Patent Application
20170363294
The present invention generally involves a fuel nozzle assembly for a gas turbine combustor. More specifically, the invention relates to a pilot premix nozzle for a fuel nozzle assembly.
As requirements for gas turbine emissions have become more stringent, one approach to meeting such requirements is to move from diffusion flame combustors to combustors utilizing lean fuel and air mixtures using a fully premixed operations mode to reduce emissions of, for example, NOx and CO. These combustors are generally known in the art as Dry Low NOx (DLN), Dry Low Emissions (DLE) or Lean Pre Mixed (LPM) combustion systems.
Certain DLN type combustors include a plurality of primary fuel nozzles which are annularly arranged about a secondary or center fuel nozzle. The fuel nozzles are circumferentially surrounded by an annular combustion liner. The combustion liner defines an upstream combustion chamber and a downstream combustion chamber of the combustor. The upstream combustion chamber and the downstream combustion chamber may be separated by a throat portion of the combustion liner.
During operation of the combustor, the primary fuel nozzles may provide fuel to the upstream combustion chamber. Depending on the operational mode, the fuel from the primary fuel nozzles may be burned in the upstream combustion chamber or may be premixed with compressed air within the upstream combustion chamber for ignition in the downstream combustion chamber. The secondary fuel nozzle serves several functions in the combustor including supplying fuel and air mixture to the downstream combustion chamber for premixed mode operation, supplying fuel and air for a pilot flame supporting primary nozzle operation and providing transfer fuel for utilization during changes between operation modes.
In certain combustors, the secondary fuel nozzle may include a diffusion pilot nozzle disposed at a downstream end of the secondary fuel nozzle. The diffusion pilot nozzle provides a stream of fuel and air to the second combustion chamber and is employed for anchoring a secondary flame. However, in order to comply with various emissions requirements the fuel flow to the pilot fuel circuit may be reduced. As a result, the reduced fuel flow to the pilot fuel circuit may impact combustion dynamics and/or lean blow out limits.
Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.
One embodiment of the present invention is a pilot premix nozzle. The pilot premix nozzle includes a nozzle body. The nozzle body comprises a forward wall that is axially spaced from an aft wall and an outer band that extends axially between the forward wall and the aft wall. The aft wall includes an inner surface that is axially spaced from an outer surface. An air tube extends coaxially within the nozzle body and terminates at the inner surface of the aft wall. The air tube at least partially defines a cooling air plenum within the nozzle body. A fuel tube extends coaxially within the nozzle body and at least partially circumferentially surrounds the air tube. The fuel tube and the air tube define a fuel inlet plenum therebetween. A fuel distribution plenum is defined within the nozzle body and is in fluid communication with the fuel inlet plenum. The nozzle body also includes a plurality of premix tubes. Each premix tube of the plurality of premix tubes defines a respective premix passage through the nozzle body and includes an inlet defined along the forward wall and an outlet defined along the aft wall of the nozzle body. Each respective premix tube extends helically around the fuel tube within the fuel distribution plenum. One or more of the premix tubes of the plurality of premix tubes is in fluid communication with the fuel distribution plenum.
Another embodiment of the present disclosure is a fuel nozzle assembly. The fuel nozzle assembly includes an outer tube, an inner tube that extends coaxially within the outer tube, an intermediate tube that extends coaxially within the outer tube and that circumferentially surrounds and is radially spaced from the inner tube, and a premix pilot nozzle that is coupled to a downstream end of the outer tube via a nozzle ring. The premix pilot nozzle comprises a nozzle body. The nozzle body includes a forward wall that is axially spaced from an aft wall and an outer band that extends axially between the forward wall and the aft wall. The aft wall includes an inner surface that is axially spaced from an outer surface. An air tube is coupled at one end to the inner tube and extends coaxially within the nozzle body. The air tube terminates at the inner surface of the aft wall and at least partially defines a cooling air plenum within the nozzle body. A fuel tube is coupled at one end to the intermediate tube. The fuel tube extends coaxially within the nozzle body and circumferentially surrounds at least a portion of the air tube. The fuel tube and the air tube define a fuel inlet plenum therebetween. A fuel distribution plenum is defined within the nozzle body and is in fluid communication with the fuel inlet plenum. The nozzle body also includes a plurality of premix tubes. Each premix tube defines a premix passage through the nozzle body and includes a respective inlet that is defined along the forward wall and a respective outlet that is defined along the aft wall. Each premix tube extends helically around the fuel tube within the fuel distribution plenum. One or more of the premix tubes of the plurality of premix tubes is in fluid communication with the fuel distribution plenum.
Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.
A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:
Reference will now be made in detail to present embodiments of the disclosure, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the disclosure.
As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. The term “radially” refers to the relative direction that is substantially perpendicular to an axial centerline of a particular component, and the term “axially” refers to the relative direction that is substantially parallel and/or coaxially aligned to an axial centerline of a particular component.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Each example is provided by way of explanation, not limitation. In fact, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents. Although exemplary embodiments of the present disclosure will be described generally in the context of a fuel nozzle assembly for a land based power generating gas turbine combustor for purposes of illustration, one of ordinary skill in the art will readily appreciate that embodiments of the present disclosure may be applied to any style or type of combustor for a turbomachine and are not limited to combustors or combustion systems for land based power generating gas turbines unless specifically recited in the claims.
Referring to the drawings,
The combustion section 14 may include a plurality of combustors 20 (one of which is illustrated in
During operation of the combustor 20, the primary fuel nozzles 28 may provide fuel to the upstream combustion chamber 34. Depending on the operational mode of the combustor 20, the fuel from the primary fuel nozzles 28 may be burned in the upstream combustion chamber 34 or may be premixed with the compressed air 24 within the upstream combustion chamber 34 for ignition in the downstream combustion chamber 36. The secondary fuel nozzle 30 serves several functions in the combustor 20 including supplying a fuel and air mixture to the downstream combustion chamber 36 for premixed mode operation, supplying fuel and air for a pilot flame which supports primary nozzle operation and providing transfer fuel for utilization during changes between operation modes.
In various embodiments, as shown in
In particular embodiments, the fuel nozzle 100 may include a secondary intermediate tube 116 that extends axially within the outer tube 102 with respect to the axial centerline of the fuel nozzle 100. The secondary intermediate tube 116 circumferentially surrounds at least a portion of the intermediate tube 110 and defines a secondary fuel passage 118 within the outer tube 102. A plurality of fuel pegs 120 may be circumferentially spaced about the outer tube 102. Each fuel peg 120 may extend radially outwardly from the outer tube 102 with respect to the axial centerline of the fuel nozzle 100. One or more of the fuel pegs 120 may include one or more fuel injection orifices 122 which are in fluid communication with the secondary fuel passage 118.
In various embodiments, the fuel nozzle 100 includes a premix pilot nozzle 124. The premix pilot nozzle 124 includes a nozzle body 126 that extends axially through a nozzle ring 128. The nozzle ring 128 may be coupled to the downstream end portion 106 of the outer tube 102. In particular embodiments, the nozzle ring 128 may be formed as a singular or unitary component with the nozzle body 126.
In various embodiments, as shown in
In at least one embodiment, the aft wall 132 defines a plurality of exhaust ports 144. Each exhaust port 144 includes a respective inlet 146 that is defined within or surrounded by the air tube 138 and a respective outlet 148 defined along an outer surface 150 of the aft wall 132. Each exhaust port 144 is in fluid communication with the cooling air plenum 142. As shown in
In various embodiments, as shown in
As shown in
In various embodiments, as shown in
As shown in
In various embodiments, as shown in
In at least one embodiment, as shown in
In at least one embodiment, the nozzle body 126 is formed as a singular body. In other words, the forward wall 130, the aft wall 132, the outer band 134, the air tube 138, the fuel tube 154 and the premix tubes 168 may all be formed from or as a singular body. In at least one embodiment, the nozzle body 126 and the nozzle ring 128 are formed from a singular body. For example, in particular embodiments, the nozzle body 126 with or without the nozzle ring 128 may be formed via an additive manufacturing process. The terms additive manufacturing or additively manufactured as used herein refers to any process which results in a useful, three-dimensional object and includes a step of sequentially forming the shape of the object one layer at a time. Additive manufacturing processes may include three-dimensional printing (3DP) processes, laser-net-shape manufacturing, direct metal laser sintering (DMLS), direct metal laser melting (DMLM), plasma transferred arc, freeform fabrication, etc.
During operation of the premix pilot nozzle 124, as shown collectively in
Compressed air may be routed through the inner tube 108 and into the cooling air plenum 142 defined within the air tube 138 of the nozzle body 126. The compressed air may then flow out of the cooling air plenum 142 via the plurality of exhaust ports 144. The exhaust ports 144 may be formed or angled so as to create a film of the compressed air across the outer surface 150 of the aft wall 132, thereby cooling the and/or providing a protective film across the outer surface 150 of the aft wall 132. The bosses 190 may prevent or block the cooling air from mixing with or otherwise interacting with the flow of premixed fuel and air as it exits the respective outlets 174 of the premix passages 170.
The premix pilot nozzle 124 as shown and described herein, may replace known high temperature and high Emissions diffusion type pilot nozzles which stabilize the flame in the downstream combustion chamber 36 at high temperature but at the expense of emissions. The premix pilot nozzle 124 as shown and described herein may replace known diffusion type premix pilot nozzles with a swirl stabilized premixed pilot nozzle. The premixed pilot nozzle 124 may result in more desirable emissions levels with the same flame stability provided by known diffusion type pilot nozzles while also providing improved dynamics and/or lean blow out limits.
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 include 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.
