Combustor and method for supplying fuel to a combustor

A combustor (10) includes a cap (16), a liner (20), a transition piece (24), and a combustion chamber (22) located downstream from the cap (16) and defined by the cap and liner. A secondary nozzle (40) circumferentially arranged around the liner (20) or transition piece (24) includes a center body, a fluid passage through the center body, a shroud circumferentially surrounding the center body, and an annular passage between the center body and the shroud. A method for supplying fuel to a combustor (10) includes flowing fuel through a primary nozzle radially disposed in a breech end of the combustor and flowing fuel through a secondary nozzle (40) circumferentially arranged around and passing through at least one of a liner (20) or a transition piece. The secondary nozzle (40) includes a center body, a fluid passage through the center body, a shroud circumferentially surrounding at least a portion of the center body (44), and an annular passage between the center body and the shroud.

FIELD OF THE INVENTION

The present invention generally involves a combustor and method for supplying fuel to the combustor.

BACKGROUND OF THE INVENTION

Commercial gas turbines are known in the art for generating power. A typical gas turbine used to generate electrical power includes 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 into a combustion chamber 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 combustion gases exiting the turbine include varying amounts of nitrous oxides, carbon monoxide, unburned hydrocarbons, and other undesirable emissions, with the actual amount of each emission dependent on design and operating parameters. For example, the design length of the combustor directly effects the amount of time that the fuel-air mixture remains in the combustor. A longer residence time of the fuel-air mixture in the combustor generally increases the nitrous oxide levels, while a shorter residence time of the fuel-air mixture in the combustor generally increases the carbon monoxide and unburned hydrocarbon levels. Similarly, the operating level of the combustor directly influences the emissions content on the combustion gases. Specifically, higher combustion gas temperatures associated with higher power operations generally increase the nitrous oxide levels, while lower combustion gas temperatures associated with lower fuel-air mixtures and/or turndown operations generally increase the carbon monoxide and unburned hydrocarbon levels. Therefore, continued improvements in the combustor designs and methods for supplying fuel to the combustor would be useful to reducing undesirable emissions in the combustion gases.

BRIEF DESCRIPTION OF THE INVENTION

One embodiment of the present invention is a combustor that includes a cap, a liner extending downstream from the cap, and a transition piece extending downstream from the liner. A combustion chamber is located downstream from the cap and at least partially defined by the cap and the liner. A secondary nozzle is circumferentially arranged around at least one of the liner or the transition piece. The secondary nozzle includes a center body that extends from a casing surrounding the combustor through at least one of the liner or the transition piece, a fluid passage through the center body, a shroud circumferentially surrounding at least a portion of the center body, and an annular passage between the center body and the shroud.

Another embodiment of the present invention is a combustor that includes a cap, a primary nozzle radially disposed in the cap, a liner extending downstream from the cap, a combustion chamber downstream from the cap and at least partially defined by the cap and the liner, and a transition piece extending downstream from the liner. A secondary nozzle is circumferentially arranged around and passes through at least one of the liner or the transition piece. The secondary nozzle includes a center body, a fluid passage through the center body, a shroud circumferentially surrounding at least a portion of the center body, and an annular passage between the center body and the shroud.

The present invention may also include a method for supplying fuel to a combustor that includes flowing a first fuel through a primary nozzle radially disposed in a breech end of the combustor and flowing a second fuel through a secondary nozzle circumferentially arranged around and passing through at least one of a liner or a transition piece. The secondary nozzle includes a center body, a fluid passage through the center body, a shroud circumferentially surrounding at least a portion of the center body, and an annular passage between the center body and the shroud.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the present invention include a combustor having primary and secondary nozzles. The primary nozzles may be located at a breech end of the combustor, and the secondary nozzles may be located peripherally around a combustion chamber. The primary and secondary nozzles provide a staged supply of fuel premixed with compressed working fluid to the combustion chamber to optimize the combustion gas temperature and residence time of the fuel in the combustor.

FIG. 1provides a simplified cross-section of an exemplary combustor10, such as may be included in a gas turbine, according to one embodiment of the present invention. A casing12may surround the combustor10to contain the compressed working fluid flowing to the combustor10. As shown, the combustor10may include one or more primary nozzles14radially arranged in the breech end between a cap16and an end cover18. The cap16and a liner20generally surround or define a combustion chamber22located downstream from the primary nozzles14, and a transition piece24located downstream from the liner20connects the combustion chamber22to a turbine inlet26. As used herein, the terms “upstream” and “downstream” refer to the relative location of components in a fluid pathway. For example, component A is upstream from component B if a fluid flows from component A to component B. Conversely, component B is downstream from component A if component B receives a fluid flow from component A.

An impingement sleeve28with flow holes30may surround the transition piece24to define an annular plenum32between the impingement sleeve28and the transition piece24. The compressed working fluid may pass through the flow holes30in the impingement sleeve28to flow through the annular plenum32to provide convective cooling to the transition piece24and/or liner20. When the compressed working fluid reaches the end cover18, the compressed working fluid reverses direction to flow through the primary nozzles14where it mixes with fuel before igniting in the combustion chamber22to produce combustion gases having a high temperature and pressure.

The combustor10further includes one or more secondary nozzles40circumferentially arranged around the combustion chamber22and aligned approximately perpendicular to the primary nozzles14. In the embodiment shown inFIG. 1, the secondary nozzles40provide fluid communication through the transition piece34to the combustion chamber22.FIG. 2provides an enlarged view of one embodiment of the secondary nozzle40shown inFIG. 1. As shown, the secondary nozzle40may connect to a fluid manifold42located outside of the combustor10. The fluid manifold42may supply fuel and/or a diluent through the secondary nozzle40to the combustion chamber22. Possible liquid fuels supplied from the fluid manifold42through the secondary nozzle40may include light and heavy fuel oil, oil slurries, naptha, petroleum, coal tar, crude oil, and gasoline, and possible gaseous fuels supplied by the fluid manifold42through the secondary nozzle40may include blast furnace gas, carbon monoxide, coke oven gas, natural gas, methane, vaporized liquefied natural gas (LNG), hydrogen, syngas, butane, propane, and olefins. Possible diluents supplied from the fluid manifold42through the secondary nozzle40may include water, steam, fuel additives, various inert gases such as nitrogen, and/or various non-flammable gases such as carbon dioxide or combustion exhaust gases. The location of the fluid manifold42outside of the combustor10allows for ambient air to quickly dilute and dissipate any leaking fuel or diluent and facilitates the detection and repair of any leaks that may develop in the fluid manifold42.

As shown most clearly inFIG. 2, the secondary nozzle40generally includes a center body44that defines a fluid passage46that extends from the casing12surrounding the combustor10through the transition piece24. The fluid passage46may terminate at a plurality of ports48that provides fluid communication between the center body42and the combustion chamber22. In particular embodiments, as shown inFIG. 2, the ports48may be angled with respect to an axial centerline50of the fluid passage46to impart swirl to the fluid flowing through the fluid passage46into the combustion chamber22. In this manner, the center body44, fluid passage46, and ports48allow the introduction of fuel and/or diluents through the transition piece24to the combustion chamber22downstream from the primary nozzles14.

The secondary nozzle40may further include a shroud52that circumferentially surrounds at least a portion of the center body44to define an annular passage54between the center body44and the shroud52. The shroud52may further include a bellmouth opening56around at least a portion of the shroud52to facilitate the introduction of the compressed working fluid into and through the secondary nozzle40. Alternately, or in addition, the secondary nozzle40may include one or more swirler vanes58in the annular passage54to impart a tangential swirl to the compressed working fluid flowing through the annular passage54and into the combustion chamber22.

FIG. 3provides a simplified cross-section of a second embodiment of the combustor10, andFIG. 4provides an enlarged view of the secondary nozzle40shown inFIG. 3. The combustor10again includes the casing12, primary nozzles14, cap16, end cover18, liner20, combustion chamber22, transition piece24, and annular plenum32as previously described with respect toFIGS. 1 and 2. The secondary nozzles40are again circumferentially arranged around the combustion chamber22and aligned approximately perpendicular to each primary nozzle14. In addition, the secondary nozzles40again connect to the fluid manifold42located outside of the combustor10so that the fluid manifold42may again supply fuel and/or diluent through the secondary nozzles40to the combustion chamber22. However, in this particular embodiment, the secondary nozzles40provide fluid communication to the combustion chamber22through the liner20.

As shown most clearly inFIG. 4, each secondary nozzle40again generally includes the center body44, fluid passage46, ports48, annular passage54, and swirler vanes58as previously described with respect to the embodiment shown inFIG. 2. However, in the particular embodiment shown inFIG. 4, the shroud52generally extends continuously from the casing12to the liner20. In addition, the shroud52includes a plurality of apertures60that provides fluid communication through the shroud52to the annular passage54. In this manner, compressed working fluid flowing through the annular plenum32may pass through the apertures60into the annular passage54and flow over the swirler vanes58into the combustion chamber22.

FIG. 5provides an enlarged view of an alternate embodiment of the secondary nozzle40shown inFIG. 3. In this particular embodiment, the swirler vanes58present inFIG. 4have been removed, and the apertures60have been angled at least one of azimuthally or radially with respect to the axial centerline50of the fluid passage46. In this manner, the angled apertures60impart a tangential swirl to the compressed working fluid flowing through the annular passage54and into the combustion chamber22.

The various embodiments shown inFIGS. 1-5provide a method for supplying fuel to the combustor10. The method may include flowing a first fuel through the plurality of primary nozzles14radially disposed in the breech end of the combustor10and flowing a second fuel through the plurality of secondary nozzles40circumferentially arranged around and passing through at least one of the liner20or the transition piece24. The first and second fuels may be the same fuel or different fuel, depending on the particular design and operational needs. Each secondary nozzle40generally includes the center body44, the fluid passage46through the center body44, the shroud52circumferentially surrounding at least a portion of the center body44, and the annular passage54between the center body44and the shroud52. In particular embodiments, the method may include flowing the first fuel approximately perpendicular to the second fuel. Alternately, or in addition, the method may include swirling the second fuel through the ports48and/or swirling the compressed working fluid flowing through the annular passage54into the combustion chamber22.

It is anticipated that the various embodiments and methods described herein may provide one or more material and/or operational benefits over existing combustors. For example, the primary and secondary nozzles14,40provide a staged injection of pre-mixed fuel-air mixtures into the combustion chamber22. The staged injection of pre-mixed fuel-air mixtures may allow for more precise control of combustion gas temperatures during both high power operations as well during reduced power or turndown operations. A more precise control of combustion gas temperatures will in turn enhance the ability to reduce or control undesirable emissions produced across a wider range of combustor10operations. In addition, the arrangement of the secondary nozzles40circumferentially around the combustion chamber22allows for the fluid manifold42to be located outside of the combustor10. As a result, leaks from the fluid manifold42outside of the combustor10may be easier to detect and repair, thus reducing and/or preventing harm caused by leaking fuel or diluent inside the combustor10.