Patent Application
20120052451
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.
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.
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:
The detailed description explains embodiments of the disclosure together with advantages and features, by way of example with reference to the drawings.
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.
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
With continued reference to
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.
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.
