and serve to inject a fuel into a combustor, as will be described in more detail below. Coupled to each of the tubular members 502 and 506 is a base 512 that supplies a fuel to the outer passage 508 through one or more passages 514. In an embodiment of the fuel nozzle 500, the base 512 also has a plurality of feed holes 516 that are oriented at an angle relative to the centerline A-A. These feed holes 516 receive a heated fluid, such as compressed air, and direct the heated fluid to the centermost passage 504 so as to elevate the temperature of the inner tubular member 502. Raising the temperature of the inner tubular member 502 reduces the thermal differences between components of the fuel nozzle 500, which thereby reduces thermal stresses in the fuel nozzle 500.
It has been determined that the level of thermal benefit achieved by supplying a heated fluid to the centermost passage 504 is also impacted by the geometry of the passageways of the fuel nozzle 500. For example, it has been determined that in order to provide the benefits discussed above in a nozzle having a smaller diameter of the outer tubular member 506, such as that shown in
Referring now to
Positioned adjacent to the cap assembly 704 is an end cover 710, which has a plurality of fuel nozzles fixed to the end cover 710, with each fuel nozzle corresponding to one of the openings 706 and 708 of the cap assembly. For example, referring to
Although the fuel nozzles 300 and 500 can be used in a variety of combustors, they are depicted for illustrative purposes in a single stage combustor which uses a single fuel nozzle 500 along a center axis B-B of the combustor 700 and a plurality of fuel nozzles 300 in an annular array about the single fuel nozzle 500. Depending on the mode of operation, various fuel nozzles can be flowing fuel so as to minimize the emissions levels and combustor noise, depending on the engine operating conditions. For example, in one operating condition, two or more of the fuel nozzles 300 simultaneously inject a fuel into the combustion liner 702 while fuel is restricted to the fuel nozzle 500. However, in an alternate operating condition, such as during start-up of the engine two or more of the fuel nozzles 300 and the fuel nozzle 500 located along the center axis of the combustor all inject a fuel into the combustion liner 702.
In operation, compressed air is directed along the outside of the combustion liner 702 and travels towards the end cover 710. A majority of the compressed air is turned into the combustion liner 702 by the end cover 710 in conjunction with the cap assembly 704 and is directed through the swirlers of the fuel nozzles 300 and 500 where the air mixes with fuel being injected by the fuel nozzles 300 and 500. However, a portion of the air enters the feed holes 324 and 516 of the fuel nozzles 300 and 500, as previously discussed, in order to raise the temperature of a fuel nozzle internal passageway to reduce thermal growth differences that occurs between adjacent parts of the fuel nozzle. As a result thermal stresses within the fuel nozzles 300 and 500 are lowered.
In yet another alternate embodiment,
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.
