Combustor unit, gas turbine assembly and method for controlling fuel injection

Abstract

A combustor unit (10) for a gas turbine assembly (1) comprising a premix combustor (15) and a reheat combustor (16) arranged in series along an airflow direction (M); the reheat combustor (16) comprising: a casing (20) extending substantially along a longitudinal axis (B) and defining a reheat combustion chamber (23), a plurality of injection units (27) distributed around the reheat combustion chamber (23) and fed with air and fuel; at least a first injection unit (27a) of the plurality of injection units (27) being configured to inject fuel and air differently with respect to the other injection units (27b, 27c, 27d, 27e).

Description

[0001] Cross-reference to related applications

[0002] This patent application claims priority to European Patent Application No. 20217211.0, filed on 24 December 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to burner units for gas turbine assemblies and, in particular, gas turbine assemblies for power plants (sometimes also called power generators).

[0004] The present invention also relates to a method for controlling fuel injection in a burner unit. Background Technology

[0005] As is well known, gas turbine components used in power equipment include compressors, combustor units, and turbines.

[0006] Specifically, the compressor includes an inlet that supplies air and multiple blades that compress the air passing through. Compressed air leaving the compressor flows into a pressurization chamber, a closed volume, and from there into a combustor unit, where it mixes with at least one fuel and burns. The resulting hot gas leaves the combustor unit and expands in a turbine, producing mechanical work.

[0007] High turbine inlet temperature is required to achieve high efficiency.

[0008] However, this high temperature results in high NOx emissions.

[0009] To reduce these emissions and increase operational flexibility, gas turbine assemblies have been developed, which include combustor units that perform sequential combustion cycles.

[0010] Typically, a sequential burner unit comprises two burners connected in series, each with its own burner and combustion chamber. Along the main airflow direction, the upstream burner, referred to as the "premixed" burner, is supplied with compressed air. The downstream burner, referred to as the "sequential" or "reheat" burner, is supplied with hot gas exiting the first combustion chamber.

[0011] According to the first known configuration, the two combustors are physically separated by a high-pressure turbine. Along the main airflow, the first configuration includes a compressor, a premixed combustor, a high-pressure turbine, a reheat combustor, and a low-pressure turbine.

[0012] According to the second known configuration, the premixed burner and the reheat burner are arranged directly downstream of each other within a common housing, specifically a cylindrical housing, and no high-pressure turbine is used. With this sequential gas turbine, multiple cylindrical burners are arranged, distributed around the turbine axis.

[0013] Each reheat burner preferably includes a reheat burner and a reheat combustion chamber into which the premixed hot flow is discharged. A transition duct is arranged downstream of the reheat combustion chamber and directs the hot gas leaving the reheat burner to the turbine.

[0014] A reheat burner may include multiple identical injection units arranged circumferentially around the reheat combustion chamber and designed to inject fuel uniformly into the reheat combustion chamber.

[0015] Under certain operating conditions, the reheat burner flame generates self-excited thermoacoustic pulsations that may exceed acceptable pulsation limits and unnecessarily restrict the operating range of the gas turbine.

[0016] To address this, burner assemblies are typically equipped with suppression devices to dampen these pressure oscillations. However, these suppression devices are not always effective and require space, and are not always available in all burner assemblies. Summary of the Invention

[0017] Therefore, the main objective of this invention is to provide a burner unit in which flame pulsation is reduced in a cost-effective manner without affecting NOx emissions.

[0018] According to the present invention, this objective is achieved by a combustor unit for a gas turbine assembly, the combustor unit comprising a premixed combustor and a reheat combustor arranged in series along the airflow direction;

[0019] The reheat burner includes:

[0020] • The shell generally extends along the longitudinal axis and defines the reheat combustion chamber.

[0021] • Multiple injection units distributed around the reheat combustion chamber and supplied with air and fuel;

[0022] • At least one of the multiple injection units is configured to inject fuel and air differently from the other injection units.

[0023] By designing the injection unit according to the non-uniform distribution pattern, flame behavior is controlled and instability is prevented or reduced when operating conditions that are prone to undesirable thermoacoustic pulsations occur.

[0024] In fact, the non-uniformity of the injection unit will cause a non-uniform distribution of flame characteristics (local delay time, flame front, etc.). Thus, thermoacoustic pulsation will not only not increase, but will also decrease due to destructive interference.

[0025] According to a variant, all the injection units in the multiple injection units are configured to inject fuel and air differently from each other.

[0026] According to a variant of the invention, at least one of the plurality of injection units is configured to inject fuel and air into the reheat combustion chamber according to different stoichiometric ratios and / or different mixtures between air and fuel and / or different penetrations relative to the other injection units.

[0027] According to another variation of the invention, the geometry of at least one first injection unit among the plurality of injection units is different from the geometry of the other injection units among the plurality of injection units.

[0028] According to a variation of the invention, the amount of air and / or fuel supplied to at least one first injection unit among a plurality of injection units is different from the amount of air and / or fuel supplied to the other injection units among the plurality of injection units.

[0029] According to a variation of the invention, each of the plurality of injection units engages a corresponding hole in the housing.

[0030] According to a variant of the invention, each of the plurality of injection units includes a fuel supply line and at least one fuel nozzle in fluid communication with the fuel supply line; an air supply line and at least one air nozzle in fluid communication with the air supply line; a delivery pipe extending along an extension axis and having an outlet for flowing into a reheat combustion chamber; in the delivery pipe, air and fuel from at least one fuel nozzle and an air nozzle are mixed.

[0031] According to another variation of the invention, the inlet of the delivery pipe coincides with the air nozzle.

[0032] According to a variation of the invention, at least one first injection unit has a delivery pipe, the length of which differs from the length of the delivery pipes of the other injection units.

[0033] Preferably, according to an embodiment of the present invention, the first diameter of at least one first fuel nozzle of at least one first injection unit is different from the diameter of the fuel nozzle of other injection units.

[0034] According to another embodiment of the present invention, at least one first injection unit has a first delivery pipe, the first pipe width of which is different from the pipe width of the delivery pipes of the other injection units.

[0035] According to another embodiment of the present invention, at least one first injection unit has a first air nozzle, the channel cross-section of which is different from the channel cross-section of the air nozzles of other injection units.

[0036] According to another embodiment of the present invention, the first injection unit includes a metering plate having holes and being connected to a first air nozzle to adjust the channel cross-section of the first air nozzle.

[0037] According to another embodiment of the invention, at least the first injection unit has a first delivery pipe extending along an extension axis, which is inclined differently from the extension axes of the delivery pipes of the other injection units.

[0038] Another object of the present invention is to provide a gas turbine assembly in which flame pulsation is reduced in a cost-effective manner without affecting NOx emissions.

[0039] For these purposes, the present invention relates to a gas turbine assembly as described in claim 15. Attached Figure Description

[0040] To better understand the present invention and its advantages, an exemplary embodiment of the present invention will be described below with reference to the accompanying drawings, wherein:

[0041] - Figure 1 This is a schematic diagram of a gas turbine assembly equipped with a burner unit according to the invention, wherein components have been removed for clarity;

[0042] - Figure 2a This is a schematic side cross-sectional view of a burner unit according to the present invention, wherein components have been removed for clarity;

[0043] - Figure 2b yes Figure 2a Enlarged view of the details;

[0044] - Figures 3a-3c This is a schematic enlarged cross-sectional view of the burner unit in Figure 2;

[0045] - Figures 4a-4c This is a schematic enlarged cross-sectional view of the burner unit of FIG2 according to a first variant of the present invention;

[0046] - Figures 5a-5c This is a schematic enlarged cross-sectional view of the burner unit of FIG2 according to a second variant of the present invention;

[0047] - Figures 6a-6c This is a schematic enlarged cross-sectional view of the burner unit of FIG2 according to a third variant of the present invention. Detailed Implementation

[0048] Figure 1 This is a schematic diagram of a gas turbine assembly 1 for a power device according to the present invention.

[0049] The gas turbine assembly 1 includes a compressor 2, a burner assembly 3, and a turbine 4. The compressor 2 and the turbine 4 have a common axis A and form corresponding portions of a rotor 5 that can rotate about axis A.

[0050] As is well known, ambient air 6 enters compressor 2 and is compressed. Compressed air 7 exits compressor 2 and enters pressurization chamber 8, which is the volume defined by housing 9. From pressurization chamber 8, compressed air 7 enters combustor assembly 3, which includes a plurality of combustor units 10 arranged annularly around axis A. Combustor unit 10 is generally defined as a "canister combustor". In combustor unit 10, at least fuel is injected and the air / fuel mixture is ignited, producing hot gas 11 delivered to turbine 4.

[0051] like Figure 2a As better illustrated, each burner unit 10 is housed in a corresponding inlet port of the housing 9 and has an axis B. The burner unit 10 includes a first or premixed burner 15, a second or reheat burner 16, and a transition duct 19 connected in series along the airflow M, which directs the hot gas exiting the reheat burner 16 to the turbine 4.

[0052] Specifically, the premixed burner 15 includes a premixed burner 17 and a first combustion chamber 18.

[0053] The reheat burner 16 includes a housing 20 that defines the combustion chamber 23 and the reheat burner 22.

[0054] Preferably, the housing 20 is a double-walled housing, wherein a cooling gap 24 is formed (in Figures 3a-3c (More clearly visible in 4a-4c, 5a-5c, 6a-6c). The cooling gap 24 is supplied with air from the pressurization chamber 8.

[0055] The housing 20 is arranged inside the outer casing 25, which substantially surrounds the housing 20 to form an air chamber 26, which is supplied with air from the pressurization chamber 8.

[0056] refer to Figure 2b The reheat burner 22 includes multiple injection units, collectively designated as 27, and separately designated as 27a, 27b, 27c, 27d, etc.

[0057] Multiple injection units 27 are arranged around the reheat combustion chamber 23 and are supplied with air and fuel. Preferably, the multiple injection units 27 are arranged circumferentially around the reheat combustion chamber 23.

[0058] Each injection unit 27a, 27b, 27c, 27d, etc., engages with a corresponding through hole 28 formed in the housing 20.

[0059] refer to Figures 3a-3cEach injection unit 27a, 27b, 27c, 27d includes a fuel supply line 30 and at least one fuel nozzle 31 in fluid communication with the fuel supply line 30, an air supply line 29 and at least one air nozzle 32 in fluid communication with the air supply line 29, and a delivery line 33, wherein air and fuel from at least one fuel nozzle 31 and air nozzle 32 are mixed.

[0060] The delivery pipe 33 extends along axis C. In the non-limiting example disclosed and illustrated herein, the delivery pipe 33 extends from an inlet that coincides with the air nozzle 32 to an outlet 35 that flows into the reheat combustion chamber 23.

[0061] Preferably, the delivery pipe 33 is cylindrical and is at least partially housed in the hole 28 of the housing 20.

[0062] The air supply line 29 includes an air chamber 26 that surrounds the housing 20 and supplies all air nozzles 32.

[0063] The fuel supply line 30 includes a fuel conduit 37 (illustrated) and a fuel collector 38, preferably surrounding the inlet portion of the delivery pipe 33. The fuel supplied to the fuel supply line 30 may be the same fuel supplied to the first burner 15 or a different fuel.

[0064] In the non-limiting examples disclosed and illustrated herein, each injection unit 27a, 27b, 27c, 27d, 27e includes a plurality of fuel nozzles 31 arranged along a generally circumferential path extending in a plane orthogonal to axis C.

[0065] At least one of the plurality of injection units 27a is configured to inject fuel and air differently from the other injection units of the plurality of injection units 27.

[0066] The expression “differently” means that the geometry or supply control of the air and / or fuel is different from the geometry or supply control of the other injection units 27b, 27c, 27d, 27e in the plurality of injection units 27.

[0067] Preferably, the injection unit 27a is configured to inject fuel and air according to different equivalence ratios and / or different mixtures between air and fuel and / or different penetrations into the reheat combustion chamber 23 relative to other injection units 27b, 27c, 27d, 27e among the plurality of injection units 27.

[0068] The expression "equivalent ratio" refers to a ratio. It is defined according to the following formula:

[0069]

[0070] It is the ratio of fuel-air ratio to stoichiometric fuel-air ratio.

[0071] The advantage of using an equivalence ratio instead of a fuel-air ratio is that it takes into account (and is therefore independent of) both the mass and molar value of fuel and air.

[0072] The phrase "mixing between air and fuel" refers to the way fuel and air supplied to the injection unit are mixed (e.g., with the presence of a vortex generator / deflector and other devices for controlling the mixing between fuel and air).

[0073] The phrase "penetration into the reheat combustion chamber" refers to the jet characteristics of the air-fuel mixture injected into the reheat combustion chamber 23. Specifically, the jet characteristics of the air-fuel mixture can depend on the jet flow rate, jet diameter, jet angle, and the location where the air-fuel mixture from the injection unit is injected into the reheat combustion chamber 23.

[0074] In this way, at least one non-uniformity is introduced into the reheat combustion chamber 23. This results in a non-uniform distribution of the flow field and the hot gas, fuel, and air mixing field in the reaction zone (flame) of the reheat burner 16. As a result, acoustic dynamics are suppressed and some of the risk of increased acoustic oscillations is avoided.

[0075] exist Figures 3a-3c The first embodiment of the invention is illustrated in the figure, wherein at least the injection unit 27a has a delivery pipe 33a, the length La of which is different from the lengths Lb, Lc, Ld, Le of the delivery pipes 33b, 33c, 33d, 33e of the other injection units 27b, 27c, 27d, 27e. The pipe length is measured along the axis C.

[0076] Preferably, the pipe length La is greater than the pipe lengths Lb, Lc, Ld, Le of the delivery pipes 33b, 33c, 33d, 33e of the other injection units 27b, 27c, 27d, 27e.

[0077] More preferably, the tube length La is greater than the depth of the shell 20.

[0078] According to a variant not shown, the tube lengths La, Lb, Lc, Ld, Le are different from each other to change the penetration depth of each injection unit 27.

[0079] exist Figures 4a-4c The second embodiment of the present invention is shown in the figure, wherein at least the injection unit 27a has a fuel nozzle 31a, the diameter Da of which is different from the diameters Db, Dc, Dd, De of the fuel nozzles 31b, 31c, 31d, 31e of the other injection units 27b, 27c, 27d, 27e.

[0080] Preferably, the diameter Da of the fuel nozzle 31a is larger than the diameters Db, Dc, Dd, De of the fuel nozzles 31b, 31c, 31d of the other injection units 27b, 27c, 27d, 27e.

[0081] According to a variant not shown, the diameters Da, Db, Dc, Dd, De of the fuel nozzles 31a, 31b, 31c, 31d, 31e are different from each other to change the equivalence ratio and the mixing between air and fuel in each injection unit 27.

[0082] exist Figures 5a-5c The third embodiment of the invention is shown in the figure, wherein at least the injection unit 27a has a delivery pipe 33a, the width Wa of which is different from the widths Wb, Wc, Wd, and We of the delivery pipes 33b, 33c, 33d, and 33e of the other injection units 27b, 27c, 27d, and 27e. The pipe width is measured in a direction orthogonal to the axis C.

[0083] Preferably, the pipe width Wa is smaller than the pipe widths Wb, Wc, Wd, We of the delivery pipes 33b, 33c, 33d, 33e of the other injection units 27b, 27c, 27d, 27e.

[0084] According to a variant not shown, the pipe widths Wa, Wb, Wc, Wd, and We are different from each other to change the equivalence ratio and the mixing between air and fuel in each injection unit 27 as well as the penetration into the reheat combustion chamber 23.

[0085] exist Figures 6a-6c The fourth embodiment of the present invention is shown in the figure, wherein at least the injection unit 27a has an air nozzle 32a, the channel cross section Aa of which is different from the channel cross sections Ab, Ac, Ad, Ae of the air nozzles 32b, 32c, 32d, 32e of the other injection units 27b, 27c, 27d, 27e.

[0086] Preferably, the air nozzle 32a has a smaller channel cross section Aa than the channel cross sections Ab, Ac, Ad, Ae of the air nozzles 32b, 32c, 32d, 32e of the other injection units 27b, 27c, 27d, 27e.

[0087] More preferably, the air nozzle 32a is connected to a metering plate 39 having a hole 40, the channel cross-section of which is the desired Aa.

[0088] According to a variant not shown, the cross-sectional areas Aa, Ab, Ac, Ad, and Ae of the air nozzles 32a, 32b, 32c, 32d, and 32e of the injection units 27a, 27b, 27c, 27d, and 27e are different from each other to change the equivalence ratio and the air-fuel mixture of each injection unit 27.

[0089] In the example disclosed and illustrated herein, all delivery pipes 33a, 33b, 33c, 33d, 33e extend along axis B, which is arranged substantially radially relative to axis B of burner unit 10.

[0090] According to a variant not shown, at least one of the injection units 27a, 27b, 27c, 27d, 27e is provided with a delivery pipe 33a, 33b, 33c, 33d, 33e extending along a non-radial axis.

[0091] According to another variant, all the delivery pipes 33a, 33b, 33c, 33d, and 33e extend along their respective axes, which are not arranged radially and are inclined differently from each other.

[0092] According to a variant not shown, at least one of the injection units 27a is provided with a fuel nozzle 31a, the shape and / or position of which differs from the shape and / or position of the other fuel nozzles 31b, 31c, 31d, 31e.

[0093] According to another variant not shown, the fuel nozzles 31a, 31b, 31c, 31d, 31e have different shapes and / or positions to change the equivalence ratio and the mixing between air and fuel in each injection unit 27.

[0094] According to a variant not shown, the supply line 30 can be adjusted to supply different fuel flow rates to at least one of the plurality of injection units 27. For example, the cross-sectional area of ​​the fuel conduit 37 of at least one injection unit 27a may be different from the cross-sectional area of ​​the fuel conduit 37 of at least one injection unit 37b, 37c, 37d, 37e.

[0095] According to another variant not shown, at least one of the plurality of injection units 27 is provided with a combination of the different features described above for each embodiment.

[0096] Further variations could be considered and focused on that could modify the geometry of the injection unit, which is capable of altering the stoichiometric ratio and / or the air-fuel mixture and / or the penetration into the reheat combustion chamber 23.

[0097] In this way, the different behaviors of the jet nozzles will produce inhomogeneities at the flame front, and thus cause destructive interference with acoustic oscillations.

[0098] Although the invention has been explained in conjunction with its preferred embodiments described above, it should be understood that many other possible modifications and variations may be made without departing from the scope of the appended claims.

Claims

1. A combustor unit (10) for a gas turbine assembly (1), comprising a premixed combustor (15) and a reheat combustor (16) arranged in series along the airflow direction (M); said reheat combustor (16) comprising: The shell (20) generally extends along the longitudinal axis (B) and defines the reheat combustion chamber (23). Multiple injection units (27) are distributed around the reheat combustion chamber (23) and supplied with air and fuel; At least one first injection unit (27a) of the plurality of injection units (27) is configured to inject fuel and air differently from the other injection units (27b, 27c, 27d, 27e); wherein the at least one first injection unit (27a) of the plurality of injection units (27) is configured to inject fuel and air according to different equivalence ratios and / or different mixing between air and fuel and / or different penetration into the reheat combustion chamber (23) relative to the other injection units (27b, 27c, 27d, 27e); wherein each injection unit (27a, 27b, 27c, 27d, 27e) of the plurality of injection units (27) engages a corresponding hole (28) in the housing (20); Each of the plurality of injection units (27) includes: a fuel supply line (30) and at least one fuel nozzle (31) in fluid communication with the fuel supply line (30); an air supply line (29) and at least one air nozzle (32) in fluid communication with the air supply line (29); and a delivery pipe (33) extending along an extension axis (C) and provided with an outlet (35) flowing into the reheat combustion chamber (23); in the delivery pipe (33), air and fuel from the at least one fuel nozzle (31) and the air nozzle (32) are mixed; wherein the inlet of the delivery pipe (33) coincides with the air nozzle (32).

2. The burner unit of claim 1, wherein, All of the multiple injection units (27) (27a, 27b, 27c, 27d, 27e) are configured to inject fuel and air differently from each other.

3. The burner unit according to any one of the preceding claims, wherein, The geometry of at least one first injection unit (27a) among the plurality of injection units (27) is different from the geometry of the other injection units (27b, 27c, 27d, 27e) among the plurality of injection units (27).

4. The burner unit according to claim 1 or 2, wherein, The amount of air and / or fuel supplied to at least one first injection unit (27a) of the plurality of injection units (27) is different from the amount of air and / or fuel supplied to the other injection units (27b, 27c, 27d, 27e) of the plurality of injection units (27).

5. The burner unit according to claim 1, wherein, The at least one first injection unit (27a) has a delivery pipe (33a) having a pipe length (La) different from the pipe length (Lb, Lc, Ld, Le) of the delivery pipes (33b, 33c, 33d, 33e) of the other injection units (27b, 27c, 27d, 27e).

6. The burner unit according to claim 1, wherein, At least one first fuel nozzle (31a) of the at least one first injection unit (27a) has a first diameter (Da) that is different from the diameter (Db, Dc, Dd, De) of the fuel nozzles (31b, 31c, 31d, 31e) of the other injection units (27b, 27c, 27d, 27e).

7. The burner unit according to claim 1, wherein the at least one first injection unit (27a) has a first delivery pipe (33a), the first delivery pipe (33a) having a first pipe width (Wa) different from the pipe width (Wb, Wc, Wd, We) of the delivery pipes (33b, 33c, 33d, 33e) of the other injection units (27b, 27c, 27d, 27e).

8. The burner unit according to claim 1, wherein, The at least one first injection unit (27a) has a first air nozzle (32a) having a channel cross section (Aa) different from the channel cross section (Ab, Ac, Ad, Ae) of the air nozzles (32b, 32c, 32d, 32e) of the other injection units (27b, 27c, 27d, 27e).

9. The burner unit according to claim 8, wherein, The at least one first injection unit (27a) includes a metering plate (39) having a hole (40) and being connected to the first air nozzle (32a) to adjust the channel cross section (Aa) of the first air nozzle (32a).

10. The burner unit according to claim 1, wherein, The at least one first injection unit (27a) has a first delivery pipe (33a) that extends along an extension axis (C) that is inclined differently from the extension axis (C) of the delivery pipes (33b, 33c, 33d, 33e) of the other injection units (27b, 27c, 27d, 27e).

11. A gas turbine assembly, comprising: The compressor (2), turbine (4), and burner assembly (3); the burner assembly (3) includes at least one burner unit (10) as described in any of the preceding claims.

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