DYNAMICS

FIELD OF THE INVENTION

[0001] The present disclosure is generally directed to a fuel nozzle assembly for reducing multiple tone combustion dynamics. In particular embodiments, the fuel nozzle assembly may be incorporated into a combustion system of a gas turbine or other turbomachine.

BACKGROUND

[0002] Gas turbines are widely used in industrial and power generation operations. A gas turbine generally includes, in serial flow order, a compressor, a combustion section and a turbine. The combustion section may include multiple combustors annularly arranged around an outer casing. In operation, a working fluid such as ambient air is progressively compressed as it flows through the compressor. A portion of the compressed working fluid is routed from the compressor to each of the combustors where it is mixed with a fuel and burned in a combustion chamber or zone to produce combustion gases. The combustion gases are routed through the turbine along a hot gas path where thermal and/or kinetic energy- is extracted from the combustion gases via turbine rotors blades coupled to a rotor shaft, thus causing the rotor shaft to rotate and produce work and/or thrust.

[0003] During particular operating conditions, low frequency combustion tones with sufficient amplitudes, which are m-phase and coherent, may produce undesirable sympathetic vibrations in the turbine and/or other downstream components, thereby imposing undesirable and unnecessary restrictions on the function and operability of the combustor. Low frequency tones are commonly equivalence ratio driven tones. In other words, low frequency tones may result from fluctuations in air feed flow or fuel feed flow to a combustion zone within the combustor.

[0004] Typically, low frequency combustion tones are managed by employing known combustor tuning techniques. However, it has been found that conventional combustor tuning techniques may only be sufficient to address or control only a single dominant tone in the combustion system. BRIEF DESCRIPTION OF TOE TECHNOLOGY

[0005] Aspects and advantages are set forth below in the following description, or may be obvious from the description, or may be learned through practice.

[0006] One embodiment of the present disclosure is a fuel nozzle assembly. The fuel nozzle assembly includes a center body comprising an outer sleeve and an internal fuel passage defined within the outer sleeve. The internal fuel passage defines a fuel flow path within the center body and includes an inlet defined at an upstream end of the center body. The inlet is formed to receive fuel from a fuel supply. The fuel nozzle assembly also includes a plurality of vanes that extend radially outwardly from the outer sleeve and at least one of the vanes includes at least one fuel port that is in fluid communication with the internal fuel passage. At least one baffle extends radially into the internal fuel passage downstream from the inlet and upstream from the at least one fuel port such that the at least one baffle reduces fuel flow area within the internal fuel passage upstream from the at least one fuel port.

[0007] Another embodiment of the present disclosure is a combustion system. The combustion system includes an end cover that is coupled to an outer casing and that is in fluid communication with a fuel supply. A plurality of fuel nozzle assemblies is spaced radially and circumferentially across an inner surface of the end cover and includes a first fuel nozzle assembly that is in fluid communication with a first fuel circuit and a second fuel nozzle assembly in fluid communication with a second fuel circuit. The first fuel nozzle assembly includes a center body comprising an outer sleeve and an internal fuel passage defined within the outer sleeve. The internal fuel passage defines a fuel flow path within the center body. The internal fuel passage includes an inlet that is defined at an upstream end of the center body and that is in fluid communication with the first fuel circuit. A plurality of vanes extends radially outwardly from the outer sleeve and at least one of the vanes includes at least one fuel port that is in fluid communication with the internal fuel passage. The first fuel nozzle assembly further includes at least one baffle that extends radially into the internal fuel passage downstream from the inlet and upstream from the at least one fuel port. The at least one baffle reduces fuel flow area within the fuel flow path.

[0008] Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A full and enabling disclosure of the of various embodiments, 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:

[0010] FIG. 1 is a functional block diagram of an exemplar}' gas turbine that may incorporate various embodiments of the present disclosure;

[0011] FIG. 2 is a simplified cross-section side view of an exemplary combustor as may incorporate vari ous embodiments of the present disclosure;

[0012] FIG. 3 is an upstream view of an end cover including a plurality of fuel nozzle assemblies according to one embodiment of the present disclosure;

[0013] FIG. 4 is a simplified cross sectional view of an exemplar}' fuel nozzle assembly according to one embodiment of the present disclosure;

[0014] FIG. 5 is a cross sectional upstream view of a center body portion of the fuel nozzle assembly as shown in FIG. 4, according to one or more embodiments of the present disclosure;

[0015] FIG. 6 is a cross sectional upstream view of a center body portion of the fuel nozzle assembly as shown in FIG. 4, according to one or more embodiments of the present disclosure;

[0016] FIG. 7 is a cross sectional partial view of an exemplars' shape of the baffle as shown in FIG. 4, according to one embodiment of the present disclosure;

[0017] FIG. 8 is a cross sectional partial view of an exemplary shape of the baffle as shown in FIG. 4, according to one embodiment of the present disclosure;

[0018] FIG. 9 is a cross sectional partial view of an exemplary' shape of the baffle as shown in FIG. 4, according to one embodiment of the present disclosure;

[0019] FIG. 10 is a simplified cross sectional view of an exemplary fuel nozzle assembly- according to one embodiment of the present disclosure; [0020] FIG. 11 is a cross sectional upstream view of a center body portion of the fuel nozzle assembly as shown in FIG . 4, according to one or more embodiments of the present disclosure:

[0021] FIG. 12 is a cross sectional upstream view of a center body portion of the fuel nozzle assembly as shown in FIG. 4, according to one or more embodiments of the present disclosure;

[0022] FIG. 13 is a cross sectional partial view of an exemplary shape of the baffle as shown in FIG. 4, according to one embodiment of the present disclosure:

[0023] FIG. 14 is a cross sectional partial view of an exemplary shape of the baffle as shown in FIG. 4, according to one embodiment of the present disclosure;

[0024] FIG. 15 is a cross sectional partial view of an exemplary shape of the baffle as shown in FIG. 4, according to one embodiment of the present disclosure; and

[0025] FIG. 16 is a cross sectional side view of an exemplar} _' combustion system according to at least one embodiment of the present disclosure.

DETAILED DESCRIPTION

[0026] Reference will now be made in detail to present embodiments of the disclosure, 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 disclosure.

[0027] As used herein, the terms "first", '"second", and "third" may be used

interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms "upstream" and

"downstream." refer to the relative direction with respect to fluid flow in a fluid pathway. For example, "upstream" refers to the direction from which the fluid flows, and "downstream" refers to the direction to which the fluid flows. 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. [0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms '"a", "an" and ^" 'the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or

"comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0029] Low frequency tones observed in gas turbine combustion systems, particularly combustion systems having premix type fuel nozzle assemblies, are typically equivalence ratio driven tones. In oilier words, fluctuations from air flow path or fuel flow paths may drive these tones. Depending at least in part on the tones generated, flow area of fuel ports d efined along vanes of the fuel nozzle assembly may be sized to ad dress or mitigate possible negative effects of specific single tones. However, this tuning strategy has its limitations. For example, sizing the flow area of the fuel ports may only address one dominating tone present in the sy stem.

[0030] Various embodiments provided herein allow for 'mixed impedance' tuning of the combustion system by providing a baffle or flow restriction plate within an internal fuel passage defined within a centerbody portion of a premix type fuel nozzle assembly. The baffle(s) are defmed within the internal flow passage upstream from the fuel ports and downstream from a fuel inlet and/or a flow restrictor disposed upstream from the inlet to the internal fuel passage. The baffle can be placed so as to engineer the acoustic impedance and to reduce the equivalence ratio oscillations within the combustion system.

[0031] 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 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 disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents. Although exemplary embodiments of the present disclosure will be described generally in the context of a fuel nozzle assembly and a combustion system 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 disclosure 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.

[0032] Referring now to the drawings, FIG. 1 illustrates a schematic diagram of an exemplary gas turbine 10. The gas turbine 10 generally includes an inlet section 12, a compressor 14 disposed downstream of the inlet section 12, a combustion system 16 including at least one combustor 18 disposed downstream of the compressor 14, a turbine 20 disposed downstream of the combustor 18 and an exhaust section 22 disposed downstream of the turbine 20. Additionally, the gas turbine 10 may include one or more shafts 24 that couple the compressor 14 to the turbine 20.

[0033] During operation, air 26 flows through the inlet section 12 and into the compressor 14 where the air 26 is progressively compressed, thus providing compressed air 28 to the combustor 18. Fuel 30 from a fuel supply 32 is injected into the combustor 16, mixed with a portion of the compressed air 28 and burned to produce combustion gases 34. The combustion gases 34 flow from the combustor 18 into the turbine 20, wherein energy (kinetic and/or thermal) is transferred from the combustion gases 34 to rotor blades (not shown), thus causing shaft 24 to rotate. The mechanical rotational energy may then be used for various purposes such as to power the compressor 14 and/or to generate electricity. The combustion gases 34 exiting the turbine 20 may then be exhausted from the gas turbine 10 via the exhaust section 22.

[0034] The combustion system 16 may be any type of combustion system 16 known in the art, and the present disclsoure is not limited to any particular combustion system design unless specifically recited in the claims. For example, the combustion system 16 may be a can-annular or an annular combustion system. FIG. 2 provides a side view of a portion of an exemplary combustion system 16 including a can-annular combustor 18 as may be incorporated in the gas turbine 10 shown in FIG. 1 and as may incorporate one or more embodiments of the present disclosure.

[0035] As shown in FIG. 2, the combustor 18 may be at least partially surrounded an outer casing 36 such as a compressor discharge casing. The outer casing 36 may be formed from a single casing or from one or more casings coupled together. The outer casing 36 may at least partially define a high pressure plenum 38 that at least partially surrounds various components of the combustor 18. The high pressure plenum 38 may be in fluid

communication with the compressor 16 (FIG. 1) so as to receive the compressed air 28 therefrom. An end cover 40 may be coupled to the outer casing 36. In particular embodiments, the outer casing 36 and the end cover 40 may at least partially define a head end volume or portion 42 of the combustor 18. In particular embodiments, the head end portion 42 is in fluid communication with the high pressure plenum 38 and/or the compressor 14,

[0036] The combustor 18 may also include one or more liners such as a combustion liner 44 and/or a transition duct 46 that at least partially define a combustion chamber or reaction zone 48 within the outer casing 36. The combustion liner 44 and/or the transition duct 46 may also at least partially define a hot gas path 50 for directing the combustion gases 34 into the turbine 20. In particular configurations, one or more flow or impingement sleeves 52 may at least partially surround the combustion liner 44 and/or the transition duct 46. The flow sleeve(s) 52 may be radially spaced from the combustion liner 44 and/or the transition duct 46 so as to define an annular flow path 54 for directing a portion of the compressed air 28 towards the head end portion 42 of the combustor 18.

[0037] In various embodiments, as shown in FIG. 2, the combustor 18 includes one or more fuel nozzle assemblies 100 coupled to the end cover 40 and extending towards the combustion chamber 48, In particular embodiments, the fuel nozzle assemblies 100 are in fluid communication with the fuel supply 32. FIG. 3 provides an upstream view of the end cover 40 including a plurality of the fuel nozzle assemblies 100 according to one embodiment of the present disclosure. As shown in FIG. 3, the plurality of fuel nozzle assemblies 100 are radially and circumferentially arranged and/or spaced across the end cover 40 relative to a longitudinal or axial axis of the end cover 40.

[0038] Various embodiments of the combustor 18 may include different numbers and arrangements of the fuel nozzle assemblies 100 and is not limited to six fuel nozzle assemblies 100 as shown in FIG. 3 unless otherwise specified in the claims. One of ordinary skill in the art will readily appreciate that besides the circular shape shown in FIG. 3, other shapes and arrangements for the fuel nozzle assemblies 100 from the teachings herein may be employed, and, thus, the particular shape and arrangement of the fuel nozzles 100 are not limitations of the present disclosure, unless specifically recited in the claims.

[0039] The fuel nozzle assemblies 100 may be divided into various groups or circuits to facilitate multiple fueling regimes over a range of operations of the gas turbine and/or the combustor 18. For example, in the exemplary arrangements shown in FIG. 3, a center fuel nozzle assembly 100 may define a primary fuel nozzle group and may receive fuel from a first fuel supply line 56 in fluid communication with the fuel supply 32 (FIG. 2), while the surrounding outer fuel nozzle assemblies 100 may be grouped as secondary and/or tertiary fuel nozzle groups to receive the same or a different fuel from respective secondary and tertiary fuel supply lines 58, 60.

[0040] FIG. 3 illustrates one particular arrangement of the fuel nozzle assemblies 100 in which a secondary fuel nozzle group of two non-adjacent fuel nozzle assemblies 100 is supplied by the second fuel supply line 58 and a tertiary- fuel nozzle group of three fuel nozzle assemblies 100 is supplied by the third fuel supply line 60. However, other groupings of fuel nozzle assemblies 100 may instead be used including groupings that include the center fuel nozzle assemble 100 and one or more of the surrounding fuel nozzle assemblies 100.

[0041] During base load operations, all of the fuel lines 56, 58, 60 may be used to supply- fuel to the fuel nozzle assemblies 100 in the combustor 18 (with respective fuel lines 56, 58, 60 supplying respective primary, secondary, and tertiary groupings of the fuel nozzle assemblies 100. Fuel flow may be reduced or completely eliminated from one or more groups of the fuel nozzle assemblies 100 during reduced or turndown operations via primary, secondary, and tertiary gas control valves (not shown) connected to the corresponding fuel lines 56, 58, 60. Furthermore, according to one aspect of the present disclosure, relative fuel flow to one or more of the fuel lines 56, 58, 60 may be varied at a given operating condition, while maintaining constant total fuel flow in each combustor 18, to alter the combustion dynamics amplitudes and/or frequencies and/or to alter the emissions generated by the combustion system.

[0042] FIG. 4 provides a simplified cross sectional view of an exemplary fuel nozzle assembly 100 as may incorporate various embodiments of the present disclosure. In various embodiments, as shown in FIG. 4, the fuel nozzle assembly 100 includes a center body 102 comprising an outer sleeve 104 and an internal fuel passage 106 defined within the outer sleeve 102. In particular embodiments, the internal fuel passage 106 may be defined between the outer sleeve 104 and an inner sleeve 108 which is coaxially aligned with and extending at least partially through the outer sleeve 104. The internal fuel passage 106 defines a fuel flow path 110 within the center body 02. The internal fuel passage 1 6 includes an inlet 112 defined at an upstream end 114 of the center body 102. The inlet 112 is formed to receive fuel 30 from the fuel supply 32.

[0043] A plurality of vanes 116 extend radially outwardly from the center body 1 2. in particular embodiments, the fuel nozzle assembly 100 includes an outer shroud 1 18 that circumferentially surrounds at least a portion of the center body 102. The outer shroud 118 is radially spaced from the center body 102 so as to define a premix flow passage 120 is therebetween. The plurality of vanes 116 extend from the center body 102 within the premix flow passage 120 and may be connected to the outer shroud 118.

[0044] One or more v anes 1 16 of the plurality of v anes 116 may be contoured or angled with respect to a longitudinal centerline or axis 122 of the center body 102 so as to impart angular or circumferential swirl to the compressed air 28 and/or to fuel 30 that is injected into the premix flow passage 120 from the internal fuel passage 106 via at least one fuel port 124 defined by or within one or more of the v anes 116 and which is in fluid communication with the internal fuel passage 106 during operation of the combustor 18. One or more of the vanes 116 may include a plurality of fuel ports 124 in fluid communication with the internal fuel passage 1 6, The fuel port(s) 124 may have any shape and may be sized the same or have different effective flow areas.

[0045] In various embodiments, as shown in FIG. 4, the fuel nozzle assembly 100 includes at least one baffle or flow restrictor 126 that extends radially into the internal fuel passage 106 downstream from the inlet 112 and upstream from the at least one fuel port 124. The baffle 126 reduces effective fuel flow area within the fuel flow path 110 and/or within the internal flow passage 106 upstream from the at least one fuel port 124 and downstream from the inlet 112, thereby affecting fuel flow through the internal fuel passage 106 and effecting combustion tones generated within the combustion system 16 during operation. The fuel nozzle assembly 100 may include any number of baffles 126 that extend radially into the internal flow passage 106 to affect the flow of fuel 30 flowing between the inlet 1 12 and the fuel port(s) 124. [0046] In particular embodiments, as shown in FIG. 4, at least one baffle 126 is disposed proximate or closer to the fuel port(s) 124 and distal or further away from the inlet 112 with respect to the longitudinal axis 122 of the center body 102. In particular embodiments, at least one baffle 126 is disposed proximate or closer to the inlet 1 12 and distal and distal or further away from the fuel port(s) 124 with respect to the longitudinal axis 122 of the center body 102. In one embodiment, the fuel nozzle assembly includes a pluralit - of baffles 126 longitudinally spaced within the internal fuel passage 106.

[0047] FIG. 5 provides a cross sectional upstream view of the center body 102 including an exemplary baffle 126 according to one or more embodiments. FIG. 6 provides a cross sectional view of the center body 102 including an exemplary baffle 126 according to at least one embodiment. In particular embodiments, as shown in FIGS. 4, 5 and 6, at least one baffle 126 extends radially inwardly from the outer sleeve 104 into the internal fuel passage 106. The baffle 126 may extend circuinferentially about an inner surface 128 of the outer sleeve 104 with respect to the longitudinal axis 122 of the center body 102. In particular embodiments, as shown in FIG. 5, the baffle 126 may extend continuously about an inner surface 128 of the center body 102 and/or the outer sleeve 104. In particular embodiments, as shown in FIG. 6, the baffle 126 may extend circumferential!} _' about the inner surface 128 in arcuate segments 130,

[0048] The baffle 126 may have any cross sectional shape. For example, as shown in FIG. 7, at least one baffle 126 may have a radially inner portion 132 that is at least partially triangular. As shown in FIG. 8, at least one baffle 126 may have a radially inner portion 134 that is at least partially arcuate shaped. In particular embodiments, as shown in FIG. 9, at least one baffle 126 may have a cross sectional shape that converges towards the longitudinal axis 122, Tire shape of each baffle 126 may be same or may be different depending on a desired effect on the flow of fuel 30 through the internal fuel passage 106.

[0049] FIG. 10 provides a simplified cross sectional view of an exemplary fuel nozzle assembly 100 as may incorporate various embodiments of the present disclosure. In various embodiments, as shown in FIG. 10 at least one baffle 126 extends radially outwardly from the inner sleeve 108 into the internal fuel passage 106 downstream, from the inlet 112 and upstream from the at least one fuel port 124. In particular embodiments, as shown in FIG. 10, at least one baffle 126 is disposed proximate or closer to the fuel port(s) 124 and distal or further away from the inlet 112 with respect to the longitudinal axis 122 of the center body 102. In particular embodiments, at least one baffle 126 is disposed proximate or closer to the inlet 112 and distal and distal or further away from the fuel port(s) 124 with respect to the longitudinal axis 122 of the center body 102, In one embodiment, the fuel nozzle assembly 100 includes a plurality of baffles 126 longitudinally spaced within the internal fuel passage 106, In particular embodiments, the fuel nozzle assembly 100 may include at least one baffle 126 that extends radially inwardly into the inter fuel passage 106 from the outer sleeve 104 and at least one baffle 126 that extends radially outwardly from the inner sleeve 108 into the internal fuel passage 106.

[0050] FIG. 1 1 provides a cross sectional upstream view of the center body 102 including an exemplar}' baffle 126 according to one or more embodiments. FIG. 12 provides a cross sectional vie of the center body 102 including an exemplary baffle 126 according to at least one embodiment. In particular embodiments, as shown in FIGS, 10, 11 and 12, at least one baffle 126 extends radially outwardly from the inner sleeve 108 into the internal fuel passage 106. The baffle 126 may extend circumferentially about an outer surface 136 of the inner sleeve 108 with respect to the longitudinal axis 122 of the center body 102. In particular embodiments, as shown in FIG , 11, at least one baffle 126 may extend continuously about an inner surface 128 of the inner sleeve 108, In particular embodiments, as shown in FIG. 12, at least one baffle 126 may extend circumferentially about the inner surface 128 in arcuate segments 138.

[0051] The baffle(s) 126 may have any cross sectional shape. For example, as shown in FIG, 13, at least one baffle 126 may have a radially inner portion 140 that is at least partially triangular. As shown in FIG. 14, at least one baffle 126 may have a radially inner portion 142 that is at least partially arcuate shaped. In particular embodiments, as shown in FIG. 15, at least one baffle 126 may have a cross sectional shape that diverges radially away or outwardly from the longitudinal axis 122. The shape of the baffle(s) 126 may be same or may be different depending on a desired effect on the flow of fuel 30 through the internal fuel passage 106.

[0052] In various embodiments, multiple fuel nozzle assemblies 100 may be incorporated into the combustion system 16 to control or negate multiple combustion tones of the combustor 18. FIG. 16 provides a cross sectioned side view of a portion of the combustor 18 according to one embodiment. In one embodiment, the combustor 18 includes a plurality of fuel nozzle assemblies 100 spaced radially and circumferentially across an inner surface 144 of the end cover 40. The plurality of fuel nozzle assemblies 100 includes a first fuel nozzle assembly 1 0(a) in fluid communication with a first fuel circuit 146 and a second fuel nozzle assembly 100(b) in fluid communication with a second fuel circuit 148. In particular embodiments, the first fuel circuit 146 and/or the second fuel circuit 148 may be defined within the end cover 40. The fi rst fuel circuit 146 and/or the second fuel circuit 148 may be fiddly coupled to any of the fuel lines 56, 58 or 60 shown in FIG. 3.

[0053] As shown in FIG. 13, the internal fuel passage 106(a) of the first fuel nozzle assembly 100(a) is in fluid communication with the first fuel circuit 146 via inlet 112(a). The first fuel nozzle assembly 100(a) includes at least one baffle 126(a) that extends radially into the internal fuel passage 106(a) downstream from the inlet 112(a) and upstream from the at least one fuel port 124(a). The second fuel nozzle assembly 100(b) includes at least one baffle 126(b) that extends radially into the internal fuel passage 106(b) downstream from the inlet 1 12(b) and upstream from the at least one fuel port 124(b).

[0054] In particular embodiments, the baffle 126(a) of the first fuel nozzle assembly 100(a) may be longitudinally offset a specific longitudinal distance 150 from the baffle 126(b) of the second fuel nozzle assembly 100(b), particularly where the first fuel circuit 146 and the second fuel circuit 148 are operated at different fuel flow rates such as during base load and/or during turn down operation of the combustion system 16. In other words, the baffle 126(a) of the first fuel nozzle assembly 100(a) may be positioned at a first longitudinal distance Dl from the inlet 112(a) of the internal fuel passage 106(a) of the first fuel nozzle assembly 100(a), and the at least one baffle of 126(b) the second fuel nozzle assembly 100(b) is positioned within the internal fuel passage 106(b) of the second fuel nozzle assembly 100(b) at a second longitudinal distance D2 from the inlet 112(b) of the internal fuel passage 106(b) of the second fuel nozzle assembly 100(b). The first longitudinal distance Dl may be greater than or less than the second longitudinal distance D2.

[0055] In particular embodiments, the combustion system 16 includes at least one flow restrictor or orifice 152 disposed within or upstream from the first fuel circuit 146 and/or at least one flow restrictor or orifice 154 disposed within or upstream from the second fuel circuit 148. The at least one flow restrictor 152 may be positioned upstream from the inlet 112(a) to the intemal fuel passage 106(a) of the first fuel nozzle assembly 100(a). In addition or in the alternative, the at least one flow restrictor 154 may be positioned upstream from the inlet 112(b) to the internal fuel passage 106(b) of the second fuel nozzle assembly 100(b).

[0056] The size and/or shape of the baffle(s) 126(a), 126(b) and/or longitudinal position withm the center body 102(a). 102(b) may be determined based at least in part on the diameter or flow area of the fuel port(s) 124(a), 124(b), the diameter or flow area of the flow restrictors 152, 154, and/or one or more combustion tones or frequencies generated by the combustion system during particular operating modes such as during turn down or full speed operation, or based at least in part on particular operating parameters such as fuel type.

[0057] 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 language of the claims.