FUEL NOZZLE AND METHOD FOR SWIRL CONTROL

Abstract

According to one aspect of the disclosure, an apparatus for injecting fuel is provided, where the apparatus includes a cone structure that includes a passage to form a swirl of an air-fuel mixture in a combustion chamber. The apparatus also includes at least one adjustable vane positioned in the passage configured to control the swirl of the air-fuel mixture and control a flame stability.

Description

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to gas turbines. More particularly, the subject matter relates to combustors in gas turbines.

In a gas turbine, a combustor converts chemical energy of a fuel or an air-fuel mixture into thermal energy. The thermal energy is conveyed by a fluid, often air from a compressor, to a turbine where the thermal energy is converted to mechanical energy. Several factors influence the efficiency of the conversion of thermal energy to mechanical energy. The factors may include blade passing frequencies, fuel supply fluctuations, fuel type and reactivity, combustor head-end volume, fuel nozzle design, air-fuel profiles, flame shape, air-fuel mixing, flame holding and flame stabilization. For example, a highly reactive fuel is desirable due to combustion characteristics and/or cost. However, highly reactive fuel can increase incidences of flame holding. Flame stability is influenced by the fuel nozzles as they project the air-fuel mixture into the combustion chamber. Control over flame stability may lead to control of the location of the combustion, where it is desirable to prevent portions of the flame from forming in the fuel nozzle. In addition, flame development in the nozzle can cause inefficient combustion and shorten the life of the nozzle and combustor.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, an apparatus for injecting fuel is provided, where the apparatus includes a cone structure that includes a passage to form a swirl of an air-fuel mixture in a combustion chamber. The apparatus also includes at least one adjustable vane positioned in the passage configured to control the swirl of the air-fuel mixture and control a flame stability.

According to another aspect of the invention, a method for injecting fuel is provided, where the method includes mixing air and fuel in a passage within a cone structure to form an air-fuel mixture and directing the air-fuel mixture from the passage into in a combustion chamber. The method further includes forming a swirl with the air-fuel mixture and adjusting a position of at least one adjustable vane to control a flame stability and control a property of the swirl of the air-fuel mixture.

These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a sectional side view of a portion of an embodiment of a gas turbine engine, including a combustor, fuel nozzles and compressor;

FIG. 2 is a detailed sectional side view of an embodiment of a fuel nozzle;

FIG. 3 is a detailed sectional side view of an embodiment of a fuel nozzle;

FIG. 4 is a cross sectional view of an embodiment of an adjustable vane, as shown in FIG. 2; and

FIG. 5 is a cross sectional view of an embodiment of adjustable vanes and a cone structure, as shown in FIG. 3.

The detailed description explains embodiments of the disclosure together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a sectional side view of a portion of an embodiment of a gas turbine engine 10, including a combustor 100 and compressor 102. The gas turbine engine includes the compressor 102, combustor 100 and a turbine 103, wherein the turbine is depicted schematically. In the turbine engine 10, combustion of an air fuel mixture in the combustor 100 rotates the turbine 103 to generate mechanical energy in the form of rotational output. Rotation of the turbine 103 also compresses air within the compressor 102. Further, the gas turbine engine may include a plurality of compressors 102, combustors 100 and turbines 103.

In an aspect, the combustor 100 uses liquid and/or gas fuel, such as natural gas or a hydrogen rich synthetic gas, to run the engine. For example, fuel nozzles 104 are coupled to a cover plate 105 and intake an air supply 106 and a fuel supply 107. The air supply 106 and fuel supply 107 are in fluid communication with the fuel nozzles 104. The air flow or supply 106 is directed to the fuel nozzles 104 from a discharge plenum 108 and diffuser 109 of the compressor 102. The fuel nozzles 104 mix the fuel supply 107 with the air supply 106 to create an air-fuel mixture, and discharge the air-fuel mixture into the combustor 100. As depicted, air is directed from the diffuser 109 to the discharge plenum 108 and along an annular passage 110 to the fuel nozzles 104. The fuel nozzles 104 direct an air-fuel mixture, shown by arrow 112, into a combustion chamber 114, thereby causing a combustion that creates a hot pressurized exhaust gas 116. The combustor 100 directs the hot pressurized exhaust gas 116 through a transition piece 118 into a turbine nozzle 120, causing turbine 103 rotation.

In an embodiment, the fuel nozzles 104 mix air supply 106 with the fuel supply 107 to create a swirl of the air-fuel mixture that forms a flow 112 into the combustion chamber 114. For example, the fuel nozzles 104 injects an air-fuel mixture into the combustor 114 in a suitable ratio for improved combustion, emissions, fuel consumption, and power output. Properties of the air-fuel mixture and the air-fuel swirl may affect combustion. For example, a fuel nozzle 104 configuration changes a mean swirl radius and/or velocity of the nozzle flow, thereby affecting the location of the flame and reducing incidence of flame holding in the nozzle 104. Flame holding may be described as a flame formation in an undesirable location in the nozzle, wherein the flame causes high temperatures that can damage the nozzle. Flame stability may be described as control over a location and size of a flame in a combustor, wherein a stable flame of a selected size is consistently formed in a selected location in the combustion chamber.

FIG. 2 is a sectional side view of an embodiment of a fuel nozzle 200. The fuel nozzle 200 includes an outer cone 202 and inner cone 204 coupled to a flange 206. A passage 208 for flow of an air-fuel mixture is located between the outer cone 202 and inner cone 204. The outer cone 202 and inner cone 204 are also described as forming a cone structure. Adjustable vanes 210 are positioned within the passage 208 to control a flow of the air-fuel mixture into a conical chamber 211. Gaseous fuel flow 212 is directed along fuel passage 214, where the fuel is injected through inlets 216 and mixed with air from the compressor in passage 208. In an embodiment, the adjustable vanes 210 are configured to control a swirling of the air-fuel mixture as it enters the conical chamber 211, indicated by arrows 218. As depicted, liquid fuel port 220 is located in an upstream portion of the nozzle 200 to direct a stream 222 of liquid fuel to mix with the air-fuel swirl mixture during turbine engine startup.

In one embodiment, the adjustable vanes 210 are axially staged, where the position of one or more of the vanes 210 is adjusted to control an axial flow component of the air-fuel swirl mixture. For example, the axially staged adjustable vanes 210 are airfoil shaped and pivot along a radial axis 223, thereby affecting an axial component of the nozzle flow, indicated by arrow 224, of the air-fuel mixture as it flows 218 into the chamber 211. This is described in detail in FIG. 4. Thus, the position of adjustable vanes 210 and corresponding axial flow components cause a change in the downstream or axial velocity of the nozzle flow 226, thereby reducing flame holding propensity. Accordingly, the axially staged adjustable vanes 210 improve combustion efficiency while reducing wear and tear on the fuel nozzle 200. In addition, the adjustable vanes 210 may be configured to control various properties of the nozzle flow 226, such as swirl mean radius 228, radial flow velocity, axial flow velocity, swirl vortex length and other characteristics that affect combustion. As shown, the swirl mean radius 228 is measured from a nozzle axis 230, where the swirl mean radius 228 is one measure of the overall size of the nozzle vortex. In some embodiments, the swirl mean radius 228 and vortex size affect the air-fuel mixture and the combustion efficiency of the turbine.

With continued reference to FIG. 2, the adjustable vanes 210 are configured to enable use of a highly reactive gaseous fuel by adding an axial flow or velocity component to the air-fuel mixture 226. Specifically, the axially staged adjustable vanes 210 may be configured to add an axial flow component to force the air-fuel mixture in the combustion chamber. Therefore, the adjustable vanes 210 reduce the chances of flame holding or flashback when using highly reactive or volatile fuel. In some embodiments, it is desirable to use a highly reactive fuel, such as those with a high hydrogen content (e.g., H₂) and the higher order paraffins, due to a high flame temperature and related chemical and thermodynamic properties. Accordingly, the fuel nozzles 200 with adjustable vanes 210 are configured to provide flow control of an air-fuel mixture that enables use of a range of fuels in a turbine engine. For example, when a fuel with low reactivity is used in the turbine, at least one adjustable vane 210 is in a neutral position, where no axial flow component is added to the air-fuel mixture. This is desirable because the risk of flame holding and unwanted combustion in the nozzle is be reduced with low reactivity fuel. Further, when a highly reactive fuel is used, the at least one adjustable vane 210 pivots along radial axis 223 in the passage 208 to add an axial flow component to the air-fuel mixture 226, thereby directing the flow into the combustion chamber. In one embodiment, the position of the adjustable vane 210 adds the axial velocity component that causes desirable combustion in the combustion chamber. Accordingly, by pushing or directing the air-fuel mixture 226 into the combustion chamber, the possibility of flame holding in the fuel nozzle 200 is reduced while also increasing flame stability and control over flame stability. The fuel nozzle 200 may contain one or more adjustable vanes 210, which may be of any suitable shape, such as an airfoil, configured to control a fluid flow in a selected direction. In an embodiment, the adjustable vanes 210 are synchronized, where each of vanes 210 are similarly positioned to cause a substantially similar directional component to the fluid flow across the fuel nozzle 200. Alternatively, each adjustable vane 210 is independently moved to cause different fluid flow from selected regions of the passage 208 into the conical chamber 211. In addition, the adjustable vane 210 may be made of any suitable durable and strong material, such as a steel alloy or composite.

FIG. 3 is a sectional side view of another embodiment of a fuel nozzle 300. The fuel nozzle 300 (or “fuel injector”) includes an outer cone 302, inner cone 304 and passage 306. The passage 306 is located between inner cone 302 and outer cone 304 to direct an air-fuel flow into the nozzle 300. As depicted, a center cone 308 is located between the outer cone 302 and inner cone 304, where the components form a cone structure in the nozzle 300. The center cone 308 divides the passage 306 into two passages for at least a portion of the fuel nozzle 300. The outer cone 302, inner cone 304 and center cone 308 are each coupled to a flange 310. Adjustable vanes 312 are positioned between outer cone 302 and center cone 308. Similarly, adjustable vanes 312 are positioned between inner cone 304 and center cone 308. In an embodiment, the adjustable vanes 312 are pivotally coupled to a portion of the cone structure. For example, a first adjustable vane 312 is pivotally coupled to the outer cone 302 and a second adjustable vane 312 is pivotally coupled to the center cone 308, wherein the adjustable vanes 312 are positioned to control an air-fuel mixture as it flows through passage 306. As depicted, the adjustable vanes 312 are coupled to pivot along a tangential axis 313.

In one embodiment, gaseous fuel flow or supply 314 is routed through passages 316 to fuel inlets 318, where the fuel is mixed with air in the passages 306. The adjustable vanes 312 direct an air-fuel mixture 320 into a conical chamber 321 that flows downstream into the combustor chamber. A liquid fuel port 322 is located in an upstream portion of the nozzle 300 to direct a stream 324 of liquid fuel into conical chamber 321 during turbine engine startup. In one embodiment, the air-fuel mixture 320 flows downstream 326, towards the combustor, forming an air-fuel mixture vortex 328. In an embodiment, the adjustable vanes 312 may be referred to as radial adjustable vanes because they control properties of the air-fuel vortex 328, such as a swirl mean radius 330 of the vortex. As depicted, the swirl mean radius 330 is a dimension measured from nozzle axis 332, where the radial adjustable vanes 312 control the swirl mean radius 330 as it flows into the combustor chamber. By controlling the swirl mean radius 330, flame stability is controlled to improve efficiency and reduce wear on fuel nozzles 300 and other components. In addition, by controlling the swirl mean radius 300, the radial adjustable vanes 312 also affect the axial length of the vortex 328. For example, the radial adjustable vanes 312 are positioned to form a vortex 328 with a small swirl mean radius 330 and long axial length of the vortex 328, thereby causing the air-fuel mixture to extend into the combustion chamber. This causes the flame to form in a desired location in the chamber, thereby controlling flame stability. In an embodiment, adjustable vanes 312 also control the axial velocity as the vortex 328 exits the fuel nozzle 300 to influence the size of a recirculation bubble formed in the combustion chamber, where a large recirculation bubble can also affect flame stability.

In embodiments, the radial adjustable vanes 312 are positioned at angles relative to the flow path or the cone structure. For example, a first radial adjustable vane 312 is in an open position allowing unblocked flow into the conical chamber 321, while a second radial adjustable vane 312 is in a closed position completely blocking a flow into the chamber 321. In another embodiment, the positions of the radial adjustable vanes 312 are synchronized. In yet another embodiment, a single radial adjustable vane 312 is positioned in the passage 306 to control a property of the air-fuel swirl. As discussed herein, adjustable vanes 312 may be configured to provide axial and/or tangential flow components to change an axial and/or tangential flow velocity of an air-fuel mixture, thereby improving the air-fuel mixture and controlling the formation and size of the vortex. Further, by controlling parameters of the air-fuel swirl, combustion and flame location are controlled to reduced flame holding and prevent damage to the fuel nozzle 300.

FIG. 4 is a cross sectional view of an embodiment of an adjustable vane 400, taken along line 4-4 of FIG. 2. As depicted, the adjustable guide vane 400 is in the shape of an airfoil and includes a leading edge 402, trailing edge 404 and pivot point 406. The adjustable guide vane moves about the pivot point 406, as shown by arrow 408, where a position of the adjustable guide vane 400 controls a property of the air-fuel swirl in the combustor. An angle 410 of the adjustable guide vane 400, with respect to air-fuel flow 412, may add an axial flow component to the velocity of the air-fuel swirl. In an embodiment, the adjustable guide vane 400 are described as an axial adjustable guide vane or axially staged guide vane that pivots along a radial axis 414 to cause a change in the axial flow component of the air-fuel mixture. In one example, the angle 410 is between 0 and 90 degrees to change a flow component of the air-fuel swirl. In another example, the angle 410 is between 5 and 60 degrees to change or add a flow component to the air-fuel swirl.

FIG. 5 is a cross sectional view of a portion of an embodiment of a fuel nozzle, taken along line 5-5 of FIG. 3. The position of the fuel nozzle includes an outer cone 500, inner cone 502, center cone 504, first adjustable guide vane 506 and second adjustable guide vane 508. The first adjustable guide vane 506 is positioned in a first passage 510 and the second adjustable guide vane 508 is positioned in a second passage 512. In one embodiment, an air-fuel mixture flows through the first passage 510 and second passage 512, as indicated by arrows 514 and 516, respectively. The positions of the first adjustable guide vane 506 and the second adjustable guide vane 508 may be adjusted, as shown by arrows 516 and 518, respectively. The first adjustable vane 506 includes a pivot point 520 to enable pivotal movement 516. Similarly, the second adjustable vane 508 includes a pivot point 522 to enable pivotal movement 518. In embodiments, there are one or more adjustable guide vanes (506, 508) positioned between the outer cone 500 and inner cone 502.

In one embodiment, the adjustable vanes 506 and 508 are referred to as radial adjustable vanes, where the vanes 506 and 508 are configured to control a size and/or mean radius of the air-fuel vortex in the nozzle and combustion chamber by adjusting the position of one or more of the vanes 506 and 508. For example, an angle 524 of the first guide vane 506, relative to an air-fuel flow 526 are adjusted to control a property of the vortex, such as the swirl mean radius. As depicted, the radial guide vanes 506 and 508 are configured to pivot about two tangential axes to enable control of an air-fuel swirl parameter. The one or more tangential axes are substantially parallel to tangents of the circumference of the nozzle cone structures. In an embodiment, the center cone 504 is not to be located along the entire circumference of the conical nozzle and is only located near the passage (510, 512) exits into the conical chamber. For example, the inner cone 502 and outer cone 500 form a single passage for a portion of the nozzle and the passages 510 and 512 are formed in the portion of the nozzle near the passage exits where the center cone 504 structure is located. In other embodiments, the adjustable vanes 506 and 508 control a flow by changing a position or shape of the vanes using a shape memory material, where the shape memory material is configured to change from a first shape to a second shape when an energy is applied to it. For example, adjustable vanes 506 and 508 may include an alloy, such as Nickel Titanium, embedded in a flexible carbon composite, where a current is selectively applied to the alloy to alter a shape or dimension, such as an angle of the vane or chord and/or span of the vanes.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Claims

1. A fuel nozzle comprising:

a cone structure that includes a passage to form a swirl of an air-fuel mixture in a combustion chamber; and

at least one adjustable vane positioned in the passage configured to control the swirl of the air-fuel mixture and control a flame stability.

2. The fuel nozzle of claim 1, wherein the at least one adjustable vane is configured control an axial flow component of the swirl.

3. The fuel nozzle of claim 1, wherein the at least one adjustable vane comprises a plurality of axially staged adjustable vanes.

4. The fuel nozzle of claim 1, wherein the cone structure comprises an inner cone and an outer cone.

5. The fuel nozzle of claim 1, wherein the at least one adjustable vane is configured to control a mean radius of the swirl.

6. The fuel nozzle of claim 1, wherein the cone structure comprises an inner cone, an outer cone and a center cone.

7. The fuel nozzle of claim 1, wherein the at least one adjustable vane comprises a plurality of radial adjustable vanes.

8. A method for injecting fuel, comprising:

mixing air and fuel in a passage within a cone structure to form an air-fuel mixture;

directing the air-fuel mixture from the passage into a combustion chamber;

forming a swirl with the air-fuel mixture; and

adjusting a position of at least one adjustable vane to control a property of the swirl of the air-fuel mixture.

9. The method of claim 8, wherein adjusting a position of at least one adjustable vane comprises reducing flame holding in a fuel nozzle.

10. The method of claim 8, wherein adjusting a position of at least one adjustable vane comprises pivoting the at least one adjustable vane along a radial axis.

11. The method of claim 8, wherein adjusting a position of at least one adjustable vane comprises pivoting the at least one adjustable vane along a tangential axis.

12. The method of claim 8, wherein adjusting a position of at least one adjustable vane controlling a mean radius of the swirl.

13. The method of claim 8, wherein adjusting a position of at least one adjustable vane comprises controlling an axial flow component of the swirl.

14. A combustor, comprising:

a combustion chamber;

an air supply in fluid communication with at least one fuel nozzle positioned in the combustion chamber; and

a fuel supply in fluid communication with the at least one fuel nozzle, wherein the at least one fuel nozzle comprises: a cone structure that includes a passage to form an air-fuel swirl in the combustion chamber; and at least one adjustable vane positioned in the passage configured to control a property of the air-fuel swirl and control a flame stability.

15. The combustor of claim 14, wherein the property of the air-fuel swirl comprises an axial flow component of the air-fuel swirl.

16. The combustor of claim 15, wherein a position of the at least one adjustable vane is configured to reduce flame holding.

17. The combustor of claim 14, wherein the property of the air-fuel swirl comprises a mean radius of the swirl.

18. The combustor of claim 14, wherein the cone structure comprises an inner cone and an outer cone.

19. The combustor of claim 14, wherein the at least one adjustable vane comprises a plurality of axially staged adjustable vanes.

20. The combustor of claim 14, wherein the at least one adjustable vane comprises a plurality of radial adjustable vanes.