FUEL INJECTOR AND NOZZLE FOR A GAS TURBINE, AND GAS TURBINE ENGINE INCLUDE SUCH NOZZLE

Abstract

The fuel injector (19) includes a fuel infeed chamber (21) and a center body (31) extending along a longitudinal axis from the fuel infeed chamber (21) to a distal end (37) of the center body. An outer sleeve (35) surrounds the center body and defines an annular premix chamber (43) between the outer sleeve and the center body. The center body includes a distal tip that projects outside the annular premix chamber beyond the distal end of the outer sleeve.

Description

[Technical field]

[0001] The subject matter disclosed herein relates generally to gas turbine engines. More specifically, the present disclosure relates to a premixed fuel nozzle for a gas turbine engine combustor, as well as a gas turbine engine combustor. [Background technology]

[0002] Gas turbine engines, in both aircraft and industrial applications, include at least one combustor in which fuel in gaseous or liquid form is mixed with a compressed air flow and burned to generate a flow of hot, pressurized combustion gases. The combustion gases are expanded in a turbine that includes one or more turbine stages to generate mechanical power. A portion of the mechanical power generated by the turbine is used to drive the gas turbine engine's compressor and assist in the continuous supply of combustion air to the combustor. The remaining available electrical power is used to drive a load, such as an electrical generator or compressor, or to generate thrust for aircraft propulsion.

[0003] The combustor includes a combustion chamber and a number of fuel nozzles that function to introduce liquid or gaseous fuel into the compressed air flow from the air compressor to obtain a mixture of combustion air and fuel. At start-up, the mixture is ignited to burn the fuel. By continuing to supply compressed air and fuel to the combustor, the combustion process is maintained to generate a continuous flow of compressed hot combustion gases for powering the turbine.

[0004] Control of the flame in the combustor is one of the important aspects of fuel nozzle design. One of the objectives of nozzle design is the reduction of harmful emissions such as nitrogen oxides (NOx), carbon monoxide, and unburned hydrocarbons. Further concerns are the reduction of flame instabilities, the reduction of acoustic pressure dynamics or vibrations (i.e., combustion noise), and the reduction of lean blow-out risk, as well as the reduction of hot spots in the combustion chamber due to, for example, asymmetric temperature profiles.

[0005] In this context, an important aspect is the stability of the flame shape and spatial position, whose changes during the operation of the combustor can adversely affect harmful emissions of the gas turbine engine and increase acoustic pressure dynamics and vibrations. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, improved fuel nozzle designs aimed at reducing flame instabilities with respect to shape and location would be welcomed in the art.

[0007] In the embodiments disclosed herein, the fuel injector includes a fuel infeed chamber having an end wall and a center body extending along a longitudinal axis from the end wall to a distal end of the center body. An outer sleeve surrounds the center body and extends along the axis of the center body from the end wall to a distal end of the outer sleeve opposite the fuel infeed chamber. Thus, an annular premix chamber is formed between the outer sleeve and the center body.

[0008] The premix chamber has an annular outlet at the distal end of the outer sleeve. The centerbody includes a distal tip that terminates at the distal end of the centerbody and projects outside the premix chamber, beyond the distal end of the outer sleeve, and inside the combustion chamber.

[0009] According to further embodiments disclosed herein, the central body has an additional fluid conduit extending along the central body and fluidly coupled to at least one outlet port at a distal tip of the central body. In use, depending on the operating conditions of the gas turbine in which the fuel injector is located, fuel, air, or an air / fuel mixture can be delivered through the additional fluid conduit towards the distal tip of the central body.

[0010] The exit port may be located on or off axis of the central body, in embodiments, two or more exit ports may be provided.

[0011] According to a further aspect, disclosed herein is a fuel nozzle for a gas turbine engine, the fuel nozzle including one or more fuel injectors as generally described above.

[0012] The present disclosure also relates to a combustor assembly for a gas turbine engine. In one embodiment, the combustor assembly has a combustion chamber extending from an upstream end to a downstream end. The downstream end is adapted to be fluidly coupled to a turbine of the gas turbine engine, and the upstream end is further adapted to be fluidly coupled to an air compressor of the gas turbine engine. The combustor assembly also has at least one fuel nozzle as generally described above.

[0013] Also disclosed herein is a gas turbine engine including a combustor assembly.

[0014] In this specification and the appended claims, the terms "upstream" and "downstream" refer to the direction of the air, fuel, or air-fuel mixture, unless otherwise specified. [Brief description of the drawings]

[0015] Reference will now be made briefly to the accompanying drawings, in which: [Figure 1] FIG. 1 is a schematic diagram of a gas turbine engine adapted for use in a variety of useful applications, including industrial applications. [Diagram 2] FIG. 2 is a cross-sectional schematic of a combustor having multiple fuel nozzles and an annular combustion chamber for a gas turbine engine. [Diagram 3] FIG. 3 is an axonometric view of a fuel nozzle. [Figure 4] FIG. 4 is a cross-sectional view of the fuel nozzle of FIG. [Diagram 5] FIG. 5 is a front view of a fuel nozzle in a further embodiment. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a front view of a fuel nozzle in a further embodiment. [Figure 8] FIG. 8 is a cross-sectional view similar to FIG. 6 of a further embodiment. [Figure 9] FIG. 9 is an enlarged detailed view of the distal end of the central body in yet another embodiment. [Figure 10] FIG. 10 is a cross-sectional view of a fuel nozzle in yet another embodiment. [Figure 11] FIG. 11 is a cross-sectional view of a fuel nozzle in yet another embodiment. [Figure 12] FIG. 12 is a front view of a fuel nozzle in yet another embodiment. [Figure 13] FIG. 13 is a cross-sectional view taken along line XIII-XIII in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] To improve flame shape and flame position stability in a combustor for a gas turbine engine, a novel fuel injector is provided having a fuel infeed chamber and a center body extending along a longitudinal axis from a proximal end of the center body adjacent the fuel infeed chamber to a distal end of the center body. The distal end is located downstream of the proximal end with respect to a direction of flow of a fuel-air mixture. An outer sleeve extends around the center body. The outer sleeve extends from the fuel infeed chamber toward the combustion chamber and terminates at an annular edge opposite the fuel infeed chamber. The outer sleeve includes a side opening for supplying air inside an annular premixing chamber, also referred to as a premixer, formed between the center body and the outer sleeve. The center body includes a port for supplying fuel into the annular premixing chamber.

[0017] In operation, air and fuel are premixed in the annular premixing chamber or premixer, and the fuel-air mixture leaving the annular premixing chamber is burned to form a flame extending towards the inside of the combustion chamber. To improve the flame stability, both in terms of flame shape and position, i.e. where the flame is located relative to the fuel nozzle (including one or more of the new fuel injectors), the central body is provided with a distal tip that projects outside the annular premixing chamber beyond the distal end of the outer sleeve. The distal tip that projects beyond the premixing chamber or premixer may have a convex outer surface. In an embodiment, the distal tip has a surface of revolution coaxial with the central body. For example, the distal tip may have a dome shape, a spherical cup shape, a hemispherical shape, an ogive shape, etc. In general, the distal tip has an aerodynamic shape. Advantageously, the distal tip that projects beyond the premixing chamber is connected with a curved surface to the part of the central body within the premixing chamber.

[0018] Embodiments of the present invention are suitable for all types of gas turbine engines, regardless of end use. The fuel injectors disclosed herein can be used in aeroderivative gas turbines, as well as industrial heavy duty gas turbines. While the following description refers to gas turbines for mechanical drive, those skilled in the art will appreciate that the fuel injectors disclosed herein can be used in gas turbines for air propulsion as well as gas turbines for power generation.

[0019] In the following description, specific reference is made to combustors including annular combustion chambers, however, it should be understood that fuel injectors and fuel nozzles incorporating features of the present description may also be used with other types of combustors including, for example, can-type or tube-annular combustion chambers.

[0020] 1 shows, by way of example and not limitation, a schematic diagram of a gas turbine engine 1 configured for use in a variety of applications including, for example, industrial or power generation applications for driving a load 3. The load 3 may include a compressor or compressor train, such as, in one example, a refrigerant compressor of the type that may be used in a plant for the production of liquefied natural gas, or in another example, a gas compressor in a gas pipeline. In other embodiments, the load may be an electrical generator when the gas turbine engine is used for power generation purposes.

[0021] Gas turbine engine 1 includes an air compressor 5, a combustor 7, and a turbine section 9. By way of example only, in Figure 1 turbine section 9 comprises a high pressure turbine 9A and a low pressure turbine 9B. In an embodiment, the high pressure turbine 9A is mechanically coupled to the air compressor 5 to rotationally drive the air compressor 5. The low pressure turbine 9B is drivingly coupled to a load 3 to provide power to drive the load 3.

[0022] 1 is a two-shaft turbine. However, the fuel injector of the present disclosure may also be advantageously used in other types of gas turbines, such as single-shaft or three-shaft gas turbines.

[0023] According to some embodiments, the combustor 7 comprises an annular combustion chamber 11, as shown diagrammatically in Figure 2. The combustion chamber 11 comprises an outer liner 13 and an inner liner 15, which are coaxial with each other and with the axis of rotation AA of the gas turbine engine 3. The combustion chamber 11 extends in an upstream-downstream direction from the air compressor 5 to the turbine section 9. A number of fuel nozzles 17 are arranged in the upstream region of the combustor 7. One of the fuel nozzles 17 is shown in a perspective view in Figure 3 and in a cross-section through a radial plane including the axis of rotation AA in Figure 4.

[0024] Each fuel nozzle 17 generally includes a number of fuel injectors 19, as best shown in Figures 3 and 4 and disclosed in more detail below. Specifically, in the embodiment shown, each fuel nozzle includes four fuel injectors. Two fuel injectors are shown in cross-section in Figure 4. The number of fuel injectors 19 per fuel nozzle 17 is merely exemplary. Additionally, the same combustor may include different fuel nozzles having, for example, different shapes and sizes, and possibly a variable number of fuel injectors.

[0025] Each fuel injector 19 includes a fuel infeed chamber 21 that includes an end wall 23 facing the combustion chamber 11, i.e., oriented toward the combustion chamber 11 and the turbine section 9. The fuel infeed chambers 21 of the fuel injectors 19 belonging to a fuel nozzle 17 may be combined to form a fuel infeed plenum 25. In other embodiments, each fuel infeed chamber 21 may form an individual fuel infeed plenum 25 that is fluidly coupled to a single fuel injector 19.

[0026] The fuel inlet plenum 25 is in fluid communication with a fuel supply duct contained within a fuel injector structure 27 (FIG. 3) from which liquid or gaseous fuel is delivered to the fuel inlet plenum 25 and from there to the fuel injectors 19 .

[0027] Each fuel injector 19 further includes a central body 31 extending along the longitudinal axis BB from a proximal or upstream end at the end wall 23 toward a distal or downstream end 33 of the central body 31 facing the interior of the combustion chamber 11 and the turbine section 9.

[0028] Each fuel injector 19 further includes an outer sleeve 35. The outer sleeve 35 may be coaxial with the respective central body 31. In other embodiments, the central body 31 and the outer sleeve 35 may not be coaxial with one another.

[0029] Each outer sleeve 35 extends from a proximal end at the end wall 23 of the fuel infeed chamber 21 to a distal end 37. The outer sleeves 35 belonging to the same fuel nozzle 17 are coupled to a common front wall 36.

[0030] In the embodiment shown in FIG. 4, the center body 31 and outer sleeve 35 of the fuel nozzle 17 are all parallel to one another.

[0031] Each outer sleeve 35 includes a plurality of air inlet ports 41 that extend through the outer sleeve 35 and are in fluid communication with an annular premix chamber 43 or premixer formed between the centerbody 31 and the outer sleeve 35. The annular premix chamber 43 has a bottom at the end wall 23 of the fuel infeed chamber 21 and an annular outlet 45 surrounded by the distal end 37 of the outer sleeve 35.

[0032] When the outer sleeve 35 and the central body 31 are coaxial, as shown in FIG. 4, the annular premix chamber 43 and its outlet 45 have a constant radial dimension as shown in the illustrated embodiment. However, as mentioned above, this is not binding. In some embodiments shown, the central body 31 and the outer sleeve 35 may be non-coaxial. In extreme cases, the central body 31 and the outer sleeve 35 may contact each other. In that case, the annular premix chamber 43 and the annular outlet 45 may have a non-constant radial dimension and may even have an interruption along the cross section, because when the central body 31 and the outer sleeve 35 contact each other, the radial dimension of the annular premix chamber and / or the annular outlet 45 becomes zero at the contact area. In this specification and the appended claims, the term "annular" also encompasses configurations in which the annular premix chamber 43 and / or the annular outlet 45 have a radial dimension that varies around the axis of the central body and may become zero at one or more positions around the axis BB.

[0033] Compressed air delivered by the air compressor 5 (see arrow A in FIG. 2) enters each annular premixing chamber 43 through air inlet ports 41 and is premixed with fuel delivered through fuel injection ports provided in the central body 31 described below to generate an air-fuel mixture.

[0034] The distal end 33 of each central body 31 features a distal tip 47 that projects beyond the annular exit 45 of the annular premix chamber 43 and into the combustion chamber 11. In some embodiments, the distal tip 47 has a convex outer surface, e.g., approximately hemispherical, or dome-shaped, or spherical cup-shaped, or ogive-shaped.

[0035] More generally, the distal tip 47 of each centerbody 31 has a portion that protrudes beyond the annular exit 45 of the premix chamber 43 and is shaped to prevent the air / fuel mixture from forming a recirculation area (negative or low axial velocity).

[0036] In some embodiments, the distal tip 47 of the central body 31 tapers from the annular exit 45 of the annular premix chamber 43 towards the combustion chamber 11 and may terminate in a sharp point or a rounded or flat apex. The tapered surface of the distal tip 47 protruding from the annular exit 45 of the annular premix chamber 43 in the combustion chamber 11 is shaped to avoid gas separation from the walls and gas recirculation to prevent the flame from sticking or attaching to the central body 31.

[0037] In some embodiments, the distal tip 47 may have an outer convex surface that may be defined as a surface of revolution generated by a generatrix rotating about the axis BB of the central body 31. As used herein, a generatrix is ​​a curve that generates a surface when moved along a given path. The path that directs the motion of the generatrix is ​​called a directrix. More specifically, in embodiments disclosed herein where the outer convex surface is a surface of revolution, the directrix is ​​a circumferential line. In other embodiments, the directrix may be an elliptical line.

[0038] In some embodiments, each central body 31 comprises a body portion housed inside the premix chamber 43 and connected to a distal tip 37 of the central body protruding outside the premix chamber 43, the body may have a constant or variable cross section. In some embodiments, as illustrated in the accompanying drawings, each central body 31 comprises a first main body portion: a proximal portion 31A and a second distal portion 31B. The first portion 31A is adjacent to the end wall 23 of the fuel infeed chamber 21 and extends towards the distal end 33 of the central body 31. The second portion 31B is located intermediate the first portion 31A and the distal tip 47. The first portion 31A may have a substantially cylindrical shape with a circular or elliptical cross section. The second portion 31B may have a tapered shape, i.e. a substantially frustoconical shape with a circular or elliptical cross section and a lateral dimension (diameter in case of a circular cross section) that increases from the first portion 31A towards the distal tip 47 of the central body 31. As a result, the annular premixing chamber 43 has a constant annular cross-section along a first portion and a tapered or converging annular cross-section that gradually reduces in cross-sectional area towards the annular outlet 45 .

[0039] For example, as can be seen from the cross-sectional view of Fig. 4, the generatrix defining the distal tip 47 of the central body 31 forms a smooth transition zone from the main parts 31A, 31B of the central body located inside the premix chamber 43 to the distal tip 47 of the central body 31 protruding outside the premix chamber 43. Sharp edges in the transition zone are avoided and an aerodynamic shape of the distal tip 47 of the central body 31 is obtained. Thus, the smoothness of the flow of the air / fuel mixture without recirculation is improved.

[0040] A smooth transition zone, as understood herein, may be a zone that is free of sharp edges or corners. Thus, in the area defining the transition zone, the generatrices forming the outer surface of the central body are curves with continuous derivatives.

[0041] The transition zone may extend to the distal end 33 of the central body, i.e., to the most downstream end of the central body. As noted above, the distal tip of the central body may terminate in a cusp or in a flat or planar surface. At the cusp or end flat or planar surface, the derivative of the curve describing the profile may have a discontinuity.

[0042] Generally, the smooth transition zone also includes at least a portion of the tapered distal tip 47 , and preferably the entire tapered portion of the distal tip 47 .

[0043] In general, the annular premix chamber 43 has a distal portion terminating at its outlet 45 which has a converging shape, i.e. the cross-sectional area decreases in a proximal to distal direction towards the distal tip 47 of the central body 31, i.e. in the direction of flow of the air / fuel mixture. In the embodiment shown in the accompanying drawings, the converging shape of the premix chamber is obtained via a conical surface of the central body 31 adjacent its downstream end 33. The air-fuel mixture accelerates as it travels in a proximal to distal direction along the annular premix chamber 43 until it reaches the annular outlet.

[0044] When the perfectly premixed air / fuel mixture formed in the annular premix chamber 43 flows through the annular outlet 45 where the velocity of the air / fuel mixture is rapidly reduced, the aerodynamic shape of the distal tip 47 ensures the correct flame shape and flame location within the combustion chamber.

[0045] In other embodiments, the tapered distal portion of the premix chamber can be obtained by combining a cylindrical shape of the outer surface of the central body 31 with a conical inner surface of the distal portion of the outer sleeve 35. In such a case, the distal portion of the inner surface of the outer sleeve 35 has an inner diameter that gradually decreases moving in the proximal to distal direction.

[0046] The tapered or converging end portion of the premix chamber 43 may also be obtained by a combination of a conical distal portion of the central body and a conical distal portion of the inner surface of the outer sleeve 35 .

[0047] A fuel duct is provided inside the central body 31 to supply fuel to the annular premixing chamber 43. In some embodiments, the central body 31 comprises an axially extending outer tubular wall 51 and an axially extending inner tubular wall 53. The axially extending outer tubular wall 51 and the axially extending inner tubular wall 53 form an annular gap 52 therebetween. More specifically, the axially extending outer tubular wall 51 and the axially extending inner tubular wall 53 extend from the end wall 23 of the fuel infeed chamber 21 towards the distal tip 47 of the respective central body 31. The outer tubular wall 51 is integral with the distal tip 47, and an outer surface of the outer tubular wall 51 merges with a convex surface of the distal tip 47 of the central body 31. The inner tubular wall 53 terminates at a distance from the inner surface of the distal tip 47 of the central body 31.

[0048] In this manner, a fuel conduit is formed inside the central body 31, the fuel conduit extending in a first direction from the fuel infeed chamber 21 along the axial cavity 56 of the inner tubular wall 53 toward the distal end 33 of the central body 31, and in a second opposite direction from the distal end 33 of the central body 31 toward the fuel infeed chamber 21 along an annular gap 52 formed between the inner tubular wall 53 and the outer tubular wall 51. At least one, and preferably a plurality of fuel injection ports 57 extend through the outer tubular wall 51 adjacent an end of the annular gap 52 opposite the distal end 33 of the central body 31. In this manner, fuel is delivered from the fuel infeed chamber 21 through the axial cavity 56, the annular gap 52, and the fuel injection ports 57 into the annular premix chamber 43.

[0049] In the annular premix chamber 43, fuel is mixed with compressed air supplied by the air compressor 5 of the gas turbine engine 1 and flowing through the air inlet port 41. The intimately premixed fuel-air mixture formed in the annular premix chamber 43 flows through annular outlet 45. When the mixture is ignited, a flame is formed downstream of the distal end 33 of each fuel injector 19 and is sustained by the premixed air and fuel continuously supplied through the annular premix chamber 43.

[0050] It has been found that due to the above-described improved shape and geometry of the distal tip 47 of the central body 31, the flame is stable in terms of both its shape and position even under variable operating conditions of the combustor and gas turbine engine 1. This results in reduced harmful emissions, more regular heat loading, reduced combustion noise and vibration, and generally more efficient control of the combustion conditions.

[0051] Specifically, the improved shape of the centerbody 31, and especially its distal tip 47, which has a smooth transition zone from the main body portion inside the premix chamber 43 to the distal tip 47 outside the premix chamber results in an aerodynamic shape of the centerbody. The improved aerodynamic shape provides a more uniform flow of the air / fuel mixture, higher velocities, and an absence of flow recirculation, thus avoiding the risk of the flame pinning on the distal end 37 of the centerbody or outer sleeve 35. Flame stability is improved and the risk of thermal damage to the fuel nozzle due to the flame pinning on metal components of the fuel nozzle is largely prevented.

[0052] Figures 5 and 6 show another embodiment of a fuel nozzle 17 according to the present disclosure. The same reference numbers are used to indicate parts, elements and components already illustrated in Figure 4. The main difference between the embodiment of Figure 4 and the embodiment of Figures 5 and 6 concerns the interior of the central body 31 and the fuel delivery path. In the embodiment of Figures 5 and 6, each central body 31 comprises a number of fuel injection ports 57 arranged near the proximal end of the central body 31, preferably in the area where the air inlet port 41 is located. The fuel injection ports 57 provide a fluid connection between the interior of the central body 31 and the annular premixing chamber 43. The interior of the central body 31 does not have an inner tubular wall 53, but merely forms an extension of the fuel infeed chamber 21.

[0053] 5 and 6, each central body 31 is coaxial with a respective outer sleeve 35, as previously described, although in other configurations different non-coaxial arrangements can be provided. Figure 7 illustrates a front view similar to Figure 5 of a further embodiment in which each central body 31 is non-coaxial with respect to a corresponding outer sleeve 35. Due to the non-coaxial arrangement, the annular premix chamber 43 has a variable radial dimension about the axis BB of the central body 31.

[0054] 7, each central body 31 contacts the inner surface of the outer sleeve 35 at 32 and thus the annular premix chamber 43 has a minimum radial dimension at 32 equal to zero. However, in other embodiments, the non-coaxial arrangement can be such that the central bodies 31 do not contact the inner surface of the outer sleeve 35.

[0055] In the embodiments disclosed thus far, the fuel injectors 19 are parallel to each other, i.e., the axis BB of the central body 31 and the axis of the outer sleeve 35 are all parallel to each other. In other embodiments, at least two fuel injectors 19 may be non-parallel to each other. FIG. 8 illustrates a cross-sectional view similar to FIG. 7 of a fuel nozzle 17 including fuel injectors 19 arranged in a converging configuration such that their axes BB converge toward a point located within the combustion chamber 11. All four fuel injectors 19 may converge toward a central axis CC of the fuel nozzle 17. Alternatively, the axes BB of two pairs of fuel injectors 19 may be arranged in a converging configuration on two parallel planes.

[0056] The non-coaxial arrangement of FIG. 7 and the non-parallel arrangement of FIG. 8 can be combined with each other.

[0057] In the embodiments described thus far, the distal tip 47 has a tapered shape, i.e., a fully convex shape with a cross-section that decreases moving from proximal to distal. In other embodiments, the outer surface of the distal tip 47 may not be fully convex. For example, the distal tip 47 may have a convex outer surface with grooves that extend along a plane that includes the axis BB of the central body 31 and define a flow directing channel that extends toward the apex, i.e., most downstream point, of the distal tip 47 of the central body 31.

[0058] An exemplary embodiment of a distal tip having a grooved outer surface is shown in Figure 9. The central body 31 of Figure 9 can be used in any one of the previously described embodiments. A groove or channel along the outer surface of the distal tip of the central body 31 is labeled with the numeral 61. In the exemplary embodiment of Figure 9, the groove 61 extends from a first end 61A located along the maximum circumference of the distal tip 47 to a second end 61B located at the apex V of the distal tip 47. Other embodiments may include shorter grooves.

[0059] In the embodiment of FIG. 9, the distal tip 47 remains broadly convex, tapering from a larger section facing the proximal end of the central body 31 to a narrower section at the apex V of the distal tip 47.

[0060] A further embodiment of a fuel injector and fuel nozzle according to the present disclosure is shown in Figure 10. Reference numbers that are the same as those used in Figures 1 to 9 indicate the same or similar parts or components, which will not be described again.

[0061] To further improve flame control, according to the embodiment of Figure 10, in addition to the fuel ducts terminating in the fuel injection ports 57, the centerbody 31 further features additional fluid conduits extending along the centerbody 31 and terminating in one or more exit ports at the distal tip or downstream end 33 of the centerbody 31. In the embodiment of Figure 10, the additional fluid conduits are labeled 71 and the exit ports are labeled 73.

[0062] 10, the additional fluid conduit 71 has a single outlet port 73 located at the top of the dome-shaped distal tip 47. In a further embodiment not shown, the additional fluid conduit 71 may be fluidly coupled to multiple outlet ports 73, preferably located at axisymmetric positions about the axis BB of the central body 31. In yet another embodiment (not shown), two or more additional fluid conduits 71 may be provided within the central body 31, each conduit being fluidly coupled to one or more outlet ports.

[0063] The outlet port 73 can be circular. In other embodiments, for example, if the port is disposed about the axis BB of the central body 31, the outlet port 73 can have a tangentially elongated shape about the axis BB of the central body 31, or can be longitudinally elongated.

[0064] In some embodiments, the additional fluid conduit 71 is coupled to a fluid source, indicated generally at 75, or to two fluid sources, indicated at 75 and 77. In some presently preferred embodiments, the fluid source 75 may be a combustion air source. In other embodiments, the fluid source 75 may be a fuel source. When two fluid sources 75, 77 are provided, one fluid source may be an air fluid source and the other may be a fuel source.

[0065] Control valves 79, 81 may be provided to control fluid flow to and through one or more additional fluid conduits 71. For example, one valve 79 may be provided to control the flow of additional combustion air from source 75 to one or more outlet ports 73. A valve 81 may be provided to control the flow of additional fuel from source 77 to one or more outlet ports 73.

[0066] In some embodiments, when two or more additional fluid conduits 71 are provided within the central body 31, at least one of them may be fluidly coupled to a combustion air source and the other may be fluidly coupled to a fuel source.

[0067] To provide additional means of controlling the flame shape, additional combustion air, additional fuel, or a mixture of air and fuel can be delivered through additional fluid conduits to the distal tip of the central body 31. Depending on the operating conditions of the combustor 7, additional combustion air and / or fuel can be delivered to the distal tip of the central body 31 to provide optimal control of the combustion process, improve flame shape and positional stability, and prevent the flame from attaching to the distal tip of the central body 31, i.e., the burner.

[0068] Furthermore, the additional fluid conduits prevent flame ignition in low velocity regions and reduce the risk of acoustic interactions. Enhanced thermoacoustic response and reduced emissions are achieved, as well as better control of wall tip temperatures and burner durability.

[0069] A further embodiment of a fuel nozzle including multiple fuel injectors is shown in Figure 11. The same reference numbers in Figure 11 indicate the same or equivalent components already described in relation to the previous Figures 1 to 10, which will not be described in detail again. In the embodiment of Figure 11, each central body 31 has an internal partition wall 101 that divides the hollow space within the central body 31 into a first internal volume 32A in the extension of the respective fuel infeed chamber 21 and a second internal volume 32B extending from the partition wall 101 to a distal tip. One or more fuel injection ports 57 extend from the first internal volume 32A to the annular premix chamber 43 to deliver a flow of fuel from the fuel infeed chamber 21 towards the annular premix chamber 43, where the fuel is mixed with air flowing through an air inlet port 41 provided in the generally cylindrical wall of the outer sleeve 35.

[0070] In FIG. 11 , only one fuel injection port 57 is shown, however, it will be understood that two or more fuel injection ports 57 may be provided, preferably disposed circumferentially about the axis BB of the central body 31.

[0071] The second interior volume 32B is in fluid communication with at least one additional fluid conduit 71. An outlet port 73 at the outermost end of the distal tip 47 provides fluid communication between the second interior volume 32B and the combustion chamber 11.

[0072] As discussed above with respect to FIG. 10 , the additional fluid conduit 71 may deliver additional air flow, or additional fuel flow, or a mixture of additional fuel and air flow, toward the distal tip 47 through an exit port 73 in the central body 31 .

[0073] Yet another embodiment of a fuel nozzle including multiple fuel injectors is shown in Figures 12 and 13. The same reference numbers are used to designate the same elements as those shown in the previously described figures, and they will not be described again. The embodiment of Figures 12 and 13 differs from the embodiment of Figure 11 mainly in that multiple outlet ports 73 are provided at the distal tip 47 of the central body 31. More specifically, a central outlet port 73A is located at the center of the distal tip 47 on the axis of the central body 31. A first set of additional outlet ports 73B is distributed along a first circumference about the axis of the central body 31. A second set of additional outlet ports 73C is distributed along a second circumference about the axis of the central body 31. The ports 73A, 73B, 73C may have the same cross section, e.g. circular. In other embodiments, the ports may have cross sections of variable size and / or shape. The location of the ports and the number of circular arrangements of said ports may also be varied according to design options.

[0074] Exemplary embodiments are disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various modifications, omissions, and additions may be made to what is specifically disclosed herein without departing from the scope of the invention as defined in the following claims.

Claims

1. 1. A fuel injector for a gas turbine engine, comprising: a fuel feed chamber having an end wall; a central body extending along a longitudinal axis from the end wall to a distal end of the central body; an outer sleeve surrounding the central body and extending along the longitudinal axis of the central body from the end wall to a distal end of the outer sleeve opposite the fuel feed chamber; an annular premix chamber between the outer sleeve and the central body, the annular premix chamber having an annular outlet at the distal end of the outer sleeve; at least one air inlet port extending through the outer sleeve and in fluid communication with the annular premix chamber; a fuel conduit within the center body in fluid communication with the fuel infeed chamber and the annular premixing chamber; the central body includes a distal tip that projects outside the annular premix chamber beyond the distal end of the outer sleeve, the distal tip having a convex outer surface having a tapered shape; 1. A fuel injector comprising: a central body comprising a first portion proximate the end wall of the fuel feed chamber and extending toward the distal tip of the central body; and a second portion intermediate the first portion and the distal tip, wherein the first portion has a cylindrical shape with a circular cross section, and the second portion has a circular cross section and a diameter that increases from the first portion toward the distal tip, and has a maximum diameter at the distal end of the outer sleeve or outside the distal end of the outer sleeve.

2. The fuel injector of claim 1 , wherein the convex outer surface of the distal tip is a surface of revolution coaxial with the centerbody.

3. The fuel injector of claim 1 , wherein the distal tip has one of a dome shape, a spherical cup shape, a hemispherical shape, and an ogive shape.

4. The fuel injector of claim 1 , wherein the annular premix chamber has a converging distal portion having a cross-sectional area that tapers in a proximal to distal direction to the annular exit of the annular premix chamber.

5. The fuel injector of claim 1, wherein the first portion of the central body has a constant diameter.

6. 2. The fuel injector of claim 1, wherein the centerbody has a main portion inside the annular premix chamber, the main portion and the distal tip being connected by a smooth transition zone that tapers toward the distal end of the centerbody.

7. 2. The fuel injector of claim 1, wherein the centerbody has a main portion inside the annular premix chamber, the main portion connected to the distal tip along a transition zone that converges toward the distal end of the centerbody, the transition zone being defined by a surface generated by a generator line having continuous derivatives.

8. The central body comprises an axially extending outer tubular wall and an axially extending inner tubular wall, the fuel conduit extends from the fuel infeed chamber along an axial cavity in the inner tubular wall toward the distal end of the center body, and extends from the distal end of the center body toward the fuel infeed chamber along an annular gap formed between the outer tubular wall and the inner tubular wall; The fuel injector of claim 1 , wherein said outer tubular wall defines at least one fuel injection port fluidly connecting said fuel conduit and said annular premix chamber.

9. The fuel injector of claim 1 , wherein the centerbody and the outer sleeve are coaxial.

10. The fuel injector of claim 1 , wherein the centerbody and the outer sleeve are non-coaxial and the annular premix chamber has a radial dimension that varies about the longitudinal axis of the centerbody.

11. The fuel injector of claim 1 , wherein the central body includes at least one additional fluid conduit extending therealong and fluidly coupled to at least one outlet port at the distal tip of the central body.

12. The fuel injector of claim 11 , wherein the additional fluid conduit is adapted to deliver at least one of the following to the at least one outlet port: combustion air, fuel, or an air / fuel mixture.

13. The fuel injector of claim 11 , wherein the at least one outlet port is positioned on the longitudinal axis of the centerbody.

14. The fuel injector of claim 11 , comprising a plurality of outlet ports fluidly coupled to the additional fluid conduit and distributed according to a circular arrangement about the longitudinal axis of the central body.

15. 12. The fuel injector of claim 11, comprising a further fluid conduit extending along the central body and fluidly coupled to at least a further outlet port at the distal end of the central body, the further fluid conduit adapted to deliver fuel to the further outlet port.

16. A fuel injector as described in claim 1, wherein the distal tip of the central body has a groove extending toward a downstream-most point of the distal tip of the central body.

17. A fuel injector as described in claim 1, wherein the maximum diameter of the central body is smaller than the inner diameter of the outer sleeve, and / or the central body has its maximum diameter at the distal end of the outer sleeve or near the outside of the distal end of the outer sleeve.

18. A fuel nozzle for a gas turbine engine, comprising at least one fuel injector according to any one of the preceding claims.

19. The fuel nozzle of claim 18 , wherein the fuel nozzle comprises a plurality of fuel injectors.

20. The fuel nozzle of claim 19 , further comprising a front wall, the outer sleeve of the fuel injector being connected to the front wall.

21. The fuel nozzle of claim 19 , wherein the fuel injectors are parallel to one another.

22. The fuel nozzle of claim 19 , wherein at least two of the fuel injectors have converging axes.

23. A fuel nozzle as described in claim 19, wherein at the distal end of the outer sleeve, each of the central bodies is non-coaxially positioned relative to the axis of the outer sleeve so as to be closer to the center of the multiple fuel injectors.

24. 1. A combustor assembly for a gas turbine engine, comprising: a combustion chamber extending from an upstream end to a downstream end, the downstream end adapted to be fluidly coupled to a turbine section of the gas turbine engine and the upstream end adapted to be fluidly coupled to an air compressor of the gas turbine engine; At least one fuel nozzle according to claim 18; a fuel delivery duct fluidly coupled to the fuel injector of the fuel nozzle.

25. A gas turbine engine comprising the combustor assembly of claim 24.

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