Patent Application
20130167547
The subject matter disclosed herein relates to gas turbines. More particularly, the subject matter relates to an assembly of gas turbine stator components.
In a gas turbine engine, 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. During low load or turndown conditions, it is desirable to reduce fuel flow to the turbine engine to reduce consumption. In some cases, however, the amount of fuel supplied to combustors may be limited by a constant flow of oxygen, wherein a certain amount of fuel is necessary to enable clean burning in the combustor.
According to one aspect of the invention, a gas turbine engine includes a combustor, a fuel nozzle placed in an end of the combustor, and a passage configured to receive an air flow from a compressor discharge casing, wherein the passage directs the air flow into a chamber downstream of the nozzle, wherein a chamber pressure is lower than a compressor discharge casing pressure. The gas turbine engine also includes a flow control device configured to control the air flow from the compressor discharge casing into the passage.
According to another aspect of the invention, a method for flowing air in a turbine engine includes receiving air in a passage from a compressor discharge casing and directing the air from the passage into a combustion chamber downstream of a combustion region in the combustion chamber. The method also includes controlling a flow of the air into the combustion chamber based on an operating condition of the turbine.
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 invention, together with advantages and features, by way of example with reference to the drawings.
In an aspect, the combustor 104 uses liquid and/or gas fuel, such as natural gas or a hydrogen rich synthetic gas, to run the engine. For example, fuel nozzles 110 are in fluid communication with an air supply and a fuel supply 112. The fuel nozzles 110 create an air-fuel mixture, and discharge the air-fuel mixture into the combustor 104, thereby causing a combustion that heats a pressurized gas. The combustor 104 directs the hot pressurized exhaust gas through a transition piece into a turbine nozzle (or “stage one nozzle”) and then a turbine bucket, causing turbine 106 rotation. The rotation of turbine 106 causes the shaft 108 to rotate, thereby compressing the air as it flows into the compressor 102.
In an embodiment, the air received by the fuel nozzles 110 is a portion of the compressed air received from the compressor 102. During a turndown condition, such as during off peak demand, it may be desirable to reduce a fuel flow from the fuel supply 112. In order to meet various emissions and efficiency targets, the amount of air supplied to the fuel nozzles 110 is adjusted based on turbine operating conditions The arrangements discussed below with respect to
As used herein, “downstream” and “upstream” are terms that indicate a direction relative to the flow of working fluid through the turbine. As such, the term “downstream” refers to a direction that generally corresponds to the direction of the flow of working fluid, and the term “upstream” generally refers to the direction that is opposite of the direction of flow of working fluid. The term “radial” refers to movement or position perpendicular to an axis or center line. It may be useful to describe parts that are at differing radial positions with regard to an axis. In this case, if a first component resides closer to the axis than a second component, it may be stated herein that the first component is “radially inward” of the second component. If, on the other hand, the first component resides further from the axis than the second component, it may be stated herein that the first component is “radially outward” or “outboard” of the second component. The term “axial” refers to movement or position parallel to an axis. Finally, the term “circumferential” refers to movement or position around an axis. Although the following discussion primarily focuses on gas turbines, the concepts discussed are not limited to gas turbines and may apply to other rotating machinery, including steam turbines.
The depicted embodiment enables an adjustment of the air 303 supplied to fuel nozzles 304, by changing the amount secondary air 306 flowing through passage 310 and injectors 312. The flow of secondary air 306 from the compressor discharge casing 208 to the combustion chamber 314 is caused by a pressure differential between the regions. Specifically, a pressure in the compressor discharge casing 208, designated as P1, is greater than a pressure P2 in chamber 314. The flow control device 218 controls the amount of secondary air 306 supplied from the compressor discharge casing 208 via the conduit 216. For example, during an elevated demand or high load condition, an increased amount of air 303 is supplied to fuel nozzles 304, while a reduced amount of secondary air 306 flows into combustion chamber 314. Further, during a low load or turndown condition, a reduced amount of air 303 is supplied to the fuel nozzles 304 while an increased amount of secondary air 306 flows into combustion chamber 314. In particular, during the low load condition, the reduced amount of air 303 supplied to the fuel nozzles 304 enables a reduced amount of fuel 305 supplied to the nozzles without adversely affecting combustion. Specifically, the amount of air 303 for combustion with fuel 305 is reduced, thereby reducing carbon monoxide as a combustion byproduct. Further, improved flexibility for various turbine conditions, including combustion during turndown, is achieved by directing secondary air 306 without fuel into chamber 314. In addition, during a high load condition, the flow control device 218 may be restricted to reduce or shut off flow of secondary air 306 to the combustion chamber 314, thereby causing an increased supply of air 303 for combustion with fuel 305. Thus, the adjustable or variable air flow arrangement provides flexibility for operating conditions and improved efficiency.
As depicted, the passage 409 is an annular passage formed between two walls that make up the flow sleeve 402. The annular passage 409 enables air flow in a substantially axial direction in the combustor 400. When the flow control device 407 is open it receives the air 406 at a pressure, P3, that is greater than a pressure, P4, in the combustion chamber, P4, thus causing air flow from the chamber 410 through passage 409 into the combustion chamber 416, downstream of the combustion region 418. Accordingly, when the flow control device 407 is open, an amount of air 403 flowing to the nozzles 404 is reduced, such as during a turndown condition. During turndown (low load) condition, the reduced amount of air 403 for combustion with fuel 405 reduces carbon monoxide production as a combustion byproduct. Further, improved flexibility for various turbine conditions, including combustion during turndown, is achieved by directing secondary air 406 without fuel into combustion chamber 416. In addition, during a high load condition, the flow control device 407 may be restricted to reduce or shut off flow of secondary air 406 to the combustion chamber 416, thereby causing an increased supply of air 403 for combustion with fuel 405. In an embodiment, a position of the flow control device 407 enables flow from the chamber 410, wherein air 406 flow from the chamber 410 reduces an amount of an air flow into a transition piece (not shown) downstream of the combustor 400. The air 403 flow is supplied by the air from the transition piece, and is thus reduced or increased as the amount of air 406 flowing through flow control device 407 is increased or reduced, respectively.
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.
