HK1145866B - Combustor nozzle - Google Patents

Description

Burner nozzle

Technical Field

The present invention relates to a combustor that may be used in a gas turbine. More specifically, the present disclosure relates to a nozzle system that injects fuel into a combustor.

Background

Gas turbines play a vital role in many applications, such as aircraft propulsion, marine propulsion, power generation, and driving processes such as pumps and compressors. Generally, a gas turbine includes a compressor, a combustor, and a turbine. In operation, air is fed into the system where it is compressed by a compressor, and a portion of the air is further mixed with fuel. The compressed air and fuel mixture is then combusted, causing expansion to drive the turbine.

To reduce emissions, the burner is designed to premix fuel and air prior to ignition. Premixed fuel and air combust at a lower temperature than stoichiometric combustion, which occurs during conventional diffusion combustion. As a result, premixed combustion results in lower NO_XAnd (5) discharging.

A typical combustor includes a plurality of primary fuel nozzles surrounding a central secondary nozzle. Conventional secondary nozzles may include both passages for diffusion fuel and premix fuel within the same elongated tubular structure. Such nozzles typically contain complex structures of passages within a single tubular shell. The passages for generating the diffusion flame extend along the length of the nozzle. The premixed fuel is distributed upstream of the diffusion tip to mix the fuel with compressed air flowing through the combustor prior to reaching a flame zone, which is located downstream of the nozzle. As a result, the channels for premixed fuel are generally shorter than the channels for diffusion fuel.

In addition, the premixed fuel may mix with air upstream of the diffusion tip and, more importantly, radially outward from the secondary nozzle structure. In such secondary nozzles, premixed fuel is carried along only a portion of the nozzle length until it is delivered radially outward from the nozzle body to the premix injector tip. At the injector tip, premixed fuel is distributed into the air flow path. As the fuel and air continue to move downstream along the remainder of the secondary nozzle length, they mix downstream of the nozzle tip, enabling more efficient combustion within the flame zone.

However, the compressed air is hot, while the fuel is typically cooler. The temperature differential of the fluids flowing through the various passages in the secondary nozzle may cause the materials making up the nozzle to thermally expand to varying degrees. It is expected that it would be advantageous to simplify the construction of the secondary nozzle to reduce the high stresses on the nozzle structure due to internal complexity, extreme operating conditions, and differential thermal expansion.

Disclosure of Invention

The invention provides a secondary nozzle provided in a combustor for a gas turbine. The secondary nozzle includes a flange and an elongated nozzle body extending from the flange. At least one premix fuel injector is radially spaced from the nozzle body and extends axially from the flange substantially parallel to the nozzle body.

The secondary nozzle includes a fuel source, a flange, and a first nozzle tube extending axially from the flange. At least one second nozzle tube is spaced radially outwardly from the first nozzle tube and a proximal end of the second nozzle tube is secured to the flange. The second nozzle tube is fluidly connected to a fuel source. The second nozzle tube has a distal end axially spaced from its proximal end and has at least one aperture therein. A passage extends between the proximal end and the distal end of the second nozzle tube, and the passage is fluidly connected to a source of fuel and the at least one aperture.

Drawings

FIG. 1 is a cross-sectional view of an exemplary combustor for a gas turbine with a plurality of primary nozzles and a secondary nozzle.

FIG. 2 is a perspective view of an exemplary primary and secondary nozzle.

Fig. 3 is a front view of a plurality of primary nozzles and a secondary nozzle shown in fig. 1 and 2.

Fig. 4 is a perspective view of the secondary nozzle shown in fig. 1-3.

Fig. 5 is a partial perspective view of the secondary nozzle shown in fig. 1-4.

Fig. 6 is a cross-sectional view of the secondary nozzle shown in fig. 1-5.

FIG. 7 is a schematic view of a portion of the secondary nozzle shown in FIGS. 1-6.

FIG. 8 is a schematic illustration of primary operating conditions of an exemplary combustor.

FIG. 9 is a schematic illustration of lean-lean conditions of an exemplary combustor.

FIG. 10 is a diagrammatical illustration of second stage combustion conditions of the exemplary combustor.

FIG. 11 is a schematic illustration of a premix condition of an exemplary combustor.

Detailed Description

An exemplary combustor for a gas turbine is described herein in detail. The illustrated type of combustor is one of a plurality of combustors that are generally positioned after the compressor stage within the gas turbine.

Referring now to the drawings, and initially to FIG. 1, a combustor is generally designated 10 and is illustrated as a dual stage, dual mode combustor having a combustor flow sleeve 12, a backwall assembly 14 and a combustor wall 13. Radially inward from the combustor wall 13 are a plurality of primary fuel nozzles 16 and a secondary fuel nozzle 18. The nozzles 16, 18 are used to inject fuel into the combustor 10.

The inlet air for combustion (and also for cooling) is pressurized by a turbine compressor (not shown) and then directed into the combustor 10 through a combustor flow sleeve 12 and a transition duct (not shown). The air flowing into the combustor 10 is used for combustion and cooling the combustor 10. Air flows in direction "a" between combustor flow sleeve 12 and combustor wall 13. Generally, the illustrated airflow is referred to as reverse flow because the direction "A" is in an upstream direction relative to the normal airflow through the turbine and combustor.

The combustor 10 includes a primary combustion chamber 42 and a secondary combustion chamber 44 downstream of the primary combustion chamber 42. The venturi throat region 46 is located between the primary combustion chamber 42 and the secondary combustion chamber 44. As shown in fig. 2 and 3, each primary nozzle 16 is arranged around the secondary nozzle 18. In FIG. 1, the centerbody 38 is defined by a liner 40 in the center of the combustor 10.

Referring now to fig. 1-3, each primary nozzle 16 is mounted on the back wall assembly 14. The primary nozzles 16 protrude from the rear wall 14 and provide fuel to the primary combustion chamber 42. Fuel is dispensed to the primary nozzles 16 through a primary fuel source 20. The spark or flame for combustion ignition within the primary combustion chamber 42 is typically provided by a spark plug or cross-fire tube (not shown).

An air swirler may be provided in connection with the primary nozzle 16 to facilitate mixing of combustion air with fuel to provide a ignitable air-fuel mixture. As described above, combustion air is channeled from the compressor and flows in direction "A" between combustor flow sleeve 12 and combustor wall 13. Upon reaching the rear wall assembly 14, the compressed air flows radially inward into the primary combustion chamber 42 between the combustor wall 13 and the rear wall 14. Additionally, for cooling, the combustor wall 13 may be provided with slots or louvers (not shown) in the primary and secondary combustion chambers 42, 44. The slots or louvers may also provide dilution air into the combustor 10 to regulate the flame temperature within the primary or secondary combustion chambers 42, 44.

Referring now to fig. 1-4, the secondary nozzle 18 extends from the flange 22 through the back wall 14 into the combustor 10. The secondary nozzle 18 extends to a point upstream of the venturi throat region 46 to introduce fuel into the secondary combustion chamber 44. The flange 22 may provide a means (not shown) for mounting the secondary nozzle 18 on the back wall 14 of the combustor 10. The mounting means may be a mechanical coupling, such as bolts, for securing the flange 22 to the rear wall 14 and facilitating removal of the nozzle 18, for example, for repair or replacement. Other attachment means are also contemplated.

The fuel for the primary nozzles 16 is provided by a primary fuel source 20 and is directed through the back wall 14. Secondary transfer and premix fuel sources 24, 25 are supplied to the secondary nozzle 18 via flange 22. Although not shown here, the secondary nozzle 18 may also have a diffusion or pilot circuit to inject fuel into the combustor 10.

The secondary nozzle 18 includes a nozzle body 30 and at least one premix fuel injector 32. As shown in FIG. 1, the secondary nozzle 18 is located within a centerbody 38 and is surrounded by a liner 40. As best shown in FIG. 3, each premix fuel injector 32 is disposed on flange 22 generally about nozzle body 30. Each premix fuel injector 32 has a generally oblong or elongated cross-sectional shape when viewed from the top. As best shown in fig. 3, a first side or end 34 of the injector 32 is disposed proximate the nozzle body 30. A second side or end 36 of the injector 32 is disposed radially outward from the first end 34.

Premix fuel injectors 32 are shown directly aligned between primary nozzles 16 and nozzle body 30 such that the air flow passes through centerbody 38 and around nozzle body 30. In this configuration, the second end 36 of the premix fuel injectors 32 is disposed proximate to the primary nozzles 16. The airflow "a" entering the combustor 10 flows radially inward from outside the combustor wall 13. A portion of the air flows downstream into and through the primary combustion chamber 42. Another portion of the air (e.g., 5-20% of the total air flowing through the combustor) flows radially inward into the center body 38 through the primary nozzle 16 and the primary combustion chamber 42 before flowing downstream through the center body. The direction of this second portion of the airflow along the flange 22 and the rear wall 14 is indicated by the letter "B" in fig. 3. Although other configurations may be employed, a maximum amount of airflow into centerbody 38 is enabled when premix fuel injector 32 is aligned radially inward from primary nozzle 16 between primary nozzle 16 and secondary nozzle 18. Similarly, although premix fuel injectors 32 are illustrated as having an elongated cross-section, other shapes may be used, such as circular, rectangular, triangular, and the like.

Referring now to FIGS. 5-7 and with continued reference to FIGS. 1-4, the secondary nozzle 18 is shown to include a nozzle body 30 and a premix fuel injector 32. As described above, the secondary nozzle 18 is located within the centerbody 38 and is surrounded by the liner 40 (FIG. 1). The nozzle body 30 extends along a longitudinal axis of the center body 38. The nozzle body 30 has a generally elongate cylindrical outer sleeve portion 52 defining a cavity 31 therein. As shown, each transfer fuel passage 64 is located in an outer portion of cavity 31. Each transfer fuel passage 64 extends distally from flange 22 and is disposed at circumferentially spaced locations. Well-known variations without conversion may also be employed.

Transfer fuel passage 64 is fluidly connected to transfer manifold 51, which is fueled by transfer fuel source 24. The transfer fuel passage 64 includes a long tube 66 and at least one radial passage 68. The passage 68 faces radially outwardly from the tube 66 and is aligned with an aperture 71 in the wall of the nozzle body 30. The passage 68 injects fuel through the opening 71 to the outside of the sleeve 52 to mix with the air flowing along the wall 52. The second opening 70 is shown upstream of the opening 71, the second opening 70 providing an inlet for air into the portion of the cavity 31 that surrounds the central tube positioned within the nozzle body 30. referring now to FIGS. A portion of the air flowing through the opening 70 is directed into the cavity 31 to cool the nozzle body 30. Air within the cavity 31 is discharged from an opening 58 in the nozzle tip 54. The central tube supplies fuel to the nozzle tip 54 to support the flame within the secondary combustion chamber 44 (see fig. 1 and 9-11). Opening 70 is separate from the fuel provided by passage 68 and the additional fuel provided by injector 32. It is noted that additional openings may be provided to mix the fuel flow outside of the nozzle body 30 or to introduce air flow into the cavity 31 of the nozzle. Also, the fuel passage 64 may not be required, if desired.

An outer sleeve portion 52 of the nozzle body 30 extends from the flange 22 to a distal end 54. The distal end 54 of the nozzle body 30 has at least one aperture 58 to allow pressurized air to flow from within the passageway 31 around the central tube portion.

As described above, fuel is supplied to the secondary nozzle 18 via the transfer fuel source 24 and the premix fuel source 25. As best shown in fig. 6, a transfer fuel source 24 extends into flange 22 to supply fuel to a transfer manifold 51, which transfer manifold 51 is fluidly connected to a transfer fuel passage 64. The premix fuel source 25 extends into the flange 22 and is in fluid communication with a premix manifold cavity 50, the premix manifold cavity 50 being fluidly connected to the premix fuel injectors 32.

Premix fuel injectors 32 extend distally from flange 22 and have a length less than the length of nozzle body 30. The distal end 60 of the premix fuel injector 32 includes premix orifices 62 to distribute fuel into the area of the center body 38 outside of the nozzle body 30. The premixed fuel mixes with the air flow within the combustor basket 40. When the mixture reaches the secondary combustion chamber 44, the mixture is optimized for efficient combustion within the secondary combustion chamber 44 (see FIG. 1).

Unlike typical secondary nozzles, where diffusion fuel and premix fuel are discharged through a single structure extending from the flange, the use of separate premix fuel injectors 32 standing upright herein allows the nozzle body 30 to be simplified. The illustrated injector 32 allows for a smaller number of internal passages within the nozzle body 30 than typical nozzles. This simplification reduces stresses on the secondary nozzle 18 that may be caused by temperature differences within the nozzle structure 18, 32 due to temperature changes of the fuel and compressed air. In addition, the desired design is easy to maintain and allows a degree of modularity, which is not possible in conventional secondary nozzles.

In addition to the illustrated configuration, premix fuel injectors 32 may have a distribution ring fluidly connected to one or more sets of premix holes 62. Other dispensing terminal configurations may also be used in conjunction with the particular type of premix fuel injectors 32 shown.

Referring to FIG. 8, in a typical "primary" condition, a flame 72 is first formed in the primary combustion chamber 42 upstream of the secondary combustion chamber 44. Fuel for this initial flame is provided only through the primary nozzles 16. In fig. 9, the flame 72 is formed within the secondary combustion chamber 44, while the flame 72 within the primary combustion chamber 42 continues. To form the flame 72 within the secondary combustion chamber 44, a portion of the fuel is injected through the secondary nozzle 18, while a majority of the fuel is supplied through the primary nozzle 16. For example, 30% of the total emission fuel is injected through the secondary nozzle, and 70% of the fuel is supplied through the primary nozzle 16. This flame configuration is referred to as a "lean-lean" type of condition.

In FIG. 10, the entire fuel stream is introduced through the nozzle body 30 of the secondary nozzle 18, forming a stable flame within the secondary combustion chamber 44. The flame in the primary combustion chamber 42 is extinguished by shutting off the fuel flow to the primary nozzle 16. During this "second stage" combustion condition, fuel previously injected through primary nozzle 16 is diverted to secondary nozzle 18 through transfer fuel passage 64. The switch and premix fuel is injected upstream of the flame 72. The fuel and air flowing through the secondary nozzle 18 are considered relatively "rich" at this stage because 100% of the fuel flows through the secondary nozzle 18 with only a portion of the air intended for combustion.

Referring now to FIG. 11, once a stable flame is established within the secondary combustion chamber 44 and the flame within the primary combustion chamber 42 is extinguished, the flow of fuel to the primary nozzle 16 may be re-supplied and the flow of fuel to the secondary nozzle 18 may be reduced. Since the flame in the primary combustion chamber 42 has been extinguished, the primary nozzle 16 functions as a premixer. In this "premixed" mode of operation, the flame is maintained within the secondary combustion chamber 44 due to the venturi throat region 46. For example, 83% of the total emission fuel may be supplied through the primary nozzle 16, while the remaining 17% of the fuel is injected through the secondary nozzle 18. Other proportional relationships are also possible.

It will be apparent to those skilled in the art that various changes in the embodiments described herein are possible in light of the disclosure herein. Thus, the invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.

Claims (12)

1. A secondary nozzle for a gas turbine combustor, the secondary nozzle comprising:

a flange;

an elongated nozzle body extending from the flange; and

a plurality of premix fuel injectors radially spaced from the nozzle body, the plurality of premix fuel injectors extending substantially parallel to the nozzle body from the flange axially along a portion of a length of the nozzle body up to a portion of the length of the nozzle body.

2. The secondary nozzle of claim 1, wherein the nozzle body has a first length and the plurality of premix fuel injectors have a second length that is less than the first length.

3. The secondary nozzle as claimed in claim 1, wherein the secondary nozzle is disposed within a combustor having primary nozzles arranged in an annular array around the secondary nozzle, the plurality of premix fuel injectors being disposed between the primary nozzles and the nozzle body of the secondary nozzle.

4. The secondary nozzle of claim 3, wherein the plurality of premix fuel injectors and the primary nozzle are equal in number.

5. The secondary nozzle of claim 4, wherein each of the premix fuel injectors of the plurality of fuel injectors is disposed between the nozzle body of the secondary nozzle and an adjacent one of the primary nozzles.

6. A gas turbine combustor comprising:

a secondary nozzle having:

a flange;

a fuel source in fluid communication with the flange;

a first nozzle tube extending from the flange and in fluid communication with the fuel source through the flange; and

a plurality of injector tubes having a proximal end secured to the flange and a distal end spaced from the proximal end, the injector tubes extending axially along a portion of the length of the first nozzle tube, the plurality of injector tubes fluidly connected to the fuel source through the flange and the connection being separate from the connection between the fuel source and the first nozzle tube.

7. The gas turbine combustor of claim 6, wherein the secondary nozzle further comprises at least one third tube extending from the flange and positioned within the first nozzle tube, the at least one third tube fluidly connected to a fuel source for selectively providing fuel to the gas turbine combustor.

8. The gas turbine combustor of claim 6, wherein the secondary nozzles are surrounded by an annular array of primary nozzles.

9. The gas turbine combustor of claim 8, wherein the primary nozzles are radially aligned with the plurality of injector tubes such that each of the plurality of injector tubes is positioned between one of the primary nozzles and the centrally located first nozzle tube.

10. The gas turbine combustor of claim 9, wherein each of the plurality of injector tubes has a generally elongated cross-section.

11. The gas turbine combustor of claim 10, wherein a first end of the elongated cross-section of each of the plurality of injector tubes is positioned proximate to the first nozzle tube and a second end of the elongated cross-section of each of the plurality of injector tubes is positioned proximate to one of the primary nozzles.

12. The gas turbine combustor of claim 6, wherein the plurality of injector tubes comprises a plurality of injector tubes arranged in an annular array around the first nozzle tube.