Combustor assembly and combustion chamber comprising same

Abstract

The invention relates to a burner assembly for a combustion chamber, provided with a pilot burner (2) extending along a longitudinal axis (A) and a premix burner (3) surrounding the pilot burner; the pilot burner (2) is integral with the premix burner (3).

Description

[0001] Priority declaration This application claims the benefit of European patent application 17155917.2 filed on February 13, 2017, the disclosure of which is incorporated by reference. Technical Field

[0002] The present invention relates to a burner assembly for a combustor of a gas turbine power station.

[0003] Furthermore, the present application relates to a combustion chamber comprising said burner assembly. Background Art

[0004] As is known, a gas turbine power plant (hereinafter simply referred to as a gas turbine plant) includes a rotor, which is provided with an air compressor; at least one combustion chamber, which is arranged downstream of the compressor and is supplied with air from the compressor; and at least one gas turbine, which is arranged downstream of the combustion chamber and is supplied with air that has undergone combustion from the combustion chamber.

[0005] In more detail, the compressor includes an inlet supplied with air and a plurality of blades and guide vanes configured to compress the air entering the compressor. The compressed air leaving the compressor flows into a plenum (sometimes also referred to as an air chamber) and from there into at least one burner assembly of the combustion chamber. Inside the burner assembly, the compressed air is mixed with at least one fuel. Such a mixture of fuel and compressed air is then burned. The resulting hot gases leave the combustion chamber cavity and expand in the turbine, performing work on the rotor.

[0006] The burner assemblies used in the last generation of gas turbine stations are preferably of the premix type, because they are characterized by low emissions. This type of burner assembly is known, for example, from the document US2007 / 0231762. The burner assembly comprises a premix burner and a pilot burner. The premix burner is configured to swirl the incoming combustion air and mix it with the fuel in the premixing zone.

[0007] The pilot burner includes a pilot lance centrally arranged in the burner assembly. At low operating loads, the pilot lance is configured to inject fuel axially into the combustion air to create a fuel-rich zone, ensuring that the flame does not extinguish. At higher operating loads, the injection of fuel via the pilot lance is reduced to reduce pollutants, and the injection of fuel via the premix burner is increased.

[0008] This known type of burner assembly has a structure made of a plurality of component parts that need to be assembled together. Therefore, the assembly of each burner assembly requires several steps and is therefore highly cumbersome. Summary of the invention

[0009] The object of the present invention is therefore to provide a burner assembly for a combustion chamber which allows the described disadvantages to be avoided or at least alleviated.

[0010] In particular, an object of the present invention is to provide a burner assembly which has a simplified structure so as to save assembly costs and which is sufficiently reliable at the same time.

[0011] According to the present invention, there is provided a burner assembly for a combustion chamber, which includes a pilot burner extending along a longitudinal axis; a premixing burner surrounding the pilot burner; and a pilot burner integral with the premixing burner.

[0012] In this way, the structure of the burner assembly is significantly simplified. The number of component parts of the burner assembly is in fact reduced and the pilot burner has a reduced axial length with respect to the prior art solutions, since the burner assembly can be fixed only to the combustion chamber wall and the pilot burner and the premixing burner no longer need to be coupled to other fixed structures of the gas turbine station or the combustion chamber (such as a pressure vessel) as normally made in the prior art solutions. Due to the reduced axial length of the pilot burner, the thermal expansion displacements of the pilot burner are advantageously reduced. In addition, the fact that the burner assembly can be fixed only primarily to the combustion chamber wall simplifies the assembly operations, with obvious advantages in terms of cost and time savings.

[0013] According to a preferred embodiment of the invention, the premixing burner and the pilot burner are a monolithic body.

[0014] In this way, assembly time and costs are significantly reduced.

[0015] According to a preferred embodiment of the present invention, the premix burner and the pilot burner are two separate pieces fixed together.

[0016] According to a preferred embodiment of the present invention, the pilot burner is fixed to the inner surface of the premixing burner.

[0017] According to a preferred embodiment of the invention, the premix burner comprises an inlet portion coupled to a fuel supply assembly and an injection portion which, in use, extends about a longitudinal axis and is coupled to the inlet portion.

[0018] According to a preferred embodiment of the present invention, the injection portion is provided with a first end and a second end; the second end has a second section diameter lower than the first section diameter of the first end; and the inlet portion is connected to the second end.

[0019] According to a preferred embodiment of the invention, the pilot burner is fixed to the inlet surface of the premixing burner.

[0020] According to a preferred embodiment of the invention, the pilot burner is fixed to the inlet section of the premixing burner along at least two axially displaced contact zones. In this way, the fixation between the pilot burner and the premixing burner is also stable and reliable.

[0021] According to a preferred embodiment of the present invention, the pilot burner and the premixing burner are fixed together so as to define a sliding interface between the pilot burner and the premixing burner. In this way, relative axial displacement between the pilot burner and the premixing burner due to thermal expansion is allowed.

[0022] According to a preferred embodiment of the invention, the sliding interface is defined by an air gap between the pilot burner and the inlet section of the premixing burner.

[0023] According to a preferred embodiment of the present invention, the pilot burner comprises at least two concentric ducts; at least one of the ducts is provided with an extendable portion.

[0024] In this way, relative axial displacements in the pilot burner due to thermal expansion are compensated.

[0025] According to a preferred embodiment of the invention, the premix burner comprises at least one fuel supply duct which is provided with a further extendable portion. In this way, relative axial displacements due to thermal expansion are compensated in the premix burner.

[0026] Another object of the present invention is to provide a combustion chamber for a gas turbine power station which has a simplified structure.

[0027] According to the invention, there is provided a combustion chamber for a gas turbine according to claim 12 . BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention will now be described with respect to the accompanying drawings which illustrate some non-limiting embodiments, in which: Figure 1 is a schematic cross-sectional view of a burner assembly according to the present invention, with portions removed for clarity; Figure 2 is a schematic cross-sectional view of a burner assembly according to a second embodiment of the present invention, with parts removed for clarity. DETAILED DESCRIPTION

[0029] exist Figure 1 Reference numeral 1 in the drawing indicates a burner assembly (only partially shown here) for a combustion chamber 9 of a gas turbine power station.

[0030] The burner assembly 1 comprises a pilot burner 2 extending along a longitudinal axis A and a premixing burner 3 extending around the pilot burner 2 .

[0031] The pilot burner 2 and the premix burner 3 are coupled to a fuel supply assembly 4 (schematically represented in the drawings), which is connected to respective fuel supply circuits (not shown). In the non-limiting disclosure and illustrations herein, the fuel supply assembly 4 is arranged along the longitudinal axis A. However, variations of the fuel supply assembly 4 may be provided to facilitate the supply of fuel from other sides of the burner assembly 1. For example, the fuel supply assembly 4 may include a metal rigid hose (hose, sometimes also referred to as a hose or a snake) or / and a flexible hose, which is connected to the pilot burner 2 and the premix burner 3.

[0032] The pilot burner 2 comprises a lance 5 provided with a first duct 6 supplied in use with a first fuel, a second duct 7 supplied in use with air and a third duct 8 supplied in use with a second fuel.

[0033] Preferably, the first fuel is gas and the second fuel is fuel oil.

[0034] Preferably, the first duct 6 , the second duct 7 and the third duct 8 are concentric and extend around the longitudinal axis A.

[0035] In the non-limiting example disclosed here, the third duct 8 extends along the longitudinal axis A, the first duct 6 extends around the third duct 8 and the second duct 7 extends around the first duct 6 .

[0036] The first conduit 6 and the third conduit 8 are respectively supplied with the first fuel and the second fuel by the fuel supply assembly 4. Figure 1 and 2 The gas is supplied toward the inside of the combustion chamber 9 (indicated by the arrow in the figure).

[0037] The second conduit 7 has an axial length that is lower than the axial lengths of the first conduit 6 and the third conduit 8 .

[0038] The lance 5 has an end tip 10 which faces toward the inside of the combustion chamber 9 .

[0039] The spray gun 5 is schematically represented in the drawings. Preferably, the spray gun 5 is provided with a plurality of first nozzles (not shown) connected to the first conduit 6 and with a plurality of second nozzles (not shown) connected to the second conduit 7 and a plurality of third nozzles (not shown) connected to the third conduit 8.

[0040] The lance end tip 10 preferably has a rounded section and is provided with a rounded edge 15. The end tip 10 comprises an end surface 16 which is defined by a respective end wall 17 and which is preferably flat.

[0041] The premix burner 3 extends around the pilot burner 2 and mainly comprises an inlet portion 20 coupled to the supply assembly 4 and an injection portion 21 coupled to the inlet portion 20 , and an outlet portion 22 coupled to the injection portion 21 and the combustion chamber 9 .

[0042] The inlet portion 20 comprises a fuel supply duct 23 which is preferably annular and extends around the respective inlet portion of the pilot burner 2 .

[0043] The fuel supply duct 23 is dimensioned so as to allow simple insertion of the pilot burner 2 into the substantially cylindrical seat defined by the fuel supply duct 23 .

[0044] The fuel supply conduit 23 is supplied with fuel from the fuel supply assembly 4, and the fuel is supplied along the flow direction D (in Figure 1 and 2 The fuel supply conduit 23 is directed toward the inside of the combustion chamber 9. The fuel supplied to the fuel supply conduit 23 is gas.

[0045] In the fuel supply conduit 23, a plurality of air inlet channels 24 (indicated by dashed lines) are arranged, which are configured to supply air to the second conduit 7 of the pilot burner 2. The air supplied through the air inlet channels 24 is the air collected in a plenum 25 (only partly visible in the figure) communicating with the outlet of the compressor of the station, The injection portion 21 is preferably defined by a swirler 26 of frustoconical type, provided with air slots 27 (the air slots are not well visible in the drawing—the dashed arrows show the air flowing through them) and a fuel nozzle 28 .

[0046] The air tank 27 is supplied with air collected in a plenum 25 communicating with the outlet of the compressor of the station.

[0047] The fuel nozzles 28 are supplied with fuel from the fuel supply conduit 23 .

[0048] The injection portion 23 is provided with a first end portion 29 a and a second end portion 29 b ; the second end portion 29 b has a segment diameter lower than that of the first end portion 29 a .

[0049] The inlet portion 20 is coupled to the second end portion 29b, and the outlet portion 22 is coupled to the first end portion 29a.

[0050] Preferably, the injection portion 21 is made of two shells assembled together.

[0051] The outlet portion 22 preferably has a cylindrical shape and is generally defined as a CBO (cylindrical burner outlet). The outlet portion 22 is coupled to a wall 31 of the combustion chamber 9 .

[0052] The pilot burner 2 and the premix burner 3 are integrated.

[0053] In other words, the pilot burner 2 and the premixing burner 3 are rigidly fixed together.

[0054] Preferably, the pilot burner 2 is fixed to at least a part of the inner surface of the premixing burner 3. The inner surface of the premixing burner 3 is the surface of the premixing burner 3 that faces the pilot burner 2 in use.

[0055] In the non-limiting example disclosed and illustrated herein, the premix burner 3 and the pilot burner 2 are two separate pieces fixed together. Preferably, the premix burner 3 and the pilot burner 2 are fixed directly together.

[0056] According to an embodiment not shown, the premixing burner 3 and the pilot burner 2 can be manufactured as a single block. For example, the single block can be obtained by additive manufacturing or by a casting process.

[0057] In detail, the pilot burner 2 is fixed to the inlet portion 20 of the premixing burner 3. Specifically, the outer surface of the pilot burner 2 is fixed to the inner surface of the inlet portion 20 of the premixing burner 3.

[0058] exist Figure 1 In the non-limiting example illustrated in , the outer surface of the second conduit 7 is fixed to the inner surface of the inlet portion 20 .

[0059] Preferably, the outer surface of the second conduit 7 is fixed to the inner surface of the inlet portion 20 at the boundary with the injection portion 21 .

[0060] Preferably, the fixing of the pilot burner 2 is carried out along at least one contact zone 30 (schematically indicated as a black dot in the drawing) of the inner surface of the inlet section 20 .

[0061] The fixing of the pilot burner 2 to the inner surface of the inlet section 20 may be achieved, for example, by welding, by bolts or by clamping means, by casting or by additive manufacturing.

[0062] According to Figure 2In the variant illustrated in FIG. 2 , the pilot burner 2 and the premixing burner 3 are fixed together so as to define a sliding interface 35 between the pilot burner 2 and the inlet portion 20 of the premixing burner 3 .

[0063] The sliding interface 35 allows relative axial movement between the pilot burner 2 and the premix burner 3 due to thermal expansion.

[0064] In the non-limiting example disclosed and illustrated herein, the sliding interface 35 is defined by an air gap 36 between the pilot burner 2 and the inlet portion 20 of the premix burner 3 .

[0065] Preferably, the sliding interface 35 is defined by an air gap 36 between the outer surface of the second duct 7 and the inner surface of the inlet portion 20 of the premix burner 3 .

[0066] The air gap 36 is preferably arranged along the inlet portion 20 near the injection portion 21 .

[0067] The outer surface of the pilot burner 2 is fixed to the inner surface of the inlet portion 20 of the premixing burner 3 .

[0068] exist Figure 2 In the non-limiting example illustrated in , the outer surface of the first conduit 6 is fixed to the inner surface of the inlet portion 20 .

[0069] Preferably, the inner surface of the inlet portion 20 is fixed to the outer surface of the first duct 6 near the start of the second duct 7 .

[0070] Similar to Figure 1 In the exemplary embodiment, the fixing of the pilot burner 2 is realized along at least one contact zone 30 (schematically indicated by a black dot in the drawing) of the inner surface of the inlet section 20 .

[0071] The fixing of the pilot burner 2 to the inner surface of the inlet section 20 may be achieved, for example, by welding, by bolts or by clamping means, by casting or by additive manufacturing.

[0072] According to a variant, not shown, the fixing of the pilot burner 2 to the premixing burner 3 can be carried out along at least two contact zones that are axially displaced in order to ensure a more stable connection. Figure 1 and Figure 2 The connections are connected by a combination of the connections shown in the figure.

[0073] about Figure 1 and Figure 2 In the two embodiments, the first duct 6 , the second duct 7 and the third duct 8 of the pilot burner 2 and the fuel supply duct 23 of the premix burner 3 are provided with at least one extendable portion 37 .

[0074] These extendable portions 37 may be provided in order to compensate for axial displacements due to thermal expansion of the first 6 , second 7 and third 8 ducts of the pilot burner 2 and the fuel supply duct 23 of the premix burner 3 .

[0075] exist Figure 2 In the embodiment shown in , in which a sliding interface 35 is provided between the pilot burner 2 and the inlet portion 20 of the premixing burner 3 , the second duct 7 does not require an extendable portion, since thermal expansion is compensated by sliding between the pilot burner 2 and the inlet portion 20 of the premixing burner 3 .

[0076] In the non-limiting example disclosed and illustrated herein, the extendable portion 37 is defined by a corrugated portion of the conduit.

[0077] According to a variant not shown, the extendable portion may be defined by a helical wrapped portion of the catheter.

[0078] Finally, it is evident that modifications and variations may be effected to the burner assembly and the combustion chamber described herein, without departing from the scope of the present invention as defined in the appended claims.

Claims

1. A burner assembly for a combustion chamber (9), comprising: a pilot burner (2) extending along a longitudinal axis (A), said pilot burner (2) comprising a lance (5) provided with a first duct (6) supplied in use with a first fuel, a second duct (7) supplied in use with air and a third duct (8) supplied in use with a second fuel; a premix burner (3) surrounding the pilot burner (2) and comprising an inlet portion (20) coupled to a fuel supply assembly (4) and an injection portion (21), the injection portion extending in use around the longitudinal axis (A) and coupled to the inlet portion (20); the injection portion (21) being defined by a swirl nozzle (26) of frustoconical type provided with air slots (27) and fuel nozzles (28); The burner assembly is characterized in that the pilot burner (2) is integral with the premixing burner (3) and is fixed to the inner surface of the inlet portion (20) of the premixing burner (3) so as to define a sliding interface (35) between the pilot burner (2) and the premixing burner (3); the sliding interface (35) is defined by an air gap (36) between the pilot burner (2) and the inlet portion (20) of the premixing burner (3) to allow relative axial displacement caused by thermal expansion between the pilot burner (2) and the premixing burner (3).

2. The burner assembly according to claim 1, wherein: The first duct (6), the second duct (7) and the third duct (8) are concentric; the second duct (7) has an axial length that is lower than the axial lengths of the first duct (6) and the third duct (8); the premixing burner (3) and the pilot burner (2) are a single block, and the sliding interface (35) is defined by an air gap (36) between the outer surface of the second duct (7) and the inner surface of the inlet portion (20) of the premixing burner (3).

3. The burner assembly according to claim 1, wherein: The premix burner (3) and the pilot burner (2) are two separate pieces fixed together.

4. A burner assembly according to any one of the preceding claims, wherein: The injection portion (21) is provided with a first end (29a) and a second end (29b); the second end (29b) has a second section diameter lower than the first section diameter of the first end (29a); the inlet portion (20) is connected to the second end (29b).

5. The burner assembly according to claim 4, wherein: The pilot burner (2) is fixed to the inlet portion (20) of the premixing burner (3) along at least two axially displaced contact zones.

6. A burner assembly according to any one of the preceding claims, wherein: The pilot burner (2) comprises at least two concentric ducts (7; 8; 9); at least one of the ducts (7; 8; 9) is provided with an extendable portion (37).

7. A burner assembly according to any one of the preceding claims, wherein: The premix burner (3) comprises at least one fuel supply duct (23) provided with a further extendable portion (37).

8. A combustion chamber for a gas turbine power station comprising a burner assembly (1) as claimed in any one of the preceding claims.

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