Patent Application
20140157788
The subject matter disclosed herein relates to gas turbines, and more specifically, to systems and methods for controlling flame stability.
Gas turbine systems generally include a compressor, a combustor, and a turbine. The compressor compresses air from an air intake, and subsequently directs the compressed air to the combustor. In the combustor, the compressed air received from the compressor is mixed with a fuel and is combusted to create combustion gases. The combustion gases are directed into the turbine. In the turbine, the combustion gases pass across turbine blades of the turbine, thereby driving the turbine blades, and a shaft to which the turbine blades are attached, into rotation. The rotation of the shaft may further drive a load, such as an electrical generator, that is coupled to the shaft.
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 one embodiment, a method includes receiving air, fuel, and a diluent in respective air and fuel conduits within a fuel nozzle of a gas turbine system. The method includes directing a mixture of the air and the fuel into a combustion region to produce a flame, and directing the diluent into the combustion region to adjust at least one combustion parameter of the flame.
In a second embodiment, a gas turbine system includes a fuel nozzle. The fuel nozzle includes a first well extending along an axis and defining a first fluid passage. A second wall surrounds the first wall and defines a second fluid passage. A third wall surrounds the second wall and defines a third fluid passage. The first and second fluid passages are configured to collectively direct a flow of air and fuel into a combustion region to produce a flame. The third fluid passage is configured to direct a diluent into the combustion region to adjust a combustion parameter of the flame.
In a third embodiment, a gas turbine system includes a at least one fuel nozzle configured to receive and mix the air with a fuel and a combustor configured to combust a mixture of the air and the fuel into combustion products. The at least one fuel nozzle includes a first wall extending along an axis and defining a first fluid passage, a second wall surrounding the first wall and defining a second fluid passage, and a third wall surrounding the second wall and defining a third fluid passage. The first and second fluid passages are configured to collectively flow the air and the fuel into the combustor to produce a flame. The third fluid passage is configured to direct a diluent into the combustor around the air and the fuel to adjust a combustion parameter of the flame.
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 toward systems and methods to improve flame stability within combustors of gas turbine systems. Typically, a fuel nozzle receives, mixes, and combusts fuel and air, thereby producing a flame. Unfortunately, the flame may be subjected to pressure pulsations and other flame dynamics, which may decrease the efficiency of the gas turbine system. Thus, it is now recognized that undesired flame dynamics may be reduced by modifying the flame location, volume, length, and other combustion parameters of the flame. In a presently contemplated embodiment, a fuel nozzle includes a separate diluent conduit which delivers a diluent (e.g., a non-combustible fluid such as steam, carbon dioxide, or nitrogen) surrounding the flame in order to modify the combustion parameters of the flame. More specifically, the diluent changes the shape and location of the flame by reducing the availability and/or reactivity of the combustible fluids in certain regions of the fuel nozzle. The diluent may also act as a heat sink, thereby abating or delaying the heat release of combustion, which may also reduce the flame dynamics.
Turning now to the figures,
As shown, the diluent and fuel conduits 14 and 16 route respective flows of diluent 26 and fuel 28 into a combustor 30. Notably, the diluent conduit 14 is separate from the fuel conduit 16, which enables the flow of the diluent 26 to be monitored and controlled independently of the flow of the fuel 28. As noted earlier, the diluent 26 may be a non-combustible fluid (e.g., steam or nitrogen) that changes the shape of the combustion flame, a heat sink fluid (e.g., cold air or cold fuel) that reduces or delays the spatial volumetric heat released by the flame, or any combination thereof. In certain embodiments, the composition of the diluent 26 may be adjusted based on certain combustion instabilities associated with operating conditions of the gas turbine system 10 and may vary during the different modes of operation (e.g., start-up or steady-state operation). For example, during start-up of the gas turbine system 10, it may be desirable to purge the combustor 30 using the diluent 26 (e.g., steam) before introducing the fuel 28 to the combustor 30.
The fuel 28 may include a mixture of several components, such as primary fuels (e.g., methane) and fuel additives (e.g., higher hydrocarbons (HHCs) having more carbon atoms than the primary fuel). In certain embodiments, the fuel 28 may also include varying amounts of the diluent 26. That is, the diluent 26 may be supplied to the fuel conduit 16 as well as the diluent conduit 14. As the composition of the fuel 28 generally affects the stability of the flame within the combustor 30, it may be desirable to also control the composition of the fuel 28 (e.g., based on combustion instabilities coupled with operating conditions of the gas turbine system 10, such as flows, temperatures, pressures, combustion dynamics, flame measurements, exhaust composition, or speeds) in order to improve the flame stability. Furthermore, the material supplied to the fuel conduit 16 and the diluent conduit 14 may vary depending on the combustion instabilities and operating mode of the gas turbine system 10. For example, for high-load conditions, it may be desirable to route the fuel 28 through both the diluent conduit 14 and the fuel conduit 16. In general, the flow, pressure, temperature, and/or composition of the diluent 26 and the fuel 28 may be independently increased or decreased based on the detected operating condition. The control logic may vary among embodiments.
As illustrated, the fuel 28 is supplied to the fuel nozzle 12 by a fuel manifold 32 of a fuel supply system 34. Similarly, the diluent 26 is supplied to the fuel nozzle 12 by a diluent supply 36, which, in certain embodiments, may be included within the fuel supply system 34. The fuel supply system 34 and the diluent supply 36 may include, for example, storage tanks, mobile skids, upstream or downstream systems relative to the gas turbine system 10, or any other suitable source of the fuel 28 and the diluent 26.
The fuel nozzle 12 also receives an oxidant, e.g., air 38, supplied by a compressor 40. That is, the air 38 flows from an air intake 42 into the compressor 40, where the rotation of compressor blades 44 compresses and pressurizes the air 38. Within the fuel nozzle 12, the fuel 28 mixes with the air 38 at a ratio suitable for combustion, emissions, fuel consumption, power output, and the like. Thereafter, the mixture of the fuel 28 and the air 38 is combusted into hot combustion products within the combustor 30. These hot combustion products enter a turbine 46 and force turbine blades 48 to rotate, thereby driving a shaft 50 into rotation. The rotating shaft 50 provides the energy for the compressor 40 to compress the air 38. More specifically, the rotating shaft 50 rotates the compressor blades 44 attached to the shaft 50 within the compressor 40, thereby pressurizing the air 38 that is fed to the combustor 30. In addition, the rotating shaft 50 may drive a load 52, such as an electrical generator or any device capable of utilizing the mechanical energy of the shaft 50. After the turbine 46 extracts useful work from the combustion products, the combustion products are discharged to an exhaust 54.
As explained above, the fuel nozzles 12 may include the separate diluent conduits 14 to reduce flame dynamics within the combustor 30. In certain embodiments, a subset of the fuel nozzles 12 may include the separate diluent conduits 14, while another subset of the fuel nozzles 12 do not. For example, the central fuel nozzle 60 (e.g., pilot fuel nozzle) may generally have a greater influence on flame dynamics, and it may be desirable to equip the central fuel nozzle 60 with the separate diluent conduits 14. In other words, the outer fuel nozzles 58, the central fuel nozzle 60, or any combination thereof, may include the diluent conduits 14 to improve the operability (e.g., flame stability) of the gas turbine system 10.
A diluent manifold 68 includes the diluent supply 36 and a diluent pipeline 70 to provide the diluent 26 to the separate diluent conduit 14 of the fuel nozzle 12. As noted above, the diluent 26 may be a non-combustible fluid (e.g., steam or nitrogen) that changes the shape of the combustion flame, a heat sink (e.g., cold air or cold fuel) that reduces or delays the spatial volumetric heat released by the flame, or a combination thereof. In certain embodiments, the composition of the diluent 26 may be based on combustion instabilities and operating mode of the gas turbine system 10. For example, nitrogen may be used to purge the fuel nozzle 12 during startup, and steam may be used to control the shape of the combustion flame during steady-state operation, or vice versa. In embodiments where the diluent 26 is also directed to the fuel conduit 16, the composition of the diluent 26 may vary between the fuel conduit 16 and the diluent conduit 14. Furthermore, the desired flow rate of the diluent 26 may be based on an operating mode of the gas turbine system 10 (e.g., a start-up mode, a steady-state mode, a transient mode, a partial-load mode, a full-load mode, or a full-speed no load mode). For example, higher flow rates of the diluent 26 may be desired with the higher flow rates of the fuel 28 associated with steady-state operation.
Notably, the diluent pipeline 70 is separate from the common pipeline 66 of the fuel manifold 32. As a result, the respective compositions of the fuel 28 and the diluent 26 may be controlled separately from one another. In other words, the illustrated configuration enables the composition of the fuel 28 to be changed without affecting the composition of the diluent 26, and vice versa. To this end, the fuel supply system 34 includes a plurality of control valves 72, 74, and 76 to respectively adjust the composition and/or flow rates of the fuel 28 and the diluent 26. More specifically, the control valves 72 and 74 may selectively enable, throttle, or block of flows of the primary and secondary fuels 62 and 64, respectively, based on a desired composition and/or flow rate of the fuel 28. In a similar manner, the control valve 76 may adjust the flow rate of the diluent 26 to the fuel nozzle 12.
In order to control the operation of fuel supply system 34, a controller 78 is communicatively coupled to the control valves 72, 74, and 76. The controller includes a processor 80 and memory 82 to execute instructions to adjust the composition and/or flow rate of the fuel 28 and the diluent 26 by adjusting the control valves 72, 74, and 76. These instructions may be encoded in software programs that may be executed by the processor 80. Further, these instructions may be stored in a tangible, non-transitory, computer-readable medium, such as the memory 82. The memory 82 may include, for example, random-access memory, read-only memory, hard drives, and/or the like. In certain embodiments, the controller 78 may execute instructions to control the composition and/or flow rate of the fuel 28 and the diluent 26 based on an operating condition of the gas turbine system 10. Furthermore, the flow rate, velocity, temperature, and/or composition of the diluents 26 may be controlled relative to the flow rates of the air 38 and the fuel 28. For example, it may be desirable to increase, keep constant, or decrease the ratio of the diluents 26 to the air 38 and the fuel 28, depending on the combustion instabilities and operating mode of the gas turbine system 10.
As shown, the controller 78 receives input from a sensor 84. The sensor 84 is coupled to the fuel nozzle 12 and detects operating conditions related to combustion of the fuel 28 and the air 38. For example, the sensor 84 may detect a pressure drop across the fuel nozzle 12, a net heat release within the combustor 30, a flame temperature, a flame length, a flame volume, a flame color, a pressure, any other suitable combustion parameter, or any combination thereof. In certain embodiments, the sensor 84 may detect other parameters related to the gas turbine system 10, such as a rotational speed of the shaft 50 or an energy output of the turbine 46. The controller 78 may execute instructions to control the control valves 72, 74, and 76 based on the parameters detected by the sensor 84. For example, the sensor 84 may detect fluctuations in the flame volume as an indication of flame dynamics. The controller 78 may modify the flow rate of the diluent 26 to the diluent conduit 14 of the fuel nozzle by opening the control valve 76 in order to reduce the flame dynamics. As will be appreciated, the controller 78 may also receive feedback from multiple sensors 84 and control the control valves 72, 74, and 76 based on feedback from multiple sensors 84.
The fuel nozzle 12 of
The fuel nozzle 12 also includes a plurality of swirl vanes 104 to mix the fuel 28 with the air 38. In particular, the air 38 may flow axially 18 within the air passage 88 and across the swirl vanes 104. The fuel 28 flows from the fuel passage 92 through the premixing orifices 100 of the swirl vane 104 and enters the air passage 88 to mix with the air 38. As illustrated more clearly in
It should be noted that the embodiments of the fuel nozzles 12 and their respective geometries are not intended to be limiting. For example, the passages 88, 92, and 96 may be interchangeable in certain embodiments. Indeed, the disclosed techniques may be applied to a variety of fuel nozzle designs, all of which fall within the scope and spirit of the present disclosure.
Technical effects of the disclosed embodiments include systems and methods to improve flame stability within the combustor 30 of the gas turbine system 10. In particular, the fuel nozzle 12 is equipped with the separate diluent and fuel conduits 14 and 16 to adjust various characteristics of the combustion flame 102. More specifically, the diluent 28 may change the shape and location of the flame 102 by reducing the availability and/or reactivity of the combustible fluids (e.g., the air 38 and the fuel 28) in certain regions of the fuel nozzle 12. Accordingly, the diluent 26 may behave as a heat sink and may abate or delay the heat release of combustion, thereby reducing flame dynamics and improving the efficiency of the gas turbine system 10.
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.
