Patent Description:
The invention disclosed herein relates to a fuel nozzle for a combustion system.

Gas turbines operate by combusting fuel in a combustion system or a plurality of combustors to create a high-energy combustion gas that passes through a turbine, thereby causing a turbine rotor shaft to rotate. The rotational energy of the rotor shaft may be converted to electrical energy via a generator coupled to the rotor shaft. Each combustor generally includes fuel nozzles that may provide premixing of the fuel and air upstream of the combustion zone, as a means to keep nitrogen oxide (NOx) emissions low.

Gaseous fuels, such as natural gas, often are employed as a combustible fluid in gas turbine engines used to generate electricity. In some instances, it may be desirable for the combustion system to be able to combust liquid fuels, such as distillate oil, with no changes to the combustion hardware. A configuration with both gas and liquid fuel capability is called a "dual fuel" combustion system. In a typical configuration, the liquid fuel injection is provided though cartridges that fit in the center of the gas premixing fuel nozzles.

To provide an operator of the gas turbine with the ability to switch between gas-only operation and dual-fuel operation, conventional fuel nozzles may be installed with blank or dummy cartridges that may be easily replaced with liquid fuel cartridges. These blank cartridges, which are used for gas-only operation, merely fill the space in the center of the fuel nozzle that may eventually be occupied by a liquid fuel cartridge. The blank cartridges are typically purged with air to cool the tips of the cartridges, which face the combustion zone, to keep the tips at an acceptable temperature.

A large portion of gas turbine operators rely primarily on the combustion of gaseous fuels and employ the gas only configuration of the combustion system. During operation the combustion system directs purge flow through or around a tip portion of the blank cartridge. While this purge flow is generally a small fraction of the total flow through the combustor, the purge flow does not participate in the fuel/air premixing prior to combustion and, thus, does not contribute to a reduction in NOx emissions. It is generally desirable and often required by regulations to keep gas turbine NOx emissions at the lowest achievable level.

<CIT> discloses a flame-holding nozzle for a combustion turbine engine. The nozzle includes several elongated sleeves in a substantially-concentric arrangement. The sleeves cooperatively provide distinct passageways for fluids to move through the nozzle. The nozzle includes conduits that advantageously direct fluids to designated regions of the nozzle, allowing fuel and cooling fluid to move within the nozzle without becoming commingled. Portions of the nozzle sleeves are also strategically arranged to transmit fluids in a manner that provides substantially-uniform thermal expansion, thereby eliminating the need for sliding joints or bellows arrangements.

<CIT> relates to a burner system, in particular for a gas turbine, with a main supply channel, debouching into a combustion chamber, for a fuel/air mixture having a swirler and a burner lance which passes through the swirler. To improve the transverse ignition properties between several such burner systems, optionally disposed on the burner chamber, and also to increase the flame stability, the burner lance has, on the combustion chamber side with respect to the swirler exit openings for fuel supplied to its interior or for a fuel-rich fuel/air mixture supplied to, or formed in, its interior.

The herein claimed invention relates to the subject matter set forth in the claims. Aspects and advantages are set forth below in the following description, or may be obvious from the description, or may be learned through practice.

Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments of the invention, and others, upon review of the specification.

A full and enabling disclosure of various embodiments of the invention, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:.

Like or similar designations in the drawings and description have been used to refer to like or similar parts of the disclosure.

The term "radially" refers to the relative direction that is substantially perpendicular to an axial centerline of a particular component, and the term "axially" refers to the relative direction that is substantially parallel and/or coaxially aligned to an axial centerline of a particular component.

Each example is provided by way of explanation, not limitation. In fact, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the scope 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 disclosure covers such modifications and variations as come within the scope of the appended claims.

Although exemplary embodiments of the present invention will be described generally in the context of a fuel nozzle for a land based power generating gas turbine combustor for purposes of illustration, one of ordinary skill in the art will readily appreciate that embodiments of the present invention may be applied to any style or type of combustor for a turbomachine and are not limited to combustors or combustion systems for land based power generating gas turbines unless specifically recited in the claims.

Referring now to the drawings, <FIG> illustrates a schematic diagram of an exemplary gas turbine <NUM>. The gas turbine <NUM> generally includes an inlet section <NUM>, a compressor <NUM> disposed downstream of the inlet section <NUM>, a combustion system <NUM> including at least one combustor <NUM> disposed downstream of the compressor <NUM>, a turbine <NUM> disposed downstream of the combustor <NUM> and an exhaust section <NUM> disposed downstream of the turbine <NUM>. Additionally, the gas turbine <NUM> may include one or more shafts <NUM> that couple the compressor <NUM> to the turbine <NUM>.

During operation, air <NUM> flows through the inlet section <NUM> and into the compressor <NUM> where the air <NUM> is progressively compressed, thus providing compressed air <NUM> to the combustor <NUM>. Fuel <NUM> from a fuel supply <NUM> is injected into the combustor <NUM>, mixed with a portion of the compressed air <NUM> and burned to produce combustion gases <NUM>. The combustion gases <NUM> flow from the combustor <NUM> into the turbine <NUM>, wherein energy (kinetic and/or thermal) is transferred from the combustion gases <NUM> to rotor blades (not shown), thus causing shaft <NUM> to rotate. The mechanical rotational energy may then be used for various purposes such as to power the compressor <NUM> and/or to generate electricity. The combustion gases <NUM> exiting the turbine <NUM> may then be exhausted from the gas turbine <NUM> via the exhaust section <NUM>.

As shown in <FIG>, the combustor <NUM> may be at least partially surrounded by an outer casing <NUM> such as a compressor discharge casing. The outer casing <NUM> may at least partially define a high pressure plenum <NUM> that at least partially surrounds various components of the combustor <NUM>. The high pressure plenum <NUM> may be in fluid communication with the compressor <NUM> (<FIG>) so as to receive the compressed air <NUM> therefrom. An end cover <NUM> may be coupled to the outer casing <NUM>. In particular embodiments, the outer casing <NUM> and the end cover <NUM> may at least partially define a head end volume or portion <NUM> of the combustor <NUM>. In particular embodiments, the head end portion <NUM> is in fluid communication with the high pressure plenum <NUM> and/or the compressor <NUM>. One or more liners or ducts <NUM> may at least partially define a combustion chamber or zone <NUM> for combusting the fuel-air mixture and/or may at least partially define a hot gas path <NUM> through the combustor for directing the combustion gases <NUM> towards an inlet to the turbine <NUM>.

In various embodiments, as shown in <FIG>, the combustor <NUM> includes one or more fuel nozzles <NUM> coupled to the end cover <NUM> and extending towards the combustion chamber <NUM>. Various embodiments of the combustor <NUM> may include different numbers and arrangements fuel nozzles <NUM> and is not limited to any particular number of fuel nozzles unless otherwise specified in the claims. For example, in particular configurations the one or more fuel nozzles <NUM> may include multiple fuel nozzles annularly arranged about a center fuel nozzle.

<FIG> shows an exemplary fuel nozzle <NUM> having a gas-only cartridge <NUM>, according to at least one embodiment of the present invention. In at least one embodiment, the fuel nozzle <NUM> includes a base portion <NUM>, a center body <NUM> having an annular or tube shape, an outer sleeve or burner tube <NUM> that extends circumferentially around at least a portion of the center body <NUM> and a plurality of turning vanes <NUM> that extend between the center body <NUM> and the outer sleeve <NUM>. The turning vanes <NUM> are disposed within a primary premix air passage <NUM> which is defined between the center body <NUM> and the outer sleeve <NUM>. The center body <NUM> may be formed from one or more sleeves or tubes <NUM> coaxially aligned with the base portion <NUM> along a longitudinal axis or axial centerline of the fuel nozzle <NUM>.

An upstream end portion <NUM> of the outer sleeve <NUM> may at least partially define an inlet <NUM> to the primary premix air passage <NUM> and a downstream end portion <NUM> of the outer sleeve <NUM> may at least partially define an outlet <NUM> of the primary premix air passage <NUM>. In at least one embodiment, the inlet <NUM> is in fluid communication with the head end <NUM> (<FIG>) of the combustor <NUM>. The base portion <NUM> may be connected to an inner surface of the end cover <NUM> via mechanical fasteners or by other connecting means. In particular embodiments, the base portion <NUM>, the center body <NUM> and the outer sleeve <NUM> are coaxially aligned along the longitudinal axis of the fuel nozzle <NUM>.

In one embodiment, an inner sleeve <NUM> may extend axially within the base portion <NUM> and/or at least a portion of the center body <NUM> and may at least partially surround a portion of the gas-only cartridge <NUM>. The inner sleeve <NUM> may at least partially define a fuel circuit or passage <NUM> for providing fuel to a plurality of fuel ports <NUM> disposed/defined along one or more of the turning vanes <NUM>. The fuel circuit <NUM> may be in fluid communication with one or more fuel circuits <NUM> defined in the end cover <NUM>. The fuel ports <NUM> are in fluid communication with the primary premix air passage <NUM>. In one embodiment, the fuel circuit <NUM> may be at least partially defined between a portion of the gas-only cartridge <NUM> and the inner sleeve <NUM>.

According to the invention as herein claimd, a tip body <NUM> is disposed at and/or defines a downstream end <NUM> of the center body <NUM>. <FIG> provides an isometric view of the tip body <NUM> according to at least one embodiment of the present disclosure. <FIG> provides a perspective cross sectional view of a portion of the fuel nozzle <NUM> including a portion of the center body <NUM> including the tip body <NUM> and a portion of the gas-only cartridge <NUM> according to at least one embodiment of the present disclosure. As shown in <FIG>, the tip body <NUM> includes an upstream side or surface <NUM> axially spaced from a downstream side or surface <NUM>. The tip body <NUM> defines an opening <NUM> (<FIG>) that extends through the upstream surface <NUM> and the downstream surface <NUM>. As shown in <FIG>, the opening <NUM> may be sized to allow a fuel distribution tip <NUM> of the gas-only cartridge <NUM> to extend at least partially therethrough.

According to the invention as herein claimd, as shown in <FIG>, an inner surface <NUM> of the tip body <NUM> includes and/or defines a plurality of slots, grooves or channels <NUM> annularly arranged about the opening <NUM>. Each channel <NUM> extends through the upstream surface <NUM> and the downstream surface <NUM> of the tip body <NUM> and defines a respective flow path through the tip body <NUM>. The channels <NUM> may have any cross sectional shape and the particular cross sectional shape of the channels <NUM> is not limited to a particular cross sectional shape unless otherwise recited in the claims.

The channels <NUM> may have the same cross sectional shape or may have different cross sectional shapes. In one embodiment, as shown in <FIG>, one or more of the channels <NUM> may have a substantially "U" cross sectional shape. Other cross sectional shapes may include a "C" or horseshoe shape where walls of each channel <NUM> meet or engage with the cartridge past perpendicular. In particular embodiments, as shown in dashed lines of <FIG>, one or more of the channels <NUM> may be angled with respect to the axial centerline of the fuel nozzle <NUM>. In one embodiment, the channels <NUM> may be oriented such as in a helical pattern, so as to impart angular swirl to air and/or a fuel and air mixture flowing through the channels <NUM>. In one embodiment, one or more of the channels <NUM> may be oriented so as direct a flow of fuel-air mixture radially outwardly from the axial centerline towards the outer sleeve <NUM>. In at least one embodiment, the tip body <NUM> may include and or define a plurality of circumferentially spaced cooling passages, as indicated by dashed lines <NUM>, annularly arranged about or radially outwardly from the channels <NUM>. The cooling passages <NUM> may provide for fluid communication through the upstream surface <NUM> and the downstream surface <NUM> of the tip body <NUM>.

<FIG> provides a perspective side view of the gas-only cartridge <NUM> according to at least one embodiment of the present disclosure. The gas-only cartridge <NUM> includes an outer tube <NUM>. The outer tube <NUM> may include a first end <NUM> that is coupled to a base flange <NUM> and a second end <NUM> that connected to and/or that at least partially defines the fuel distribution tip <NUM>. As shown in <FIG>, the base flange <NUM> may be formed to connect to an outer surface of the end cover <NUM> and the outer tube <NUM> may extend through the end cover <NUM> from the base flange <NUM>. As shown in <FIG>, when installed into the fuel nozzle <NUM>, the outer tube <NUM> of the gas-only cartridge <NUM> and the center body <NUM> at least partially define a secondary premix air passage <NUM> therebetween.

As shown in <FIG> and <FIG>, the gas-only cartridge <NUM> further includes an inner tube <NUM> that extends axially within the outer tube <NUM>. The outer tube <NUM> is radially spaced from the inner tube <NUM> so as to define a fuel passage <NUM> therebetween. In particular embodiments the inner tube <NUM> defines an air passage <NUM> within the gas-only cartridge <NUM>.

<FIG> provides an enlarged cross sectional side view of a portion of the gas-only cartridge <NUM> as shown in <FIG>, including a portion of the base flange <NUM> and a portion of the end cover <NUM> according to at least one embodiment. As shown in <FIG>, the base flange <NUM> and/or the end cover <NUM> may at least partially define a fuel circuit <NUM> for providing a gaseous fuel to the fuel passage <NUM> of the gas-only cartridge <NUM>. As shown in <FIG> and <FIG>, the base flange <NUM> defines a plurality of circumferentially spaced apertures <NUM> that provide for fluid communication between the fuel circuit <NUM> and the fuel passage <NUM>. In particular embodiments, the base flange <NUM> may define one or more air circuits for providing a purge or cooling medium to the air passage <NUM> of the gas-only cartridge <NUM>.

As shown in <FIG> and <FIG>, the fuel distribution tip <NUM> incudes and/or defines a plurality of fuel ports <NUM> circumferentially spaced about the fuel distribution tip <NUM>. The fuel ports <NUM> provide for fluid communication between the fuel passage <NUM> and one or more of the channels <NUM>. In one embodiment, an outer surface <NUM> of the fuel distribution tip <NUM> and the inner surface <NUM> of the tip body <NUM> form multiple seals therebetween so as to at least partially fluidly isolate each channel <NUM> from circumferentially adjacent channels <NUM>.

In various embodiments, as shown in <FIG>, each fuel port <NUM> is aligned with and/or in fluid communication with one corresponding channel <NUM>. In particular embodiments, one or more of the fuel ports <NUM> may be oriented so as to direct a flow of a gaseous fuel radially outwardly from the outer surface <NUM> of the fuel distribution tip <NUM> into each respective channel <NUM> in a direction that is substantially perpendicular to a flow of compressed air flowing through the channel <NUM>. In particular embodiments, one or more of the fuel ports <NUM> may be angled with respect to the axial centerline of the fuel nozzle <NUM>. For example, one or more of the fuel ports <NUM> may be angled into or towards the upstream surface <NUM> of the tip body <NUM>. In addition or in the alternative, in particular embodiments, one or more of the fuel ports <NUM> may be angled towards the downstream surface <NUM> of the tip body <NUM>. In one embodiment, as shown in <FIG>, at least one fuel port <NUM> is axially offset from circumferentially adjacent fuel ports <NUM> with respect to an axial centerline of the gas-only cartridge <NUM>.

As shown in <FIG> and <FIG>, the fuel distribution tip <NUM> includes and/or defines at least one aperture <NUM> that provides for fluid communication from the air passage <NUM> through the fuel distribution tip <NUM>. The aperture <NUM> generally extends through a downstream surface <NUM> of the fuel distribution tip <NUM>.

<FIG> is a flow diagram of the fuel nozzle <NUM> as shown in <FIG>, according to at least one embodiment of the present disclosure. <FIG> provides an enlarged cross sectional side view of a portion of the fuel nozzle <NUM> as shown in <FIG>, including a portion of the center body <NUM>, the tip body <NUM> and a portion of the gas-only cartridge <NUM>. During premix operation of the fuel nozzle <NUM>, as shown in schematically in <FIG>, a first portion of compressed air <NUM> such as the compressed air <NUM> from the compressor <NUM> (<FIG>) enters the inlet <NUM> of the primary premix air passage <NUM>. The turning vanes <NUM> impart angular swirl to the first portion of compressed air <NUM>. Gaseous fuel <NUM> flows into the base portion <NUM> and is routed to the turning vane <NUM> where it is injected into the first portion of compressed air <NUM> via the plurality of fuel ports <NUM>, thereby producing a primary fuel-air mixture downstream from the turning vanes <NUM>. The primary fuel-air mixture <NUM> flows from the outer sleeve <NUM> into the combustion chamber or zone <NUM> (<FIG>) via the outlet <NUM>.

A second portion of compressed air <NUM> may be routed into the secondary premix air passage <NUM>. In particular embodiments, the second portion of compressed air <NUM> is routed from the primary premix air passage <NUM> through one or more passages or holes defined in and/or by the center body <NUM> and into the secondary premix air passage <NUM>. As shown in <FIG>, the second portion of compressed air <NUM> is then routed into each of the channels <NUM> of the tip body <NUM>. Gaseous fuel <NUM> flows from the fuel circuit <NUM> (<FIG>) and into the fuel passage <NUM> of the gas-only cartridge <NUM> via the apertures <NUM>.

As shown in <FIG>, the gaseous fuel <NUM> flows into each of the respective channels <NUM> via fuel ports <NUM>. The second portion of compressed air <NUM> in each respective channel <NUM> mixes with the gaseous fuel <NUM> so as to provide a secondary fuel-air mixture <NUM> to the combustion chamber <NUM>.

In particular embodiments, a purge or cooling medium <NUM> such as compressed air flows into and through the air passage <NUM>. The purge medium <NUM> exits the air passage <NUM> via the aperture <NUM> or a plurality of apertures <NUM>, thereby cooling a downstream surface of the fuel distribution tip <NUM> of the gas-only cartridge <NUM>. In particular embodiments, a portion of the second portion of compressed air <NUM> may be routed through the cooling passages <NUM> (<FIG>), thereby providing cooling to the downstream surface <NUM> of the tip body <NUM>.

Claim 1:
A fuel nozzle (<NUM>), comprising a center body (<NUM>) and a gas-only cartridge (<NUM>) that extends axially within the center body (<NUM>);
the center body (<NUM>) comprising: a tip body (<NUM>) disposed at a downstream end thereof, the tip body defining an opening (<NUM>) that extends axially through the tip body and including a plurality of channels (<NUM>) circumferentially spaced and positioned along an inner surface (<NUM>) of the tip body (<NUM>) within the opening (<NUM>), wherein each channel (<NUM>) defines a flow passage through an upstream surface (<NUM>) and a downstream surface (<NUM>) of the tip body (<NUM>),
the gas-only cartridge (<NUM>) comprising:
a flange (<NUM>) defining a plurality of apertures (<NUM>) for receiving a gaseous fuel;
an outer tube (<NUM>) coupled to the flange (<NUM>) and extending axially outwardly from the flange (<NUM>);
an inner tube (<NUM>) extending axially within the outer tube (<NUM>), wherein the inner tube (<NUM>) and the outer tube (<NUM>) define a fuel passage (<NUM>) therebetween, wherein the fuel passage (<NUM>) is in fluid communication with the plurality of apertures (<NUM>) of the flange (<NUM>);
wherein the inner tube (<NUM>) at least partially defines an air passage (<NUM>) within the gas-only cartridge (<NUM>);
wherein the outer tube (<NUM>) and the center body (<NUM>) having an annular or tube shape define a secondary premix air passage (<NUM>) therebetween;
wherein the flange (<NUM>) at least partially defines at least one air circuit (<NUM>), wherein the air circuit (<NUM>) is in fluid communication with the air passage (<NUM>);
a fuel distribution tip (<NUM>) disposed at a downstream end of the gas-only cartridge (<NUM>), the fuel distribution tip (<NUM>) defining a plurality of fuel ports (<NUM>) circumferentially spaced along and annularly arranged about an outer surface of the fuel distribution tip (<NUM>), wherein the fuel ports (<NUM>) are in fluid communication with the fuel passage (<NUM>) and one or more of the channels (<NUM>); and
wherein the fuel distribution tip (<NUM>) defines an aperture (<NUM>) disposed along a downstream surface (<NUM>) of the fuel distribution tip (<NUM>), wherein the aperture (<NUM>) is in fluid communication with the air passage (<NUM>) in a way that only compressed air (<NUM>) from the air passage (<NUM>) exits via the aperture (<NUM>).