Patent Application
20120111013
The subject matter disclosed herein relates to a fuel nozzle assembly with an improved air flow design.
A gas turbine engine combusts a mixture of fuel and air to generate hot combustion gases, which in turn drive one or more turbines. In particular, the hot combustion gases force turbine blades to rotate, thereby driving a shaft to rotate one or more loads, e.g., an electrical generator. The gas turbine engine includes a fuel nozzle to inject fuel and air into a combustor. In certain combustors, the fuel nozzle receives an air flow at an upstream entrance, wherein the air flow turns from an upstream direction outside the fuel nozzle to a downstream direction inside the fuel nozzle. Unfortunately, the sharp turn at the upstream entrance causes a flow non-uniformity, which can create a low velocity or recirculation zone. In turn, the flow non-uniformity can cause non-uniform mixing of the air flow with fuel and/or a potential for flame-holding.
Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.
In a first embodiment, a system includes a turbine fuel nozzle. The turbine fuel nozzle includes a hub, multiple vanes extending radially outward from the hub, a shroud disposed about the hub and the multiple vanes, an air flow path extending between the hub and the shroud in a downstream direction toward an outlet region of the turbine fuel nozzle, a fuel flow path extending to multiple fuel ports along the air flow path, and a converging-diverging section disposed along the air flow path upstream from the multiple vanes and the multiple fuel ports.
In a second embodiment, a system includes a fuel nozzle assembly. The fuel nozzle assembly includes a hub, a shroud disposed about the hub, a flow sleeve disposed about the shroud, and an air flow path extending between the flow sleeve and the shroud in an upstream direction toward an opening region between the shroud and the hub, wherein the air flow path extends between the hub and the shroud in a downstream direction from the opening region toward an outlet region of the fuel nozzle assembly. The fuel nozzle assembly also includes a fuel flow path extending to at least one fuel port along the air flow path, and a flow guide disposed along the air flow path in the opening region, wherein the flow guide includes a first a guide portion configured to guide an air flow radially outward from the hub toward the shroud.
In a third embodiment, a system includes a turbine engine and a fuel nozzle assembly coupled to the turbine engine. The fuel nozzle assembly includes a flow sleeve including an upstream air flow and multiple fuel nozzles disposed in the flow sleeve. Each fuel nozzle includes a downstream air flow path, and a flow guide configured to direct an air flow toward a low velocity region adjacent a turn between the upstream air flow path and the downstream air flow path.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
The present disclosure is directed to systems for improving the flow of air in a fuel nozzle assembly to eliminate flow deficit regions at or near the entrances to one or more fuel nozzles, thereby reducing flow non-uniformity, pressure drops, and flame-holding. As air enters the fuel nozzle assembly, the flow of air sharply turns from an upstream direction to a downstream direction at or near the entrance to the fuel nozzle. Instead of turning sharply from the upstream direction to the downstream direction, the air flow tends to follow the path of least resistance creating a non-uniform flow or recirculation zone. The recirculation zone results in a pressure drop as well as flow deficits in one or more vane sectors downstream in a premixing passage of the fuel nozzle. The air continues to flow downstream through the premixing passage into swirl vanes which rotate the air flow. Each swirl vane contains one or more fuel ports for injecting fuel into the air flow. Upstream of the swirl vanes are regions of low velocity which may lead to flame-holding.
Embodiments of the present disclosure provide a system that includes a fuel nozzle with a flow guide (e.g., converging-diverging section) that improves flow uniformity. For example, the flow guide (e.g., converging-diverging section) is disposed along the air flow path upstream from the plurality of vanes and the plurality of fuel ports. In certain embodiments, the fuel nozzle may include a shroud (e.g., annular shroud) disposed about a hub (e.g., annular hub) to define an air flow path (e.g., annular air flow path). The flow guide and/or converging-diverging section is disposed in the air flow path at or downstream from an upstream entrance of the fuel nozzle, i.e., between the shroud and the hub. For example, the flow guide includes a first guide portion configured to guide the air flow toward a low velocity region or recirculation zone, e.g., radially outward from the hub toward the shroud. The first guide portion also may converge the air flow passage, and thus may be described as a converging section. The flow guide also may include a second guide portion downstream from the first guide portion, wherein the second guide portion may be angled away from the low velocity or recirculation zone, e.g., from the shroud toward the hub. The second guide may diverge the air flow passage, and thus may be described as a diverging section. In each of the disclosed embodiments, the flow guide substantially reduces or eliminates the flow deficit and reduces pressure drops by redirecting the air flow toward the flow deficit region, while also making the turning of the air flow smoother. The flow guide also improves flow uniformity, and provides sufficient axial velocity of the flow into each downstream vane sector to reduce the possibility of flame-holding.
Turning now to the drawings and referring first to
The outer annular flow passage 45 between the flow sleeve 44 and the cap assembly 46 includes an upstream air flow path 60. In particular, the air flow path 60 extends between the flow sleeve 44 and an outer surface 62 of the shroud 50 in an upstream direction 60 toward an upstream opening region 64 disposed circumferentially about each fuel nozzle 12. For example, the illustrated opening region 64 is disposed between an inner surface 66 of the shroud 50 and the hub 54. Each fuel nozzle 12 within the fuel nozzle assembly 42 includes a downstream air flow path 68 through the inner annular flow passage 53. In particular, the air flow path 68 extends between the hub 54 and the inner surface 66 of the shroud 50. Air enters the fuel nozzle assembly 42 in the upstream direction 60. Upon passing the front plate 48, the air enters a zone 70 and turns (e.g., turning paths 65 and 67) approximately 180 degrees to flow in the downstream direction 68 through the opening region 64 between the hub 54 and shroud 50 of each fuel nozzle 12. The air then flows through the inner annular flow passage 53 between the hub 54 and the shroud 50 toward an outlet region 72 of the fuel nozzle assembly 42. Upon entering the opening regions 64 of the fuel nozzles 12, the air flows downstream to the plurality of vanes 56 to mix with fuel (e.g., fuel ports 58 in vanes 56) along the air flow path 68. A resultant air-fuel mixture 74 is directed toward the outlet region 72 of the fuel nozzle assembly 42 for combustion.
Each fuel nozzle 12 may include any number of vanes 56. For example, each fuel nozzle 12 may include 1 to 20 or 2 to 10 vanes 56, or any number therebetween. Circumferentially about each fuel nozzle 12, the vanes 56 divide the inner annular flow passage 53 into multiple sectors to swirl the air flow and induce mixing of the air with fuel. For example, 10 vanes 56 evenly disposed about the circumference of the fuel nozzle 12 may result in 10 sectors of about 36 degrees each. Air flow entering zone 70 has a tendency of flowing along a path of least resistance, as illustrated by air flow path 65 along an outer surface 63. In other words, the air flow path 65 represents a large radius of a turn of the air flow from the upstream air flow path 60, through the zone 70, toward the downstream air flow path 68. In contrast, a lesser amount of air flow passes through the zone 70 along a small radius of curvature near the front plate 48, as indicated by air flow path 67. The non-uniform flow between the large and small radius of turns (e.g., paths 65 and 67) causes non-uniform flow entering the inner annular flow passage 53 through the opening regions 64. In particular, the air flow may be greater along the hub 54 and lesser along the shroud 50 at the opening regions 64. The fuel nozzles 12 also may receive a non-uniform flow of air from the outer annular flow passage 45 due to different radial distances from the passage 45 to the inner annular flow passage 53 of various fuel nozzles 12. For example, a central fuel nozzle 78 is located at a greater radial distance from the passage 45 then outer fuel nozzles 76. Furthermore, each fuel nozzle 12 may receive more air flow radially closer to the passage 45 and less air flow radially further from the passage 45.
However, the fuel nozzle assembly 42 includes a design to substantially reduce or eliminate the flow deficit regions in the fuel nozzles 12, while smoothly turning the air flow and reducing pressure drops as illustrated in
In the illustrated embodiment, the guide portions 92 and 98 are disposed along the hub 54, while the guide portion 96 is disposed along the shroud 50. However, other embodiments may exclude or rearrange one of more of the guide portions 92, 96, and 98 on the hub 54 and the shroud 50. The guide portions 92 and 96 are disposed upstream from the guide portion 98. In particular, the guide portions 92 and 96 generally converge toward one another (e.g., converge the inner annular flow passage 53) near the opening region 64, thereby defining a converging flow section near the opening region 64. The guide portion 98 contrastingly diverges the inner annular flow passage 53, thereby defining a diverging flow section downstream of the guide portions 92 and 96. As a result, various embodiments of the flow guide 80 may be described as a converging-diverging section 81.
The guide portion 92 is configured to guide the air flow radially outward, as generally indicated by arrow 94, from the hub 54 toward the inner surface 66 of the shroud 50. The radial outward flow 94 provided by the guide portion 92 helps to redistribute the airflow (e.g., large radius airflow path 65) to increase the airflow along the shroud 50 and decrease the airflow along the hub 54, thereby improving uniformity of the airflow in the opening region 64. In particular, the guide portion 92 increases the axial airflow velocity along the shroud 50 and decreases the axial airflow velocity along the hub 54 to create a more uniform axial velocity profile in the passage 53 between the shroud 50 and the hub 54. As illustrated in
The guide portion 96 is configured to guide the air flow radially inward, as generally indicated by arrow 97, around the upstream end of the shroud 50 (e.g., front plate 48). In the illustrated embodiment, the guide portion 96 has a curved annular shape that gradually decreases in angle relative to the axis 108 in the downstream direction. Thus, the guide portion 96 is initially angled more toward the hub 54 at the upstream end portion of the shroud 50, and gradually becomes angled more in the downstream direction (e.g., parallel to the axis 108) toward a downstream end portion 110 of the guide portion 96. In certain embodiments, the guide portion 96 may have a conical shape defined by a generally constant angle relative to the axis 108. In either embodiment, the guide portion 96 generally converges toward the axis 108 and the hub 54 in the downstream direction, thereby converging the passage 53 between the shroud 50 and the hub 54. The guide portion 96 helps to gradually turn the airflow around the upstream end portion of the shroud 50, while also helping to redistribute some of the airflow radially inward toward the hub 54 as indicated by arrow 97. For example, as discussed in further detail below, the guide portion 96 may be angled and positioned to direct some of the airflow radially inward toward the hub 54 at least substantially downstream of the guide portion 92. In this manner, the guide portion 96 helps to improve uniformity of the airflow in the opening region 64. However, as illustrated in
The guide portion 98 is configured to guide the air flow radially inward, as generally indicated by arrow 99, from the shroud 50 toward the hub 54. The radial inward flow 99 provided by the guide portion 98 helps to redistribute the airflow to improve uniformity of the airflow (e.g., more uniform axial velocity profile) in the passage 53 between the shroud 50 and the hub 54. In particular, the guide portion 98 enables the airflow to expand downstream from the guide portions 92 and 96, and specifically flow toward the hub 54. As illustrated in
As mentioned above, the downstream end portion 110 of the guide portion 96 and the downstream end portion 112 of the guide portion 92 are situated to define axial offset 124. The offset 124 may be selected to control the dominance of the guide portion 92 (e.g., outward airflow 120) relative to the guide portion 96 (e.g., inward airflow 123). For example, a greater offset 124 may be used to provide a greater dominance of the airflow 120 provided by the guide portion 92 toward the otherwise low velocity region 122. In contrast, a lesser offset 124 may be used to provide a greater dominance of an airflow 123 provided by the guide portion 96 toward the hub 54. In this manner, the offset 124 may be selected to provide a suitable balance of the outward airflow 120 and the inward airflow 123 to provide a substantially uniform airflow profile across the passage 53.
Along the offset 124, the flow guide 80 includes a guide portion 119 that generally diverges relative to the axis 108 of the fuel nozzle 12. In the illustrated embodiment, the guide portion 119 extends from the downstream end portion 110 of the guide portion 96, and extends partially along the guide portions 92 and 98. The guide portion 119 has an annular surface 121 that may be a variable angle annular surface (e.g., curved annular surface) or a constant angle annular surface (e.g., conical surface). In either embodiment, the annular surface 121 generally diverges from the hub 54 and the axis 108, thereby either maintaining or diverging a flow area of the inner annular flow passage 53 between the shroud 50 and the hub 54. For example, the annular surface 121 may be angled to maintain a substantially constant flow area between the guide portions 92 and 119, while diverging (or increasing) the flow area between the guide portions 98 and 119. As illustrated in
As further illustrated in
The flow guide 80 also provides a variable radial gap 126 within the opening region 64, e.g., between the hub 54 and the shroud 50. The variable radial gap 126 decreases and increases in an axial direction 130 along the axis 108 of the fuel nozzle 12. As discussed in further detail below with reference to
As described above, the converging-diverging section 140 operates to smoothly turn, guide, redistribute, and improve uniformity of the airflow through the opening region 64 of the fuel nozzle 12. Particularly, turning air flow, generally indicated by arrows 156, encounters conical wall section 146 which is angled toward the shroud 50. The conical wall section 146 directs the turning air flow 156 radially outward from the hub 54 toward the shroud 50, as generally indicated by arrows 158. Annular wall section 154 is contoured to direct the turning air flow 156 to fill the space downstream of the conical wall section 148. The divergence of the conical wall section 148 enables expansion of the air flow, as generally indicated by arrows 160, in the downstream air flow path 68. The air flow 160 does not separate from the hub 54 and shroud 50 in the downstream air flow path 68. Thus, in conjunction with one another, the wall sections 146, 148, and 154 substantially reduce or eliminate any flow deficit (e.g., low velocity or recirculation region) along the shroud 50 in the opening region 64. In this manner, the wall sections 146, 148, and 154 substantially increase uniformity of the airflow in the axial direction 130 within the opening region 64 upstream of the vanes 54, thereby reducing the possibility of any flame holding.
Similar to the converging-diverging section 81 of
In addition to the offset 124, the flow guide 80 includes the variable radial gap 126 between the hub 54 and the shroud 50. As mentioned above, the variable radial gap 126 increases and decreases in the axial direction 130 along the axis 108 of the fuel nozzle 12. As illustrated in
Alternatively, as illustrated in
Technical effects of the disclosed embodiments include employing an improved air flow design in the fuel nozzle assembly 42. The improved flow design includes employing the flow guide 80 (e.g., converging-diverging sections 81 or 140) to redirect air flow to flow deficient regions. Redirecting the air flow results in uniform air flow in the axial direction both radially across and circumferentially about the fuel nozzle 12. The redirected air flow also results in reducing pressure losses while providing some axial velocity to all of the vane sectors to minimize the occurrence of flame-holding.
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.
