Method for igniting liquid fuel in turbomachinery - Patent Application 20070122997

Abstract

To provide methods of igniting a liquid fuel in a turbomachine.SOLUTION: A method of igniting a liquid fuel (58) in a turbomachine combustor (22) is provided. The method includes a step of initiating a flow of a gaseous fuel (28) from a gaseous fuel supply source (228) to a gaseous fuel nozzle (322). The method further includes a step of initiating a flow of the liquid fuel (58) from a liquid fuel supply source (158) to a primary liquid fuel cartridge (358). After initiating both the flow of the gaseous fuel (28) and the flow of the liquid fuel (58), the method includes a step of igniting the flow of the gaseous fuel (28) and the flow of the liquid fuel (58) with an igniter (370). The method further includes a step of terminating the flow of the gaseous fuel (28) from the gaseous fuel supply source (228) to the gaseous fuel nozzle (322).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to a method for igniting liquid fuel in a turbomachine, and more particularly to a method for igniting liquid fuel in a combustor of a turbomachine. [Background technology]

[0002] Turbomachines are utilized in various industries and applications for the purpose of energy transfer. For example, a gas turbine engine typically includes a compressor section, a combustion section, a turbine section, and an exhaust section. The compressor section gradually increases the pressure of a working fluid entering the gas turbine engine and supplies the compressed working fluid to the combustion section. The compressed working fluid and fuel (e.g., natural gas) are mixed in the combustion section and combusted in a combustion chamber to generate high-pressure and high-temperature combustion gases. The combustion gases flow from the combustion section to the turbine section, where they expand to produce work. For example, the expansion of the combustion gases in the turbine section can rotate a rotor shaft connected to, for example, a generator, to generate electricity. The combustion gases then exit the gas turbine through the exhaust section.

[0003] In the combustion section, the fuel nozzles can operate on gas fuel only, liquid fuel only, or gas and liquid fuel simultaneously. Often, power plants may need to operate for a given period of time using only liquid fuel. In these instances, plant operators have found it convenient to transition from gas-fuel operation to liquid-fuel operation. However, there are instances when the primary gas fuel supply is unavailable. In these cases, the challenge has been to ignite the liquid fuel during startup without relying on the primary gas fuel supply to achieve the transfer.

[0004] One challenge with igniting liquid fuels during startup is ensuring the proximity of the igniter to the region of the ignitable liquid spray. If the igniter is not close enough to the ignitable liquid spray, ignition cannot occur. Some conventional ignition systems rely on spark igniters positioned within the flame zone and then retracted due to the pressure of the ignited combustion gases. Such spark igniters can suffer accelerated wear due to their proximity to the hot combustion gases, especially if the retraction mechanism does not function properly.

[0005] Challenges with igniting liquid fuels arise in combustion systems that use cross-fire tubes to propagate the flame between arrays of combustors. In these systems, if the combustible liquid does not span the width of the combustor (and therefore falls within the confines of the cross-fire tubes), proper flame propagation through the combustors will not occur. This problem can be exacerbated when the liquid fuel is delivered from a centrally located liquid fuel cartridge.

[0006] Another challenge with igniting liquid fuels occurs in combustion systems with non-intersecting liquid fuel jets emerging from liquid fuel cartridges. In such systems, when operating solely on liquid fuel, it can be difficult or impossible to ignite each of the non-intersecting fuel jets.

[0007] Existing methods for igniting liquid fuel in a combustion system often rely on the presence of a pre-established flame. For example, liquid fuel is typically ignited by first flowing and igniting gaseous fuel through one or more fuel nozzles, followed by flowing liquid fuel through one or more liquid fuel cartridges. The pre-existing flame from the gaseous fuel exiting the fuel nozzles propagates to and ignites the liquid fuel exiting the liquid fuel cartridges. However, problems exist with this method for igniting liquid fuel in a combustion system.

[0008] For example, because combusting gaseous fuels is often prioritized over liquid fuels in combustion systems, turbomachines typically transition to burning liquid fuels only when the gaseous fuel supply begins to run low or becomes unavailable. Therefore, it is important that the gaseous fuel balance is efficiently managed to ensure that the turbomachine can perform multiple starts and transition to liquid-only operation. Thus, methods that rely on a pre-established gaseous flame require a relatively large amount of gaseous fuel, which adversely affects the number of possible starts.

[0009] Therefore, there is a need in the art for an improved method for igniting liquid fuels that does not require the presence of a pre-established gas combustion flame, and in particular, there is a need in the art for an improved method for igniting liquid fuels in combustion systems that advantageously minimizes the amount of gaseous fuel used during start-up. Summary of the Invention

[0010] Aspects and advantages of methods according to the present disclosure will be set forth in part in the description that follows, or will be obvious from the description, or may be learned by practice of the present techniques.

[0011] According to one embodiment, a method of igniting liquid fuel in a turbomachine combustor is provided. The method includes initiating a flow of gaseous fuel from a gaseous fuel supply to a gaseous fuel nozzle. The method further includes initiating a flow of liquid fuel from the liquid fuel supply to a primary liquid fuel cartridge. After initiating both the gaseous fuel flow and the liquid fuel flow, the method includes igniting the gaseous fuel flow and the liquid fuel flow with an igniter. The method further includes terminating the flow of gaseous fuel from the gaseous fuel supply to the gaseous fuel nozzle.

[0012] According to another embodiment, a method for starting a gas turbine with liquid fuel is provided. The gas turbine includes a rotor shaft attached to a compressor and a turbine. The gas turbine further includes a plurality of combustors disposed between the turbine and the compressor. The method further includes accelerating rotation of the rotor shaft toward a combustion speed to force air through the gas turbine. The method includes initiating a flow of gaseous fuel from a gaseous fuel supply to a gaseous fuel nozzle. The method further includes initiating a flow of liquid fuel from a liquid fuel supply to a primary liquid fuel cartridge. After initiating both the gaseous fuel flow and the liquid fuel flow, the method includes igniting the gaseous fuel flow and the liquid fuel flow with an igniter. The method further includes terminating the flow of gaseous fuel from the gaseous fuel supply to the gaseous fuel nozzle.

[0013] These and other features, aspects, and advantages of the present method will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present technology and, together with the description, serve to explain the principles of the technology.

[0014] A full and enabling disclosure of the present system and method, including the best mode of making and using the same, directed to one of ordinary skill in the art, is set forth in this specification, which makes reference to the accompanying figures. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a turbomachine according to an embodiment of the present disclosure; [Figure 2] 1 is a schematic cross-sectional view of a combustor and liquid fuel ignition system according to an embodiment of the present disclosure; [Figure 3] FIG. 2 is a side view of a liquid fuel cartridge according to an embodiment of the present disclosure. [Figure 4] FIG. 2 is a top view of a cartridge tip of a liquid fuel cartridge according to an embodiment of the present disclosure. [Figure 5]FIG. 2 is a top plan view (aft-forward view) of a first exemplary combustor head end according to an embodiment of the present disclosure. [Figure 6] FIG. 2 is a plan view (aft-forward looking) of a second exemplary combustor head end according to an embodiment of the present disclosure. [Figure 7] 3 is a flowchart of a method for igniting liquid fuel in a turbomachine combustor according to an embodiment of the present disclosure. [Figure 8] 1 is a flowchart of a method for starting a gas turbine with liquid fuel according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] Reference will now be made in detail to embodiments of the present method, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the present technology, not as a limitation thereof. Indeed, it will be apparent to those skilled in the art that modifications and variations can be made in the present technology without departing from the scope or spirit of the claimed technology. For example, features illustrated or described as part of one embodiment can be used in another embodiment to yield yet a further embodiment. Accordingly, the present disclosure is intended to cover such modifications and variations as come within the scope of the appended claims and their equivalents.

[0017] The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description are used to refer to like or similar parts of the invention. As used herein, the terms "first," "second," and "third" can be used interchangeably to distinguish one component from another and are not intended to denote the location or importance of individual components.

[0018] As used herein, the terms "upstream" (or "forward") and "downstream" (or "aft") refer to relative directions with respect to fluid flow in a fluid pathway. For example, "upstream" refers to the direction from which fluid flows, and "downstream" refers to the direction from which fluid flows. The term "radially" refers to relative directions that are substantially perpendicular to the axial centerline of a particular component, the term "axially" refers to relative directions that are substantially parallel to and / or coaxially aligned with the axial centerline of a particular component, and the term "circumferentially" refers to relative directions that extend around the axial centerline of a particular component.

[0019] Approximate terms such as "generally" or "about" include values ​​within plus or minus 10 percent of the stated value. When used in the context of angles or directions, such terms include a range of plus or minus 10 degrees of the stated angle or direction. For example, "generally vertical" includes any direction, e.g., clockwise or counterclockwise, within 10 degrees of vertical.

[0020] Referring now to the drawings, Figure 1 shows a schematic diagram of one embodiment of a turbomachine, which in the illustrated embodiment is a gas turbine 10. Although an industrial or land-based gas turbine is shown and described herein, the present disclosure is not limited to industrial and / or land-based gas turbines unless otherwise stated in the claims. For example, the methods described herein may be used with any type of turbomachine, including, but not limited to, a steam turbine, an aircraft gas turbine, or a marine gas turbine.

[0021] As shown, the gas turbine 10 is a heavy-duty gas turbine used to generate electricity. The gas turbine 10 includes an inlet section 12 that may generally include a series of filters, cooling coils, water separators, and / or other devices for cleaning and otherwise conditioning a working fluid (e.g., air) 24 entering the gas turbine 10. The working fluid 24 flows to a compressor section where the compressor 14 progressively imparts kinetic energy to the working fluid 24 to generate a compressed working fluid 26.

[0022] The compressed working fluid 26 is mixed with the gaseous fuel 28 or liquid fuel mixture 58 to form a combustible mixture in one or more combustors 22 of the combustion section or system 16. The gaseous fuel 28 may originate from a main gaseous fuel supply system 128 (e.g., a gaseous fuel pipeline) via a main gaseous fuel supply line 170, or from an auxiliary gaseous fuel source 228 (e.g., a storage tank) via an auxiliary gaseous fuel supply line 270. In various embodiments, a gaseous fuel supply valve 135 may be positioned in fluid communication with the main gaseous fuel supply line 170 and the auxiliary gaseous fuel supply line 270 so that the gaseous fuel 28 is delivered from a single source (either the main gaseous fuel supply system 128 or the auxiliary gaseous fuel supply system 228). The liquid fuel mixture 58 originates from a liquid fuel supply system 158 (e.g., a mixing tank) in which the liquid fuel 38 and water 40 are mixed and delivered to the combustor 22 via a liquid fuel supply line 160. A liquid fuel supply valve 165 controls the delivery of liquid fuel 58 .

[0023] The combustible mixture, which may include gas and / or liquid fuel, is combusted to generate high-temperature, high-pressure, and high-velocity combustion gases 30. The combustion gases 30 flow through the turbine 18 of the turbine section to generate work. For example, the turbine 18 may be connected to the shaft 17 so that rotation of the turbine 18 drives the compressor 14 to generate compressed working fluid 26. Alternatively, or in addition, the shaft 17 may connect the turbine 18 to a generator 20 for generating electricity.

[0024] Exhaust gases 32 from the turbine 18 flow through an exhaust section (not shown) that connects the turbine 18 to an exhaust stack downstream of the turbine. The exhaust section may include, for example, a heat recovery steam generator (not shown) for cleaning and extracting additional heat from the exhaust gases 32 before they are released to the environment.

[0025] The combustors 22 may be any type of combustor known in the art, and the method is not limited to any particular combustor design unless specifically recited in the claims. For example, in some embodiments, the combustors 22 may comprise a can-type or can-annular-type combustion section, with each combustor 22 having its own individual combustion chamber that generates a portion of the combustion gases 30. In other embodiments, the combustors 22 may be annular-type combustion sections in which combustion occurs in a common annulus supplied by a circumferential array of burners (fuel nozzles).

[0026] 2 is a schematic diagram of a combustor 22 that may be included in a can-annular combustion system 16 for a heavy-duty gas turbine 10. In the can-annular combustion system 16, multiple combustors 22 (e.g., 8, 10, 12, 14, 16, or more) are positioned in an annular array about a shaft 17 that connects the compressor 14 to a turbine 18. Each combustor 22 of the multiple combustors has its own local combustion chamber such that combustion gases 30 can flow from each can-annular combustor 22 toward the turbine section 18.

[0027] As shown in FIG. 2 , the combustor 22 includes a liner 312 that contains and channels the combustion gases 30 to the turbine. The liner 312 may define a combustion chamber in which combustion occurs. The liner 312 may have a cylindrical liner portion and a tapered transition portion separate from the cylindrical liner portion, as in many conventional combustion systems. Alternatively, the liner 312 may have a one-piece body (or “unibody”) configuration in which the cylindrical portion and the tapered portion are integrated with one another. Thus, the description of the liner 312 herein is intended to encompass both conventional combustion systems having separate liners and transition pieces and combustion systems having unibody liners. Furthermore, the present disclosure is equally applicable to combustion systems in which the transition piece and the turbine's first-stage nozzle are integrated into a single unit, sometimes referred to as a “transition nozzle” or “integrated outlet piece.”

[0028] Liner 312 is surrounded by outer sleeve 314, which is spaced radially outward from liner 312 to define an annulus 332 between liner 312 and outer sleeve 314. Outer sleeve 314 may include a flow sleeve portion at its forward end and an impingement sleeve portion at its aft end, as in many conventional combustion systems. Alternatively, outer sleeve 314 may have a one-piece body (or "unisleeve") configuration in which the flow sleeve portion and the impingement sleeve portion are axially integrated with one another. As previously mentioned, the description of outer sleeve 314 herein is intended to encompass both conventional combustion systems having separate flow and impingement sleeves and combustion systems having a unisleeve outer sleeve.

[0029] A head end portion 320 of the combustor 22 includes one or more fuel nozzles 322. The fuel nozzles 322 have a fuel inlet 324 at an upstream (or inlet) end. The fuel inlet 324 may be formed through an end cover 326 at the forward end of the combustor 22. The downstream (or outlet) ends of the fuel nozzles 322 may extend into and / or through a combustor cap 328 (also shown in FIG. 4 ) or may be attached to the cap ( FIG. 6 3. The rear plate 368 functions as a rear plate 368 (shown in FIG. 3).

[0030] In many embodiments, the head end portion 320 of the combustor 22 may be at least partially surrounded by a forward casing, which is physically coupled and fluidly connected to the compressor discharge case. In various embodiments, the compressor discharge case may be fluidly connected to an outlet of the compressor 14 and define a compressed air plenum that surrounds at least a portion of the combustor 22. The compressed air 26 may flow from the compressor discharge case through openings defined in the outer sleeve 314 to an annulus 332 at the aft end of the combustor 22. Because the annulus 332 is fluidly coupled to the head end portion 320, the airflow 26 travels upstream from the aft end of the combustor 22 to the head end portion 320, where the airflow 26 turns and enters the fuel nozzles 322. For example, the air 26 may travel through the annulus 332 in a direction opposite to that of the combustion gases 30 within the liner 312.

[0031] The fuel 28 and compressed air 26 are introduced by fuel nozzles 322 into a combustion chamber 350 at the forward end of the liner 312, where the fuel 28 and air 26 are ignited via an igniter 370 and combusted to form combustion gases 30. The igniter 370 is positioned proximate the head end 320 of the combustor 22. Alternatively, the igniter may be a torch-type igniter 380 positioned within the head end 320 of the combustor 22 (e.g., through an end cover 326 upstream of one of the fuel nozzles 322). The combustion gases 30 from one combustor 22 travel through a cross-fire tube (not shown) between the liners 312 of adjacent combustors 22, propagating a flame around the array of combustors 22.

[0032] In one embodiment, the fuel 28 and air 26 are mixed within the fuel nozzle 322 (e.g., in a premix fuel nozzle). In other embodiments, the fuel 28 and air 26 may be introduced separately into the combustion chamber 350 and mixed within the combustion chamber 350 (e.g., as may occur in a diffusion nozzle). References herein to a "fuel / air mixture" should be interpreted as describing both premixed and diffusion-type fuel / air mixtures, either of which may be generated by the fuel nozzle 322.

[0033] For liquid fuel operation, the liquid fuel mixture 58 is delivered to the liquid fuel cartridge 358 via the liquid fuel supply line 160. In the exemplary embodiment, the liquid fuel cartridge 358 is located along the axial centerline 310 of the combustor 22 and is coaxially positioned within one of the fuel nozzles 322. In many embodiments, the liquid fuel cartridge 358 may extend coaxially with both the combustor 22 and the fuel nozzle 322.

[0034] Combustion gases 30 generated by burning the gaseous fuel 28 and / or liquid fuel 58 with the compressed air 26 travel downstream toward an aft frame 318 of the combustor 22, which represents the aft end of the combustor 22. In many embodiments, the aft frame 318 may be connected to the turbine 18 such that the combustion gases 30 may exit the combustor section 16 at the aft frame 318 and enter the turbine 18.

[0035] A control system, or controller 400, may be used to control the fuel 28, 58 provided to the combustor 22. The control system 400 may communicate via signal 435 with gaseous fuel supply valves 135 located along the main gaseous fuel supply line 170 and the auxiliary gaseous fuel supply line 270, such that the gaseous fuel 28 is directed from one or both of these supply lines 170 or 270 through the valves 135 to the gaseous fuel supply line 70. The control system 400 also communicates via signal 465 with the liquid fuel supply valve 165 located along the liquid fuel supply line 160. In some embodiments, the control system 400 sends a start signal 470 to the igniter 370 during startup of the combustor 22. In other embodiments, the control system 400 sends a start signal 480 to the torch-type igniter 380 during startup of the combustion system.

[0036] Flame detector 412 or 414 (labeled "S" in FIG. 2 to indicate the sensor) may be used to detect flame within combustion chamber 350. Flame detector 412 is disposed in or through end cover 326 and positioned to detect flame within combustion chamber 350, looking through the upstream end of fuel nozzle 322. Flame detector 414 may be disposed along the inner surface of liner 312 and positioned to detect flame within combustion chamber 350, looking upstream (i.e., looking aft to forward) from the downstream end of combustor 22 to head end 320. Flame detector 412 or 414 communicates with controller 400, such that detection of a flame is sent to controller 400 as signals 422, 424. Flame detector 412, 414 may be any type of flame detector known in the art, including, but not limited to, an optical detector, a spectrometer, a camera, an ultraviolet flame detector, an infrared flame detector, a heat detector, a pressure sensor, or a combination thereof.

[0037] FIG. 3 illustrates a liquid fuel cartridge 358 that can be used with the combustor 22 of FIG. 2 . The liquid fuel cartridge 358 includes a cylindrical body 360, a liquid fuel cartridge tip 362, and a mounting flange 366 that defines an inlet 364 that receives the liquid fuel mixture 58 from the liquid fuel supply line 160. As shown, in many embodiments, the cartridge tip can include a base 361 that couples directly to the cylindrical body 360, the base 361 being the axially innermost portion of the cartridge tip 362 with respect to the axial direction A. As shown in FIG. 3 , the cartridge tip 362 can diverge radially inward from the base 361 to a downstream face 363, and the cartridge tip 362 has a generally conical shape. The conical shape of the cartridge tip 362 can be advantageous over a cylindrical shape, for example, to provide an aerodynamic profile that minimizes the possibility of fuel vortices or hot spots along the cartridge tip 362. In various embodiments, as best shown in Figure 2, the cartridge tip 362 may be disposed entirely within the combustion chamber 350 and terminate at a downstream face 363 positioned downstream of the combustor cap 328. As shown in Figure 3, the cartridge tip 362 may define a row of liquid fuel injection holes 364 circumferentially spaced apart from one another on the cartridge tip 362.

[0038] FIG. 4 illustrates the cartridge tip 362 from a slightly downstream, upstream perspective. As shown in FIGS. 3 and 4 , the liquid fuel injection holes 364 can deliver the liquid fuel mixture 58 in a direction oblique and / or perpendicular to the delivery of the fuel / air mixture from the fuel nozzle 322. As shown in FIG. 4 , the liquid fuel injection holes 364 can be clustered in circumferentially offset groups so that the streams of liquid fuel mixture 58 exiting the cartridge tip 362 do not overlap one another. Thus, a flame from one stream of liquid fuel mixture generally does not propagate to another stream of liquid fuel without the presence of gaseous fuel. In some embodiments, the downstream surface 363 can define one or more liquid fuel injection holes 365 therethrough that deliver the liquid fuel mixture 58 in a direction parallel to the delivery of the fuel / air mixture from the fuel nozzle 322, i.e., parallel to the axial direction A.

[0039] 5 is a plan view of a first embodiment of a combustor head end 320a in which the liquid fuel cartridge 358 of FIGS. 3 and 4 is installed. As shown, the liquid fuel cartridge 358 may be a primary liquid fuel cartridge 357 installed within a central fuel nozzle 322a, such as a swirl fuel nozzle, swozzle, or other suitable fuel nozzle. The central fuel nozzle 322a is surrounded by a plurality of outer fuel nozzles 322b, which may also be swirl fuel nozzles, swozzles, or other suitable fuel nozzles. As shown, one or more secondary liquid fuel cartridges 359, which may have a configuration similar to the liquid fuel cartridge 358, may be disposed within one or more of the outer fuel nozzles 322b.

[0040] Each fuel nozzle 322a, 322b may include a swirl vane 323 that imparts swirl to the air flowing therethrough. In some embodiments, the swirl vanes 323 of the outer fuel nozzles 322b are disposed about a central hub 321. In other embodiments, the swirl vanes 323 may be disposed about a secondary liquid fuel cartridge 359, as shown. In the exemplary embodiment, each of the outer fuel nozzles 322b may include a central hub 321, such that the only liquid fuel cartridge 358 is a primary liquid fuel cartridge 357 disposed in the central fuel nozzle 322a. The swirl vanes 323 in the central fuel nozzle 322a may be disposed about the primary liquid fuel cartridge 357. While six outer fuel nozzles 322b are shown, it should be understood that other numbers of fuel nozzles 322b (e.g., four, five, or eight fuel nozzles 322b) may be used. The fuel nozzles 322a, 322b are installed in corresponding openings (not separately labeled) in the combustor cap 328.

[0041] FIG. 6 is a plan view of a second embodiment of a combustor head end 320b in which the liquid fuel cartridge 358 of FIGS. 3 and 4 is installed. As shown, the liquid fuel cartridge 358 may be a primary liquid fuel cartridge 357 installed within a central fuel nozzle 322c, such as a bundle-tube fuel nozzle. The central fuel nozzle 322c is surrounded by multiple fuel nozzles 322d, which may also be bundle-tube fuel nozzles. As shown, one or more secondary liquid fuel cartridges 359, which may have a configuration similar to the liquid fuel cartridge 358, may be disposed within one or more of the fuel nozzles 322d. Each bundle-tube fuel nozzle 322c, 322d includes multiple individual premixer tubes 522 where fuel and air are mixed. The premixer tubes 522 extend through an aft plate 368, which may be unique to each bundle-tube fuel nozzle 322c, 322d or may extend across all of the bundle-tube fuel nozzles 322c, 322d.

[0042] The bundle-tube fuel nozzles 322 c, 322 d may include an upstream fuel plenum unique to each fuel nozzle 322 c, 322 d, and each premixer tube 522 may include one or more fuel injection ports in fluid communication with the fuel plenum. Air flowing through the inlet end of each premixer tube 522 mixes with fuel flowing through the fuel injection ports, and the fuel-air mixture is channeled through the outlet end of each tube 522.

[0043] Alternatively, each premixer tube 522 may include an inlet end where a fuel lance is located. A plurality of air inlet holes are located downstream of the fuel lance so that air flowing through the air inlet holes mixes with fuel from the fuel lance. The fuel and air mixture is conveyed through the outlet end of each tube 522.

[0044] Although the bundle-tube fuel nozzle 322d is shown as having a sector shape including two radially extending sides and two oppositely arranged arcuate sides, it should be understood that the bundle-tube fuel nozzle 322d may have any shape or size relative to the central bundle-tube fuel nozzle 322c.

[0045] 7 is a flowchart of a sequential set of steps 710-760 defining a method 700 of igniting liquid fuel in a gas turbine combustor according to one embodiment of the present disclosure. The flowchart includes schematic diagrams to illustrate the respective flows from the fuel nozzle 322 and liquid fuel cartridge 358 of the combustor 22 of FIG. 2.

[0046] 7 by the dotted box, method 700 may include optional step 710. Optional step 710 may include detecting the absence of an active flame within combustion chamber 350 using one or more flame detectors, such as flame detectors 412, 414. As described herein, flame detectors 412, 414 are operable to sense the presence of a flame within combustion chamber 350 and communicate the sensed data to controller 400 via signals 422, 424.

[0047] Step 720 includes initiating the flow of gaseous fuel 28 from the gaseous fuel supply to the gaseous fuel nozzle 322. Step 730 includes initiating the flow of liquid fuel 58 from the liquid fuel supply to the primary liquid fuel cartridge 357. As shown in FIG. 2 , the gaseous fuel supply may be the main gaseous fuel supply 128, the auxiliary gaseous fuel supply 228, or both. Similarly, the liquid fuel supply may be the liquid fuel supply system 158. Steps 720 and 730 may be performed by sending a signal 435 to the gaseous fuel supply valve 135 and a signal 465 to the liquid fuel supply valve 165 to open both valves 135, 165 prior to ignition in the combustor and provide gaseous and liquid fuel to the combustion zone 350.

[0048] In the exemplary embodiment, the method 700 advantageously does not require ignition of the gaseous fuel 28 before the flow of the liquid fuel 58 is initiated, allowing for more efficient use of the gaseous fuel 28. In this manner, the gaseous fuel 28 can be efficiently utilized to maximize the number of starts when operating the gas turbine 10 on liquid fuel 58.

[0049] In some embodiments, steps 720 and 730 may be performed simultaneously. In such embodiments, a signal 435 to open the gas fuel supply valve 135 and a signal 465 to open the liquid fuel supply valve 165 may be sent simultaneously to simultaneously provide gas fuel 28 and liquid fuel 58 within the combustor 22. As shown in FIG. 2 , opening the gas fuel supply valve 135 may allow gas fuel to flow from the primary gas fuel source 128, the auxiliary fuel source 228, or both, through the fuel supply line 70 to the gas fuel nozzle 322. Similarly, opening the liquid fuel supply valve 165 may allow liquid fuel to flow from the liquid fuel supply system 158 through the liquid fuel supply line 160 to the liquid fuel cartridge 358. As a result, as shown in diagram 735, a gas fuel / air mixture is delivered from the gas fuel nozzle 322 to the combustion zone 350, and liquid fuel 58 is delivered from the primary liquid fuel cartridge 357 to the combustion zone 350, prior to ignition within the combustor 22.

[0050] In step 740, after both steps 720 and 730 have been performed, controller 400 initiates an igniter, such as igniter 370 or torch igniter 380, by sending signals 470 and / or 480 to igniter 370 and / or torch igniter 380. Performing steps 720 and 730 before 740 advantageously allows for simultaneous ignition of gaseous fuel 28 and liquid fuel 58, thereby conserving gaseous fuel.

[0051] In many embodiments, the gas fuel 28 and liquid fuel 58 may be ignited via an igniter 370 positioned downstream of the gas fuel nozzle 322 and the liquid fuel cartridge 358. The igniter 370 may generate a spark that ignites the gas fuel / air mixture within the combustion chamber 350.

[0052] In the exemplary embodiment, the gas fuel 28 and liquid fuel 58 may be ignited via a torch igniter 380 positioned within the head end 320 of the combustor 22 (e.g., through an end cover 326 upstream of one of the fuel nozzles 322). The flame generated by the gas fuel / air mixture immediately propagates to the liquid fuel 58 exiting the primary liquid fuel cartridge 358 because liquid fuel 58 is present within the combustor 22 at the moment of gas fuel ignition.

[0053] The method 700 may also include the optional step 750 of detecting the presence of a flame emanating from both the gas fuel nozzle 322 and the liquid fuel cartridge 358 in the combustion zone 350 using one or more flame detectors 412, 414. The controller 400 may receive signals 422, 424 from one or both of the flame detectors 412, 414 indicating that combustion is occurring in the combustion chamber and that a flame is emanating from the gas fuel nozzle 322 and the liquid fuel cartridge 358. This step may be performed to confirm that the liquid fuel 58 exiting the liquid fuel cartridge 358 has ignited.

[0054] In step 760, the controller 400 can terminate the gas fuel supply to the gas fuel nozzle 322 by sending a second signal 435 only to the gas fuel supply valve 135. The gas fuel supply valve 135 closes the passage between the gas fuel supply line 170 and / or 270 and the gas fuel supply line 70. The passages from the gas fuel supply line 170 to the gas fuel supply line 70 and from the gas fuel supply line 270 to the gas fuel supply line 70 remain closed, thereby not allowing gas fuel 28 to travel through the gas fuel supply line 70 to the gas fuel nozzle 322. As a result, as shown in diagram 765, only the liquid fuel mixture 58 is delivered from the liquid fuel cartridge 358, and the gas fuel nozzle 322 is not supplied with fuel (i.e., it can deliver only air). The controller 400 can initiate step 760 based on a timeline or based on receipt of signals 422 or 424, if step 750 is included.

[0055] 8 is a flowchart of a sequential set of steps 810-870 defining a method 800 for starting a gas turbine with liquid fuel according to another aspect of the present disclosure. As described in detail above, the gas turbine 10 may include a rotor shaft 17 coupled to a compressor 14 and a turbine 18, and a plurality of combustors 22 may be disposed between the turbine 18 and the compressor 14. As shown in FIG. 8, the flowchart includes a schematic diagram to illustrate the respective flows from the fuel nozzles 322 and liquid fuel cartridges 358 of the combustors 22 of FIG. 2.

[0056] The method 800 may include accelerating the rotation of the rotor shaft 17 toward the combustion speed and forcing 810 air through the gas turbine 10. Forcing the air through the gas turbine 10 includes flowing the air through the combustor 22, for example, through one or more gas fuel nozzles 322, so that the air is in the combustion chamber before combustion occurs. Once the rotor shaft reaches the combustion speed, fuel may begin to be delivered to the gas fuel nozzles 322 and / or the liquid fuel cartridges 358.

[0057] 8 by the dotted box, method 800 may include optional step 820. Optional step 820 may include detecting the absence of an active flame within combustion chamber 350 using one or more flame detectors, such as flame detectors 412, 414. As described herein, flame detectors 412, 414 are operable to sense the presence of a flame within combustion chamber 350 and communicate the sensed data to controller 400 via signals 422, 424.

[0058] Step 830 includes initiating the flow of gas fuel from the gas fuel source to the gas fuel nozzle 322. Step 840 includes initiating the flow of liquid fuel from the liquid fuel source to the primary liquid fuel cartridge 357. As shown in FIG. 2 , the gas fuel source may be the main gas fuel source 128, the auxiliary gas fuel source 228, or both. Similarly, the liquid fuel source may be the liquid fuel supply system 158. Steps 830 and 840 may be performed by sending a signal 435 to the gas fuel supply valve 135 and a signal 465 to the liquid fuel supply valve 165 to open both valves 135, 165 prior to ignition in the combustor 22 and provide gas fuel 28 and liquid fuel 58 to the combustion zone 350.

[0059] In the exemplary embodiment, the method 800 advantageously does not require ignition of the gaseous fuel 28 before the flow of the liquid fuel 58 is initiated, allowing for more efficient use of the gaseous fuel 28. In this manner, the gaseous fuel 28 can be efficiently utilized to maximize the number of starts when operating the gas turbine 10 on liquid fuel 58.

[0060] In some embodiments, steps 830 and 840 may be performed simultaneously. In such embodiments, a signal 435 to open the gas fuel supply valve 135 and a signal 465 to open the liquid fuel supply valve 165 may be sent simultaneously to simultaneously provide gas fuel 28 and liquid fuel 58 within the combustor 22. As shown in FIG. 2 , opening the gas fuel supply valve 135 may allow gas fuel to flow from the primary gas fuel source 128, the auxiliary fuel source 228, or both, through the fuel supply line 70 to the gas fuel nozzle 322. Similarly, opening the liquid fuel supply valve 165 may allow liquid fuel to flow from the liquid fuel supply system 158 through the liquid fuel supply line 160 to the liquid fuel cartridge 358. As a result, as shown in diagram 845, a gas fuel / air mixture is delivered from the gas fuel nozzle 322 to the combustion zone 350, and liquid fuel 58 is delivered from the primary liquid fuel cartridge 357 to the combustion zone 350, prior to ignition within the combustor 22.

[0061] In step 850, controller 400 initiates an igniter, such as igniter 370 or torch igniter 380, by sending signals 470 and / or 480 to igniter 370 and / or torch igniter 380. In many embodiments, gaseous fuel 28 and liquid fuel 58 may be ignited via igniter 370 positioned downstream of gaseous fuel nozzle 322 and liquid fuel cartridge 358. Igniter 370 may generate a spark that ignites the gaseous fuel / air mixture in combustion chamber 350.

[0062] In the exemplary embodiment, the gas fuel 28 and liquid fuel 58 may be ignited via a torch igniter 380 positioned within the head end 320 of the combustor 22 (e.g., through the upstream end cover 326 of one of the fuel nozzles 322). The flame generated by the gas fuel / air mixture immediately propagates to the liquid fuel 58 exiting the primary liquid fuel cartridge 357 because liquid fuel 58 is present within the combustor 22 at the moment of gas fuel ignition.

[0063] The method 800 may also include the optional step 860 of detecting the presence of a flame emanating from both the gas fuel nozzle 322 and the liquid fuel cartridge 358 in the combustion zone 350 using one or more flame detectors 412, 414. The controller 400 may receive signals 422, 424 from one or both of the flame detectors 412, 414 indicating that combustion is occurring in the combustion chamber 350 and that the flame is emanating from the gas fuel nozzle 322 and the liquid fuel cartridge 358. This step may be performed to confirm that the liquid fuel 58 exiting the liquid fuel cartridge 358 has ignited.

[0064] In step 870, the controller 400 can terminate the gas fuel supply to the gas fuel nozzle 322 by sending a second signal 435 only to the gas fuel supply valve 135. The gas fuel supply valve 135 closes the passage between the gas fuel supply line 170 and / or 270 and the gas fuel supply line 70. The passages from the gas fuel supply line 170 to the gas fuel supply line 70 and from the gas fuel supply line 270 to the gas fuel supply line 70 remain closed, thereby not allowing gas fuel 28 to travel through the gas fuel supply line 70 to the gas fuel nozzle 322. As a result, as shown in diagram 875, only the liquid fuel mixture is delivered from the liquid fuel cartridge 358, and the gas fuel nozzle 322 is not fueled (i.e., it can deliver only air). The controller 400 can initiate step 870 based on a timeline or based on receipt of signals 422 or 424, if step 860 is included.

[0065] In many embodiments, methods 700 and 800 may be performed with access to only an auxiliary fuel supply source, such as the auxiliary fuel supply system 228 described herein. In such embodiments, the main gaseous fuel supply system 128 may not be available. Therefore, it is very important that the gaseous fuel from the auxiliary fuel supply system 228 is efficiently managed to ensure that the gas turbine can perform multiple starts and operate on liquid fuel.

[0066] Thus, within tens of seconds (e.g., less than a minute), the combustor 22 can be successfully started and operated on liquid fuel. The methods 700, 800 described herein advantageously enable the gas turbine 10 to start without a pre-established flame in the combustor 22, which advantageously minimizes the amount of gaseous fuel required at start-up, thereby efficiently managing the fuel supply available in the auxiliary fuel supply system 228 over a maximum number of start-ups. In particular, the methods 700, 800 described herein may be advantageous over methods requiring a pre-established flame, i.e., "fuel transfer methods," because the methods 700, 800 require significantly less gaseous fuel than the fuel transfer methods. For example, in the fuel transfer method, gaseous fuel is ignited in the combustor before liquid fuel is introduced, which requires a majority of the gaseous fuel from the auxiliary fuel source. Using this method, multiple starts can be achieved from a single gaseous fuel tank 228, thereby providing greater operational flexibility to plant operators.

[0067] Methods and systems described herein facilitate ignition of liquid fuel in a gas turbine combustor. More specifically, the methods and systems facilitate ignition of liquid fuel without accessing a primary gaseous fuel supply. Accordingly, the methods and systems facilitate improving the overall operational flexibility of a combustor, such as a combustor in a gas turbine assembly. This may reduce costs associated with operating a combustor, such as a combustor in a gas turbine assembly, and / or increase the operating time (and power output) of the combustor.

[0068] Exemplary embodiments of methods for igniting liquid fuel have been described in detail above. The methods described herein are not limited to the specific embodiments described herein; rather, components of the methods can be utilized independently and separately from other components described herein. For example, the methods described herein may have other applications that are not limited to practice in the turbine assemblies described herein. Rather, the methods and systems described herein can be implemented and utilized in connection with a variety of other industries.

[0069] This written description uses examples to disclose the invention, including the best mode, and 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 contain structural elements that do not differ from the literal language of the claims, or equivalent structural elements that do not differ substantially from the literal language of the claims. [Explanation of symbols]

[0070] 10. Gas turbine 12 Entrance Section 14 Compressor 16 Combustion section, can-annular combustion system, combustor section 17 rotor shaft 18 Turbine Section 20. Generator 22 Combustor, can-annular combustor, turbomachinery combustor 24 Working Fluid 26 Compressed working fluid, compressed air, air flow 28 Gaseous fuels 30 Combustion Gas 32 Exhaust gas 38 Liquid fuel 40 water 58 Liquid fuel mixture, liquid fuel 70 Gaseous fuel supply line 128 Main gaseous fuel supply system, main gaseous fuel supply source 135 Gaseous fuel supply valve 158 Liquid Fuel Supply System 160 Liquid fuel supply line 165 Liquid fuel supply valve 170 Main gaseous fuel supply line 228 Auxiliary gaseous fuel supply sources, auxiliary gaseous fuel supply systems, gaseous fuel tanks 270 Auxiliary gaseous fuel supply line 310 Axial centerline 312 Liner 314 Outer sleeve 318 Rear Frame 320 Head end part 320a Combustor head end 320b combustor head end 321 Central Hub 322 Gaseous fuel nozzle 322a Center Fuel Nozzle 322b Outer fuel nozzle 322c Center Tube Fuel Nozzle 322d bundle tube fuel nozzle 323 Swirling Vane 324 Fuel inlet 326 End cover 328 Combustor Cap 332 Circular section 350 Combustion chamber, combustion zone 357 Primary Liquid Fuel Cartridge 358 Liquid Fuel Cartridge 359 Secondary Liquid Fuel Cartridge 360 Cylindrical body 361 Base 362 Liquid fuel cartridge tip 363 Downstream side 364 Inlet, liquid fuel injection hole 365 Liquid fuel injection hole 366 Mounting flange 368 Rear Plate 370 Igniter 380 Torch-type igniter, torch igniter 400 Control system, controller 412 Flame detector 414 Flame detector 422 signal 424 signal 435 Second Signal 465 Signal 470 start signal 480 start signal 522 Premixing tube 700 methods 735 Schematic 765 Schematic 800 ways 845 Schematic 875 Schematic A axis direction

Claims

1. A method (700, 800) of igniting a liquid fuel (58) in a turbomachine combustor (22), comprising: Initiating (720, 830) a flow of gaseous fuel (28) from a gaseous fuel supply (228) to a gaseous fuel nozzle (322); Initiating a flow of liquid fuel from a liquid fuel supply to a liquid fuel cartridge, the step of initiating the flow of liquid fuel occurring simultaneously with or subsequent to the step of initiating the flow of gaseous fuel; after starting both the gaseous fuel (28) flow and the liquid fuel (58) flow, simultaneously igniting the gaseous fuel (28) flow and the liquid fuel (58) flow with an igniter (370); terminating (760, 870) the flow of the gaseous fuel (28) from the gaseous fuel supply (228) to the gaseous fuel nozzle (322); A method (700, 800) comprising:

2. 2. The method according to claim 1, wherein the liquid fuel cartridge is positioned along an axial centerline of the turbomachine combustor, the gas fuel nozzle surrounds the liquid fuel cartridge, and the liquid fuel cartridge and the gas fuel nozzle are positioned at a head end of the turbomachine combustor.

3. A method (700, 800) for igniting a liquid fuel (58) in a turbomachine combustor (22), comprising: Initiating (720, 830) a flow of gaseous fuel (28) from a gaseous fuel supply (228) to a gaseous fuel nozzle (322); Initiating (730, 840) the flow of liquid fuel (58) from the liquid fuel source (158) to the liquid fuel cartridge (358); igniting (740, 850) the gaseous fuel (28) and liquid fuel (58) flows with an igniter (370) after initiating both the gaseous fuel (28) and liquid fuel (58) flows; terminating (760, 870) the flow of the gaseous fuel (28) from the gaseous fuel supply (228) to the gaseous fuel nozzle (322); Including, The method (700, 800), wherein the steps (720, 830) of initiating the flow of the gaseous fuel (28) and the steps (730, 840) of initiating the flow of the liquid fuel (58) are performed simultaneously.

4. 2. The method of claim 1, wherein the gaseous fuel supply is one of a main gaseous fuel supply system, an auxiliary gaseous fuel supply system, or both the main gaseous fuel supply system and the auxiliary gaseous fuel supply system.

5. The method of claim 1, further comprising providing a controller in communication with the igniter, the gaseous fuel supply, and the liquid fuel supply.

6. 6. The method of claim 5, further comprising detecting a flame in a combustion chamber of the turbomachine combustor using a flame detector, the flame detector in communication with the controller and transmitting a signal of the flame detection to the controller.

7. 7. The method of claim 6, wherein the steps of initiating the flow of the gaseous fuel and the step of initiating the flow of the liquid fuel occur before the flame detector detects a flame in the combustion chamber.

8. 2. The method of claim 1, wherein the step of initiating the flow of the gaseous fuel from the gaseous fuel supply is accomplished by controlling a gaseous fuel valve located in a gaseous fuel supply line extending from the gaseous fuel supply.

9. 10. The method of claim 8, wherein terminating the flow of the gaseous fuel from the gaseous fuel source is accomplished by controlling the gaseous fuel valve.

10. 2. The method of claim 1, wherein the step of initiating the flow of the liquid fuel from the liquid fuel supply is accomplished by controlling a liquid fuel valve located in a liquid fuel supply line extending between the liquid fuel supply and the liquid fuel cartridge.

11. 1. A method of starting a gas turbine (10) with a liquid fuel (58), the gas turbine (10) comprising a rotor shaft (17) coupled to a compressor (14) and a turbine (18), a plurality of combustors (22) disposed between the turbine (18) and the compressor (14); Accelerating rotation of the rotor shaft (17) toward a combustion speed and forcing air through the gas turbine (10); Within each combustor (22) of the plurality of combustors (22), Initiating (720, 830) a flow of gaseous fuel (28) from a gaseous fuel supply (228) to a gaseous fuel nozzle (322); Initiating a flow of liquid fuel from a liquid fuel supply to a liquid fuel cartridge, the step of initiating the flow of liquid fuel occurring simultaneously with or subsequent to the step of initiating the flow of gaseous fuel; after starting both the gaseous fuel (28) flow and the liquid fuel (58) flow, simultaneously igniting the gaseous fuel (28) flow and the liquid fuel (58) flow with an igniter (370); terminating (760, 870) the flow of the gaseous fuel (28) from the gaseous fuel supply (228) to the gaseous fuel nozzle (322); A method (700, 800) comprising:

12. 12. The method according to claim 11, wherein the liquid fuel cartridge is positioned along an axial centerline of each combustor of the plurality of combustors, the gas fuel nozzle surrounds the liquid fuel cartridge, and the liquid fuel cartridge and the respective gas fuel nozzle are positioned at a head end of each combustor of the plurality of combustors.

13. A method for starting a gas turbine (10) with liquid fuel (58), the gas turbine (10) comprising a rotor shaft (17) coupled to a compressor (14) and a turbine (18), a plurality of combustors (22) disposed between the turbine (18) and the compressor (14); Accelerating rotation of the rotor shaft (17) toward a combustion speed and forcing air through the gas turbine (10); Within each combustor (22) of the plurality of combustors (22), Initiating (720, 830) a flow of gaseous fuel (28) from a gaseous fuel supply (228) to a gaseous fuel nozzle (322); Initiating (730, 840) the flow of liquid fuel (58) from the liquid fuel source (158) to the liquid fuel cartridge (358); igniting (740, 850) the gaseous fuel (28) and liquid fuel (58) flows with an igniter (370) after initiating both the gaseous fuel (28) and liquid fuel (58) flows; terminating (760, 870) the flow of the gaseous fuel (28) from the gaseous fuel supply (228) to the gaseous fuel nozzle (322); Including, The method (700, 800), wherein the steps (720, 830) of initiating the flow of the gaseous fuel (28) and the steps (730, 840) of initiating the flow of the liquid fuel (58) are performed simultaneously.

14. 12. The method (700, 800) of claim 11, wherein the gaseous fuel supply (228) is one of a main gaseous fuel supply (128) system, an auxiliary gaseous fuel supply (228) system, or both the main gaseous fuel supply (128) system and the auxiliary gaseous fuel supply (228) system.

15. The method (700, 800) of claim 11, further comprising providing a controller (400) in communication with the igniter (370), the gaseous fuel supply (228), and the liquid fuel supply (158).

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