EP2288852B1 - Method for operating a premix burner, and a premix burner for carrying out the method - Google Patents

Description

The invention relates to a method for operating a premix burner according to claim 1 and a premix burner for carrying out such a method according to claim 5.

Foreign ignited but then self-running combustion processes are often operated in gas turbines to reduce pollutant emissions via a main stream fuel system or a Hauptsindüsung with a lean outside the respective flame chamber generated gas-air mixture. The lean gas-air mixture, however, means that the respective combustion process has a correspondingly narrow stability range. The narrower the stability range, the more susceptible the combustion process to changing operating conditions, which can result in an unwanted extinction of the combustion process. To stabilize the combustion process, known premix burners have a pilot gas system, via which a pilot flame is built up from a non-premixed fuel in the flame chamber. In addition to stabilizing the combustion process, the pilot flame often also serves to ignite the respective combustion process, so that it is consequently positioned in the vicinity of an ignition orifice of the premix burner. Pollutant emissions are in the background compared to the stabilization of the combustion process.

A premix burner for gaseous fuels and a method for controlling this premix burner is in the DE 10 2005 054 442 A1 shown. This premix burner has a multi-stage main injection with a plurality of main nozzles for injecting a gas-air mixture into a flame chamber and a central pilot gas system. To ignite the gas-air mixture, a pilot flame of unmixed main fuel is formed via the pilot gas system. From start up to a predetermined load ratio only a certain number of main nozzles are turned on. If a predetermined load ratio is under or exceeded If more main nozzles are switched on or already operated main nozzles are closed.

Another premix burner for gas turbines and a method for operating such a premix burner is in the DE 103 34 228 A1 described. This premix burner for gaseous fuels has a main injection and a central multi-stage pilot gas system. The main injection has a nozzle group of main nozzles for injecting a premixed main fuel. The central multi-stage pilot gas system has a nozzle group of diffusion nozzles for injecting unmixed diffusion fuel and an independently controllable nozzle group of premix nozzles for additional injection of the premixed main fuel.

When the premix burner is ignited, the largest fuel fraction is introduced via the diffusion stages of the pilot gas system. As the load increases, the premix nozzles of the pilot gas system and main nozzles of the main injection are switched on. The diffusion nozzles are moved back. At full load, the premix nozzles and main nozzles are fully operational and the diffuser nozzles are reduced to a minimum of the total fuel mass flow.

A disadvantage of this method is that the stability range of the combustion process, despite the multi-stage pilot gas system is not significantly disseminated. Furthermore, a complex control of the fuel supply is necessary. Furthermore, the premix burner is sensitive to changing fuel compositions. A premix burner and a method having the features of the preamble of claims 1 and 4, respectively, is disclosed in U.S.P. WO 01/59369 A1 disclosed.

The object of the present invention is to provide a method for operating a premix burner for gaseous fuels, which is more stable to changing environmental conditions and can be easily adapted to changing fuel compositions and fuel qualities, and a premix burner for carrying out such a method.

This object is achieved by a method having the features of claim 1 and by a premix burner having the features of claim 4.

A method according to the invention provides, via a main injection, a gas-air mixture as main fuel via a. Spin swirl generator into a flame chamber. A diffusion fuel of a central pilot gas system is injected into the flame chamber in the form of at least two partial streams with different directions or orientations.

The injection of the diffusion fuel according to the invention as at least two partial streams with different orientations effects a similar effect as a premix. At the same time, a combustion process with the injection according to the invention shows a substantially improved stability as well as an increased flexibility compared to varying fuel compositions and fuel qualities.

According to the invention, the first partial flow is injected transversely or perpendicularly to the flow direction of a main fuel flow that forms in the flame chamber. The second partial flow is injected obliquely to the burner longitudinal axis. The first partial flow transverse to the flow direction of the Hauptbrennstoffstromss causes a similar effect as a premix. The second flow obliquely to the burner longitudinal axis shows less turbulence and a lower mixing than the first partial flow transversely to the flow direction, whereby the diffusion fuel fraction in the flow direction is less sensitive to changes and the respective combustion process is more stable.

Preferably, the gas-air mixture of the main injection is introduced radially into the flame chamber.

In one embodiment, the gas-air ratio of the main fuel is controlled via the air supply and not via the main fuel nozzles.

An inventive premix burner for gaseous fuels has a flame chamber, a Hauptsindüsung for injecting a gas-air mixture as Main fuel in the flame chamber, a swirl generator for swirling the main fuel and arranged in the burner bottom central pilot gas system for injecting a diffusion fuel. According to the invention, the pilot gas system has a multi-stage design with at least one axial diffusion nozzle for injecting a first partial flow of the diffusion fuel and one or more diffusion nozzles arranged obliquely to the longitudinal axis of the burner for feeding in a second partial flow of the diffusion fuel.

In one embodiment, the at least one employed diffusion nozzle is set in the direction of flow of the main fuel stream.

Preferably, a plurality of axial and annealed diffusion nozzles are provided. In this case, the axial diffusion nozzles are located radially on the outside and the employed diffusion nozzles are positioned radially in the interior of the burner bottom.

The axial and annealed diffusion nozzles may form two or more concentric circles, the common center being on the burner longitudinal axis.

The diffusion nozzles can have different geometries. For example, the diffusion nozzles are formed as bores, grooves or longitudinal slots.

The pilot gas system preferably has more axial diffusion nozzles than employed diffusion nozzles. In particular, twice as many axial diffusion nozzles as employed diffusion nozzles can be provided.

In one embodiment, the premix burner is formed as a can burner with an at least partially cylindrical flame tube which is spaced from the burner bottom via the swirl generator.

Other advantageous embodiments of the invention are the subject of further subclaims.

• Fig. 1 einen Längsschnitt durch einen erfindungsgemäßen Vormischbrenner im Brennerbodenbereich, und
• Fig. 2 eine Draufsicht auf den Brennerboden aus Figur 1.

In the following, a preferred embodiment of the invention is explained in more detail with reference to schematic representations. Show it

• Fig. 1 a longitudinal section through a premix burner according to the invention in the burner bottom region, and
• Fig. 2 a plan view of the burner bottom FIG. 1 ,

FIG. 1 shows a highly simplified partial longitudinal section through a premix burner 2 according to the invention for a gas turbine. The premix burner 2 is designed as a can burner with a cylindrical flame chamber 4 for gaseous or liquid fuel. It has a main injection 6 and a central multi-stage pilot gas system 8 according to the invention.

The flame chamber 4 is bounded on one side in the axial direction by a burner base 10 and radially by a flame tube 12. A remote from the burner base 10 end portion 14 of the flame tube 12 is widened in a funnel shape.

The main injection 6 is used to inject a gas-air mixture as a premixed main fuel 16. The injection takes place radially to the burner longitudinal axis 18 via unspecified main nozzles, which open into a radial swirl generator 20. Preferably, the main injection has 24 main nozzles.

The radial swirl generator 20 is arranged between the burner base 10 and the flame tube 12. It causes the main fuel 16 to be acted upon by a swirl pulse and swirled into the flame chamber 4 occurs. In the flame chamber 4, a main fuel flow whose direction is indicated by the respective arrows.

The pilot gas system 8 is used for injecting a non-premixed diffusion fuel and has a multiplicity of axial diffusion nozzles 22a, 22b and a multiplicity of diffusion nozzles 24a, 24b set obliquely to the burner longitudinal axis 18. The diffusion fuel is injected into the flame chamber 4 via the axial diffusion nozzles 22a, 22b and the employed diffusion nozzles 24a, 24b as two partial streams 26, 28.

The axial and employed diffusion nozzles 22a, 22b, 24a, 24b are arranged in the burner bottom 10, so that an injection of the partial streams 26, 28 takes place downstream of the entry of the main fuel stream 16. The axial diffusion nozzles 22a, 22b transverse or perpendicular to the flow direction of the main fuel 16 in the flame chamber 4 cause the first partial flow 26 to be intensively mixed with the main fuel 16. The employed diffusion nozzles 24a, 24b are oriented such that the second partial stream 28 is injected into the flame chamber 4 in the flow direction of the main turbulence fuel 16 and the mixing is thus minimized, which promotes the stability of the combustion process.

According to the front view of the burner bottom 10 in FIG FIG. 2 The axial diffusion nozzles 22a, 22b,... and the employed diffusion nozzles 24a, 24b,... form two concentric circles whose common center 30 lies on the burner longitudinal axis 18. In this case, the axial diffusion nozzles 22a, 22b,... Are located radially outward and the employed diffusion nozzles 24a, 24b,... Are positioned radially inward. The diffusion nozzles 22a, 22b,..., 24a, 24b,... Are uniformly distributed over the respective circle, wherein in the illustrated embodiment, 24 axial diffusion nozzles 22a, 22b,..., And 12 employed diffusion nozzles 24a, 24b,. are provided. Thus, there are twice as many axial diffusion nozzles 22a, 22b, ... we employed diffusion nozzles 24a, 24b, .... The number of axial diffusion nozzles 22a, 22b, ... here corresponds to the number of main nozzles.

The axial diffusion nozzles 22 and the employed diffusion nozzles 24 are formed in this embodiment as bores.

In a preferred method according to the invention for operating the premix burner 2, a swirled gas-air mixture of the main injection 6 is injected radially into the flame chamber 4 via the radial swirl generator 20. By means of the multi-stage pilot gas system 8, a diffusion fuel as a first partial flow 26 and a second partial flow 28 is injected into the flame chamber 4. The first partial stream 26 is injected via the axial diffusion nozzles 22a, 22b,... And the second partial stream 28 into the flame chamber 4 via the employed diffusion nozzles 24a, 24b,. An adjustment of the gas-air ratio of the main fuel 16 to the respective load state via a change in the air supply of the main fuel 16. An adaptation of the gas-air mixture on a known up or Zusteuerung the main nozzles is not provided.

It should be mentioned that it is also conceivable to divide the diffusion fuel into more than two partial flows 26, 28. Likewise, this application is not limited to two equal or two different part streams 26, 28 of the diffusion fuel stream.

It should also be mentioned that the geometry of the diffusion nozzles 22a, 22b,..., 24a, 24b,... Is not limited to bores, but that grooves or longitudinal slots are also conceivable. Likewise, the geometry of the axial or employed diffusion nozzles can vary with each other. Further, the arrangement of the diffusion nozzles 22a, 22b, ..., 24a, 24b, ... is not limited to a circular arrangement, but other arrangements such as star positioning are also conceivable. An uneven distribution of the diffusion nozzles is also possible.

Disclosed is a method of operating a premix burner for gaseous fuels with a multi-stage pilot gas system, the diffusion fuel is injected as at least two partial streams with different orientations in a flame chamber of the premix burner, and a premix burner for performing the method.

LIST OF REFERENCE NUMBERS

2

premix

4

flame chamber

6

Haupteindüsung

8th

Pilot gas system

10

Brenner ground

12

flame tube

14

end

16

main fuel

18

Brenner axis

20

swirl generator

22a, 22b,

axial diffusion nozzle

24a, 24b,

Employed diffusion nozzle

26

first partial flow of the diffusion fuel

28

second partial flow of the diffusion fuel

30

Focus

Claims (11)

1. A method for operating a premix burner (2) for gas turbines with the steps:

   • injecting a gas-air mixture as main fuel (16) via a swirl generator (20) into a flame chamber (4) that is arranged longitudinally with respect to a burner longitudinal axis (18),

   • central injecting of a first part flow (26) of a diffusion fuel into the flame chamber (4) which is outwardly delimited by a burner base (10) and

   • central injecting of a second part flow (28) of the diffusion burner into the flame chamber (4) that is outwardly delimited by the burner base (10),

   characterized
   in that the injecting of the first part flow (26) takes place via at least one diffusion nozzle (22a, 22b, ...) which are arranged axially and in the burner base (10) transversely to the main fuel flow forming in the flame chamber (4), and
   in that the injecting of the second part flow (28) takes place via at least one diffusion nozzle (24a, 24b, ...) that is set obliquely to the burner longitudinal axis (18) and arranged in the burner base.
2. The method according to Claim 1, wherein the main fuel (16) is injected radially.
3. The method according to Claim 1 or 2, wherein the gas-air ratio of the main burner (16) is regulated via the air supply.
4. A premix gas burner for gas turbines for currying out the method according to Claim 1 with a flame chamber (4), a main injection (6) for injecting a gas-air mixture as main fuel (16) into the flame chamber (4) via a swirl generator (20) for swirling the main fuel (16) and a central pilot gas system (8) formed in the burner base (10) for injecting a diffusion fuel, characterized in that in the burner base (10) at least one axial diffusion nozzle (22a, 22b, ...) for feeding in a first part flow (26) of the diffusion fuel transversely to the main fuel flow forming in the flame chamber (4) and at least one diffusion nozzle (24a, 24b, ...) set obliquely to the burner longitudinal axis (18) for injecting a second part flow (28) of the diffusion fuel are arranged.
5. The premix burner according to Claim 4, wherein the at least one set diffusion nozzle (22a, 22b, ...) is set in flow direction of the main fuel flow.
6. The premix burner according to Claim 5, wherein a plurality of axial diffusion nozzles (22a, 22b ...) located radially outside and a plurality of set diffusion nozzles (24a, 24b; ...) which are radially located inside are provided.
7. The premix burner according to Claim 5 or 6, wherein the axial diffusion nozzles (22a, 22b, ...) and the set diffusion nozzles (24a, 24b, ...) form at least two circles that are concentric to one another, the common centre point (30) of which is lies on the burner longitudinal axis (18).
8. The premix burner according to any one of the Claims 4 to 7, wherein the axial diffusion nozzles (22a, 22b, ...) have a geometry other than the set diffusion nozzles (24a, 24b, ...).
9. The premix burner according to Claim 8, wherein the axial diffusion nozzles (22a, 22b, ...) and the set diffusion nozzles (24a, 24b, ...) are bores.
10. The premix burner according to any one of the Claims 4 to 9, wherein the pilot gas system (8) comprises more axial diffusion nozzles (22a, 22b, ...) than set diffusion nozzles (24a, 24b, ...), in particular twice as many axial diffusion nozzles (22a, 22b, ...) as set diffusion nozzles (24a, 24b, ...).
11. The premix burner according to any one of the Claims 6 to 10, wherein the flame chamber (4) is radially delimited in the vicinity of the burner base (10) by the swirl generator (20) and a cylindrical flame tube (12).

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