Patent Application
20120291447
The present invention generally involves a combustor nozzle and a method for supplying fuel to a combustor. In particular embodiments of the present invention, the combustor nozzle may supply liquid and emulsified fuel to the combustor.
Combustors are commonly used in industrial and commercial operations to ignite fuel to produce combustion gases having a high temperature and pressure. For example, an industrial gas turbine may include one or more combustors to generate power or thrust. A typical commercial gas turbine used to generate electrical power may include an axial compressor at the front, one or more combustors around the middle, and a turbine at the rear. Ambient air may be supplied to the compressor, and rotating blades and stationary vanes in the compressor progressively impart kinetic energy to the working fluid (air) to produce a compressed working fluid at a highly energized state. The compressed working fluid exits the compressor and flows through one or more nozzles in each combustor where the compressed working fluid mixes with fuel and ignites to generate combustion gases having a high temperature and pressure. The combustion gases expand in the turbine to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.
The fuel supplied to the combustor may be a liquid fuel, a gaseous fuel, or a combination of liquid and gaseous fuels. If the liquid and/or gaseous fuel is not evenly mixed with the compressed working fluid prior to combustion, localized hot spots may form in the combustor. The localized hot spots may increase the production of nitrous oxides in the fuel rich regions, while the fuel lean regions may increase the production of carbon monoxide and unburned hydrocarbons, all of which are undesirable exhaust emissions. In addition, the fuel rich regions may increase the chance for the flame in the combustor to flash back into the nozzles and/or become attached inside the nozzles which may damage the nozzles. Although flame flash back and flame holding may occur with any fuel, they occur more readily with high reactive fuels, such as hydrogen, that have a higher burning rate and a wider flammability range.
A variety of techniques exist to allow higher operating combustor temperatures while minimizing undesirable exhaust emissions, flash back, and flame holding. Many of these techniques seek to reduce localized hot spots to reduce the production of undesirable emissions and/or reduce low flow zones to prevent or reduce the occurrence of flash back or flame holding. For example, continuous improvements in nozzle designs result in more uniform mixing of the fuel and compressed working fluid prior to combustion to reduce or prevent localized hot spots from forming in the combustor. Alternately, or in addition, nozzles have been designed to ensure a minimum flow rate of fuel and/or compressed working fluid through the nozzle to cool the nozzle surfaces and/or prevent the combustor flame from flashing back into the nozzle. In still further embodiments, water may be added to the fuel to produce an emulsified fuel, and the nozzle may mix the emulsified fuel with the compressed working fluid prior to combustion to reduce the peak flame temperature, and thus nitrous oxide production, in the combustor. However, the emulsified fuel, if not adequately dispersed, may result in flame instability and/or increased undesirable exhaust emissions. Therefore, continued improvements in the combustor nozzle designs and methods for supplying fuel to the combustor would be useful to improve combustor efficiency, reduce undesirable emissions, and/or prevent flash back and flame holding events.
Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.
One embodiment of the present invention is a combustor nozzle that includes a center body and a first fuel passage inside the center body, wherein the first fuel passage terminates at a first fuel port. A second fuel passage inside the center body and circumferentially surrounding at least a portion of the first fuel passage terminates at a plurality of second fuel ports radially surrounding the first fuel port. A first diluent passage inside the center body and circumferentially surrounding at least a portion of the second fuel passage terminates at a first diluent outlet radially surrounding the plurality of second fuel ports. A shroud circumferentially surrounds at least a portion of the center body to define a passage between the center body and the shroud. A plurality of diluent ports through the shroud provide fluid communication through the shroud to the first diluent passage. A second diluent passage radially disposed between the first diluent passage and the second fuel passage terminates at a second diluent outlet radially inward from the first diluent outlet.
Another embodiment of the present invention is a combustor nozzle that includes a first liquid fuel passage that terminates at a first fuel port and a second liquid fuel passage circumferentially surrounding at least a portion of the first liquid fuel passage that terminates at a plurality of second fuel ports radially surrounding the first fuel port. A first diluent passage surrounding at least a portion of the second liquid fuel passage terminates at a first diluent outlet radially surrounding the plurality of second fuel ports, and a second diluent passage radially disposed between the first diluent passage and the second fuel passage terminates at a second diluent outlet between the first diluent outlet and the plurality of second fuel ports. A third diluent passage surrounds at least a portion of the first and second diluent passages.
Embodiments of the present invention may also include a method for supplying fuel to a combustor that includes flowing a liquid fuel through a first fuel passage in a center body and flowing an emulsified liquid fuel through a second fuel passage in the center body, wherein the second fuel passage surrounds at least a portion of the first fuel passage. The method further includes flowing a first diluent through a shroud surrounding the second fuel passage to a first diluent passage surrounding at least a portion of the second fuel passage, wherein the first diluent passage is inside the center body and flowing a second diluent through a second diluent passage radially disposed between the first diluent passage and the second fuel passage.
Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.
A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:
Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention.
Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Various embodiments of the present invention provide a combustor nozzle and a method for supplying fuel to a combustor. In particular embodiments of the present invention, the combustor nozzle may inject a diluent proximate to a liquid fuel and/or emulsified liquid fuel to enhance mixing and/or evaporation of the fuel prior to combustion. It is anticipated that the enhanced mixing and/or evaporation of the fuel prior to combustion will reduce the production of undesirable emissions. In addition, it is anticipated that the injection of the diluent proximate to the liquid fuel and/or emulsified liquid fuel will reduce or prevent flash back or flame holding events. Although described generally in the context of a combustor nozzle incorporated into a combustor of a gas turbine, embodiments of the present invention may be applied to any combustor and are not limited to a gas turbine combustor unless specifically recited in the claims.
An impingement sleeve 28 with flow holes 30 may surround the transition piece 24 to define an annular passage 32 between the impingement sleeve 28 and the transition piece 24. The compressed working fluid may pass through the flow holes 30 in the impingement sleeve 28 to flow through the annular passage 32 to provide convective cooling to the transition piece 24 and liner 20. When the compressed working fluid reaches the end cover 18, the compressed working fluid reverses direction to flow through the one or more nozzles 14 where it mixes with fuel before igniting in the combustion chamber 22 to produce combustion gases having a high temperature and pressure.
As shown in
The first and second diluent passages 64, 66 may similarly extend axially inside the center body 40, with the second diluent passage 66 radially disposed between the first diluent passage 64 and the first and/or second fuel passages 54, 56. As shown in
The first diluent passage 64 may similarly terminate at a first diluent outlet 78, and the second diluent passage 66 may terminate at a second diluent outlet 80. The first diluent outlet 78 may be disposed radially outward from the first and second fuel ports 72, 74, and the first diluent passage 64 may include a plurality of diluent swirler vanes 82 proximate to the first diluent outlet 78 to impart a radial swirl to the diluent exiting the first diluent outlet 78. The second diluent outlet 80 may be disposed radially between the first diluent outlet and the second fuel ports 74 so that the second diluent outlet 80 circumferentially surrounds the first and second fuel ports 72, 74 proximate to the downstream surface 70 of the center body 40. In addition, the second diluent passage 66 may include a plurality of slots 84 angled with respect to the axial centerline 46 to impart radial swirl to the diluent exiting the second diluent outlet 80. The swirl created by the diluent swirler vanes 82 in the first diluent passage 64 and the slots 84 in the second diluent passage 66 may be in the same direction or opposite directions, depending on the particular embodiment.
The particular arrangement and orientation of the first and second fuel ports 72, 74 and first and second diluent outlets 78, 80 enhances mixing between the liquid and/or emulsified fuel flowing through the fuel ports 72, 74 and the diluent flowing through the diluent outlets 78, 80. Specifically, the diluent exiting the second diluent outlet 80 impacts and mixes with the fuel, which may be emulsified, exiting the second fuel outlets 74 to enhance mixing and/or evaporation of the fuel. In addition, the compressed working fluid flowing between the passage 44 between the shroud 42 and the center body 40, also referred to as a third diluent passage 44, interacts with the fuel and diluent flowing through the first and second fuel ports 72, 74 and first and second diluent outlets 78,80 to further enhance mixing and evaporation of the fuel prior to combustion.
The enhanced mixing and evaporation provided by the first, second, and third diluent passages 64, 66, 44 thus allows a reduced amount of water or steam to be added to the emulsified fuel exiting the second fuel port 74 while still providing the same benefits. Specifically, the diluent flowing through the first, second, and third diluent passages 64, 66, 44 enhances dispersal and evaporation of the emulsified fuel without requiring additional swirling of the emulsified fuel which tends to separate the heavier fuel from the lighter water or steam emulsifier. As a result, the reduced water or steam in the emulsified fuel allows combustion of a leaner fuel mixture while still achieving a desired reduction in flame temperature and undesirable exhaust emissions such as nitrous oxides, carbon monoxide, and unburned hydrocarbons. In addition, the enhanced mixing and evaporation of the emulsified fuel results in less wetting of the liner 20 by fuel, water, or steam, increasing the durability of the liner 20.
The various embodiments of the system shown and described with respect to
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 include 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.
