Patent Application
20250109855
The subject matter disclosed herein generally relates to gas turbine engines. More particularly, the disclosure concerns a pre-mixing fuel nozzle for gas turbine engine combustors, as well as to gas turbine engine combustors including said pre-mixing fuels.
Gas turbine engines, for both aircraft and industrial applications, include at least one combustor in which fuel, either in gaseous or liquid form, is mixed with a compressed air stream and combusted to generate a flow of hot, pressurized combustion gas. The combustion gas is expanded in a turbine including one or more turbine stages to generate mechanical power. Part of the mechanical power generated by the turbine is used to drive the compressor of the gas turbine engine and to support continuous supply of combustion air to the combustor. The remaining available power is used to either to drive a load, such as an electric generator or a compressor, or to generate a thrust for aircraft propulsion.
The combustor includes a combustion chamber and a plurality of fuel nozzles, which feed a liquid or gaseous fuel into the stream of compressed air 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 feed of compressed air and fuel to the combustor, the combustion process is maintained to generate a continuous flow of compressed, hot combustion gas to operate the turbine.
Control of the flame in the combustor is one of the critical aspects of fuel nozzle design. One of the aims of nozzle design is reduction of noxious emissions, such as nitrogen oxides (NOx), carbon monoxide (CO) and unburned hydrocarbons (CxHy). Further points of concern are life-time requirements, in terms of thermal cycles which the burner can withstand prior to replacement, as well as the control of thermally induced deformations.
An improved fuel nozzle design aimed at addressing the above concerns would be welcomed in the art.
According to an aspect, disclosed herein is a fuel nozzle for a gas turbine, including a stem and a plurality of fuel injectors. The fuel nozzle includes a first fuel feed channel extending inside the stem from an inlet end, positioned at a proximal end of the stem, to a first fuel inlet plenum. A first set of fuel injectors are fluidly coupled to the first fuel inlet plenum and project at an angle from the stem. The fuel nozzle further includes a second fuel feed channel extending inside the stem, from an inlet end, positioned at the proximal end of the stem, to a second fuel inlet plenum. A second set of fuel injectors are fluidly coupled to the second fuel inlet plenum and projecting at an angle from the stem.
In embodiments disclosed herein, each fuel injector includes a centerbody extending along a longitudinal axis from the respective fuel inlet plenum to a distal end of the centerbody. An outer sleeve surrounds each centerbody and extends along the axis of the centerbody. An annular premix chamber is formed between each outer sleeve and the respective centerbody. At least one air inlet port extends through each outer sleeve, and at least one fuel conduit in each centerbody is in fluid communication with the respective fuel inlet plenum and the respective annular premix chamber.
The fuel nozzle including the above parts is manufactured as a single monolithic body or block, preferably by additive manufacturing, which allows complex shapes of the various components and elements to be manufactured with limited design constraints.
According to another aspect, disclosed herein is a combustor including a plurality of fuel nozzles as outlined above, as well as a gas turbine engine including the above-mentioned combustor.
Further features and embodiments will be described in greater detail in the following description, reference being made to the enclosed drawings, and are set out in the appended claims.
Reference is now made briefly to the accompanying drawings, in which:
Embodiments of the invention are suitable for all types of gas turbine engines, regardless of the end use application. Fuel injectors disclosed herein can be used in aeroderivative gas turbines, as well as industrial, heavy duty gas turbines. In the following description reference will be made to a gas turbine for mechanical drive, but those skilled in the art will understand that the fuel injectors of the present disclosure can be used also in gas turbines for electric generation, as well as for air propulsion.
While in the following description reference is made specifically to combustors including an annular combustion chamber, it shall be understood that fuel injectors and fuel nozzles including features of the present disclosure can be used also in other kinds of combustors, including can combustion chambers or tubo-annular combustion chambers, for instance.
Turning now to the drawings,
The gas turbine engine 1 includes an air compressor 5, a combustor 7 and a turbine section 9. By way of example only, in
The exemplary gas turbine engine of
According to some embodiments, the combustor 7 comprises an annular combustion chamber 11, as schematically shown in
One fuel nozzle 17 is shown in isolation in
For a better understanding of the shape and development of the plenums and of the channels extending along the stem of the nozzle,
The fuel nozzle 17 comprises a first portion extending along a direction X-X (see
In embodiments disclosed herein, the fuel nozzle includes a plurality of fuel injectors. In some embodiments the fuel nozzle includes four fuel injectors. More specifically, the fuel injectors include a first set of fuel injectors 21 which are fluidly coupled to a first fuel inlet plenum 25, and a second set of fluid injectors 23, which are fluidly coupled to a second fuel inlet plenum 27. In the exemplary embodiment shown in the drawings the first set of fluid injectors includes two fluid injectors 21 and the second set of fluid injectors includes two fluid injectors 23.
In the embodiment shown in the attached drawing, the fuel injectors 21 are arranged side-by-side on a plane O1 (see
Each fuel injector 21 includes a centerbody 31 extending along the longitudinal axis 21A of the respective fuel injector 21, i.e., parallel to the direction Y-Y. Each centerbody 31 extends from the first fuel inlet plenum 25 towards a distal end 31A of the centerbody. Each centerbody 31 is surrounded by an outer sleeve 33, which can be coaxial to the respective centerbody 31. In some embodiments, the centerbody 31 and the outer sleeve 33 are non-coaxial but still arranged one inside the other. Irrespective of whether the centerbody 31 and the outer sleeve 33 are coaxial or non-coaxial, an annular premix chamber 35 forms therebetween, see in particular
Each outer sleeve 33 is provided with at least one air inlet port 34, and preferably with a plurality of air inlet ports 34, which extend through the outer sleeve 33, i.e., through the wall forming the outer sleeve 33, from the exterior of the outer sleeve 33 to the annular premix chamber 35. Several air inlet ports 34 can be provided, each with its own inclination with respect to the axis of the centerbody 31. While in the attached drawings the air inlet ports 34 have an axial orientation, which is substantially orthogonal to the axis of the centerbody, in other embodiments the air inlet ports may be oriented differently, with a constant inclination different from 90° with respect to the axial direction, or even with an inclination that can vary from one air inlet port to the other, for instance in order to provide an air swirl in the premix chamber. For instance, the air inlet ports 34 with the same inclination may be grouped and different groups of air inlet ports 34 with different inclinations may be distributed in various regions of the outer sleeve 33.
Similarly, each fuel injector 23 includes a centerbody 37 extending along the longitudinal axis 23A of the respective fuel injector 23, i.e., parallel to the direction Y-Y. Each centerbody 37 extends from the second fuel inlet plenum 27 towards a distal end 37A of the centerbody. Each centerbody 37 is surrounded by an outer sleeve 39, which can be coaxial to the respective centerbody 37. In some embodiments, the centerbody 37 and the outer sleeve 39 are non-coaxial but still arranged one inside the other. Irrespective of whether the centerbody 37 and the outer sleeve 39 are coaxial or non-coaxial, an annular premix chamber 41 forms therebetween, see in particular
Each outer sleeve 39 is provided with at least one air inlet port 40, and preferably with a plurality of air inlet ports 40, which extend through the outer sleeve 39, i.e., through the wall forming the outer sleeve 39, from the exterior of the outer sleeve 39 to the annular premix chamber 41. As mentioned above in connection with the air inlet ports 34, also the air inlet ports 40 may have a different inclination, for instance, they can be non-orthogonal to the axis of the centerbody, and may have inclinations which vary from one air inlet port to the other.
Each outer sleeve 33, 39 extends from a lower portion 19B of the stem 19 to a front wall 45 which mechanically connects the distal ends of all outer sleeves 33, 39 to one another. The front wall 45 has a front surface 45A which, when the fuel nozzle 17 is mounted in the combustor, faces the interior of the combustion chamber 11. The front wall 45 further includes a side surface 45B, which forms an edge surrounding the front wall. The edge may include two parallel straight edge portions, which are parallel to the direction X-X, i.e., substantially parallel to the stem 19. The straight edge portions allow a plurality of fuel nozzles 17 to be placed side-by side around the annular extension of the combustion chamber 11, thus closing the combustion chamber 11. With this configuration, a large number of adjacent fuel injectors can be arranged in a small space at the upstream end of the combustion chamber 11 around the axis A-A thereof.
In embodiments disclosed herein, each centerbody 31 of the fuel injectors 21 includes at least one fuel conduit 51, which is in fluid communication with the first fuel inlet plenum 25. In the embodiment shown in the attached drawings, a plurality of fuel conduits 51 are arranged around the longitudinal axis of each centerbody 31. The fuel conduits 51 may be oriented with different inclinations over the axis of the centerbody. As mentioned in connection with the air inlet ports 34, also the fuel conduits 51 may be grouped in different groups of conduits, wherein the fuel conduits of each group have the same inclination and the inclination can differ from one group to another.
In use, fuel is delivered from the first fuel inlet plenum 23 through the fuel conduits 51 in the annular premix chamber 35, where fuel is mixed with air flowing into the premix chamber 35 through the air inlet ports 34 and forms an air-fuel mixture, which is delivered to the combustion chamber 11 and combusted therein.
Similarly, each centerbody 37 of the fuel injectors 23 includes at least one fuel conduit 53, which is in fluid communication with the second fuel inlet plenum 27. In the embodiment shown in the attached drawings, a plurality of fuel conduits 53 are arranged around the longitudinal axis of each centerbody 37. Fuel conduits 53 with different inclinations can be used as outlined above in connection with centerbodies 31.
In use, fuel is delivered from the second fuel inlet plenum 25 through the fuel conduits 53 in the annular premix chamber 41, where fuel is mixed with air flowing into the premix chamber 41 through the air inlet ports 40 and forms an air-fuel mixture, which is delivered to the combustion chamber 11 and combusted therein.
In some embodiments, each distal end 31A, 37A of the centerbodies 31, 37 projects beyond the front surface 45A of the front wall 45 towards the interior of the combustion chamber 11. In other embodiments, however, the centerbodies 31, 37 can be shorter such as not to project from the front surface 45A of the front wall 45.
In some embodiments, the distal ends 31A, 37A of each centerbody 31, 37 can be convex, e.g. hemi-spherical or in the form of an ogive. In other embodiments, the distal ends 31A 37A of the centerbodies 31, 37 can be shaped differently, i.e., they could be flat, or may be concave.
The front wall 45 has a plurality of apertures 45C, one for each fuel injector 21, 23. Since in the illustrated embodiment the centerbodies 31, 37 have distal ends 31A, 37A projecting beyond the front wall 45A, each aperture 45C forms, with the respective centerbody 31, 37, a circular or annular port, through which, in use, the air-fuel mixture formed in the respective premix chamber 35 and 41 flows into the combustion chamber 11.
In some embodiments, the fuel nozzle includes a third fuel inlet plenum 55. In embodiments, the third fuel inlet plenum 55 is housed in the front wall 45. The third fuel inlet plenum 55 will be referred to as pilot plenum.
As best shown in
The first fuel inlet plenum 25 is fluidly coupled to a source of fuel, not shown, through a first fuel feed channel 61, which extends from an inlet end 61A, located at the proximal end 19A of the stem 19, to the first fuel inlet plenum 25. The second fuel inlet plenum 27 is fluidly coupled to the source of fuel through a second fuel feed channel 63, which extends from an inlet end 63A, located at the proximal end 19A of the stem 19, to the second fuel inlet plenum 27. Finally, the pilot plenum 55 is fluidly coupled to the source of fuel through a third channel 65, which will be referred herein as a third fuel feed channel in connection with this embodiment. The third fuel feed channel 65 extends from an inlet end 65A, located at the proximal end 19A of the stem 19, to the pilot plenum 55. The amount of fuel delivered to the fuel inlet plenums may be adjusted individually for each inlet plenum by means of suitable control devices, such as controlled valves or the like, not shown. The fuel flowrate in each fuel inlet plenum can thus be adapted to the operating condition of the gas turbine engine.
The first fuel feed channel 61, the second fuel feed channel 63 and the third fuel feed channel 65 extend along the stem 19 and change shape and mutual position along their development, from the respective inlet ends 61A, 63A, 65A to the respective fuel inlet plenums 25, 27 and 55. The shape of each fuel feed channel 61, 63, 65 can be best appreciated from the sequence of axonometric sectional views of
At the proximal end 19A of the stem 19 the first fuel feed channel 61, the second fuel feed channel 63 and the third fuel feed channel 65 are arranged at the vertexes, i.e., at the corners of a triangle. Specifically, in the exemplary embodiment shown in the drawings, the first fuel feed channel 61 is arranged near an outer enveloping wall 69, which forms the outer skin of the stem 19 and within which the first fuel feed channel 61, the second fuel feed channel 63 and the third fuel feed channel 65 are enveloped.
The first fuel inlet channel 61 can be partly formed by the enveloping wall 69. The second fuel feed channel 63 can be connected to the enveloping wall 69 by a septum 71 and the third fuel feed channel 65 can be connected to the enveloping wall 69 by a septum 73.
Moreover, in some embodiments, the first fuel feed channel 61 can be connected to one or both the second fuel feed channel 63 and the third fuel feed channel 65. The first fuel feed channel 61 is mechanically coupled to the second fuel feed channel 63 by a septum 75 and is further mechanically coupled to the third fuel feed channel 65 by a further septum 77. The septa 75, 77 form two sides of the triangle, at the vertexes whereof the inlet ends 61A, 63A and 65A are positioned. Along the axial development of the stem 19 the shape and position of the septa change as a conse-quence of the changes in shape and position of the three fuel feed channels 61, 63, 65.
With this arrangement, the first fuel feed channel 61, the second fuel feed channel 63 and the third fuel feed channel 65 are rigidly coupled to one another and to the outer enveloping wall 69. The structure is rigid and can withstand mechanical stresses. At the same time, the septa 71, 73, 75, 77 and the outer enveloping wall 69, as well as the tubular structure of each fuel feed channel 61, 63, 65 are sufficiently thin to compensate for thermal expansions and contractions. Thermally induced stresses are thus reduced, which helps increasing the lifetime of the fuel nozzle 17.
Moving from the proximal end 19A towards the lower portion 19B of the stem 19, the shape and position of the first fuel feed channel 61, second fuel feed channel 6 and third fuel feed channel 65 change gradually, both with regard to the cross-sectional shape as well as with regard to the position of each channel with respect to the others and with respect to the outer enveloping wall 69.
More specifically, moving from the sectional plane of
In the sectional view of
From the position of
More specifically, the cross section of the first fuel inlet duct 61 expands until forming the first fuel inlet plenum 25 (
To provide further stiffness to the stem 19, in some embodiments one or more stiffening ribs 81 can be foreseen along the stem 19. In the embodiment shown in the drawings, the outer enveloping wall 69 comprises a pair of stiffening ribs 81 extending from an outer surface of the outer enveloping wall 69 and symmetrically arranged with respect to the median plane M-M of the stem 19.
The full structure of the fuel nozzle 17 described so far, including the stem 19, the front wall 45 and the fuel injectors 21, 23, can be formed as a single monolithic component, for instance by additive manufacturing.
While in the embodiments described above the third channel 65 is used as a fuel feed channel, in other embodiments, a third channel 65 can be a generic service channel, i.e., can be used for a different purpose, such as to provide a connection between an instrument, gauge, sensor, or any other functional component or feature, in-stalled on the fuel nozzle and in the exterior of the combustion chamber, in which the fuel nozzle is mounted.
According to some embodiments, the third channel 65 can be used to house the wiring of a sensor, such as a flame detector, a hummering sensor adapted to detect pressure variations, or other instrumentality. In some embodiments, the third channel 65 can be used to provide a wire connection to a spark plug, for instance.
Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the scope of the invention as defined in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022000001943 | Feb 2022 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/025048 | 2/2/2023 | WO |
