WO2014114533A1

WO2014114533A1 - Burner system having turbulence elements

Info

Publication number: WO2014114533A1
Application number: PCT/EP2014/050651
Authority: WO
Inventors: Andreas Böttcher; Boris Ferdinand Kock; Bernd Prade; William R. Ryan; Richard L. THACKWAY; Daniel Vogtmann; Ulrich Wörz; Berthold Köstlin; Lars TERJUNG
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG; Siemens Corp
Priority date: 2013-01-24
Filing date: 2014-01-15
Publication date: 2014-07-31
Anticipated expiration: 2015-07-24
Also published as: EP2948715B1; EP2948715A1

Abstract

Burner system having turbulence elements The invention relates to a burner system (2, 3), especially for use in a gas turbine, having an annular channel (6, 13) for the supply of combustion air, wherein the annular channel (6, 13) has an axis of symmetry (12), a fuel duct (4, 5, 19, 20, 21) for the supply of fuel, a plurality of turbulence elements (29) for generating highly turbulent combustion air and an inlet for fuel (10, 11, 15, 16, 17) from the fuel duct (4, 5, 19, 20, 21) into the annular channel (6, 13) down- stream of the turbulence elements (29), wherein carrier elements (30) of the turbulence elements (29) extend in the radial direction and at least one wing (31) is arranged on each of the carrier elements (30), wherein the projection of a wing (31), which is arranged radially toward the outside with respect to the axis of symmetry (12), onto a cross-sectional area of the annular channel (6, 13) is greater than the projection of a wing (31) which is arranged radially toward the inside with respect to the axis of symmetry (12).

Description

Burner system having turbulence elements

The invention relates to a burner system, especially for use in a gas turbine installation.

The mixing of fuel and air is of central importance to the combustion process. NO_x and CO emissions, the thermoacoustic properties of the flame and also the shape and position of the flame are determined decisively by the quality of the mixing. In particular, a fuel/air mixture which is as homogeneous as possible leads in this context to low NO_x emissions. What is more, however, the mixing also influences the

thermoacoustic behavior of the burner. Acoustic excitations which are caused by the combustion process thus arise in the combustion chamber. These excitations are either damped or amplified, depending on their amplitude and frequency and al^¬ so on the natural frequency of the combustion chamber struc^¬ ture. If the frequencies of the thermoacoustic oscillations coincide with the natural frequencies of the structure and are in phase therewith, large-amplitude mechanical oscilla^¬ tions arise, which can have a critical effect on the life of the components.

In the case of premix burner systems, for example also in pi^¬ lot burner systems, the fuel is mixed into the surrounding airflow through small bores in the vanes of the swirler in order to improve the mixing of fuel and air.

EP 1 400 752 Bl discloses a perforated plate for producing a controlled pressure drop across the burner and for guiding the flow, this perforated plate being arranged at the inlet to the swirler (vane row) of the burner. This pressure drop is necessary in order to be able to bring about the cooling of the turbine blades in a controlled manner. This perforated plate is, however, not optimal in terms of fluid dynamics and does not necessarily produce an even flow onto the swirl vanes.

EP 0 956 475 Bl discloses a burner in which additional turbu^¬ lence is generated by means of a multiplicity of flat and ap^¬ proximately equal-sized deflection elements.

The object of the invention is to provide a burner system, of the type mentioned in the introduction, which allows improved mixing of fuel and air and, simultaneously, is as simple and as cheap as possible to manufacture and to install.

The invention achieves this object in that it provides that, in the case of such a burner system, especially for use in a gas turbine, having an annular channel for the supply of com^¬ bustion air, wherein the annular channel is formed by a hub and an outer casing and has an axis of symmetry, a fuel duct for the supply of fuel, a plurality of turbulence elements for generating highly turbulent combustion air and an inlet for fuel from the fuel duct into the annular channel down^¬ stream of the turbulence elements, wherein carrier elements of the turbulence elements extend in the radial direction from the hub to the outer casing and at least one wing is ar^¬ ranged on each of the carrier elements, the projection of a wing, which is arranged radially toward the outside with re^¬ spect to the axis of symmetry, onto a cross-sectional area of the annular channel is greater than the projection of a wing which is arranged radially toward the inside with respect to the axis of symmetry. Targeted arrangement of the wings (for example in a radially irregular manner) can force the production of local differences in mixing. These differences in mixing influence the acoustics and, where appropriate, can mitigate or suppress critical combustion modes. Radial differences in the effec^¬ tive cross section of the wings with respect to a flow of air in the annular channel give rise to a suitable area ratio be^¬ tween the mixer elements and the annular channel, and thus also improved and/or adjustable mixing of fuel and air with regard to combustion stability and lower emissions.

In order to generate more turbulence instead of swirl, it is expedient if each carrier element has at least two wings and, in particular, if the carrier elements have pairs of wings, in which the wings are arranged in an inclined manner in mu- tual opposition with respect to the cross-sectional area of the annular channel, such that in each case opposite local^¬ ized swirl can be imparted to air flowing past said wings, resulting overall in increased turbulence.

In an expedient manner, the turbulence elements are arranged at an inlet into the annular channel.

In an advantageous embodiment of the invention, the angle of attack of the wings varies over the circumference of the an^¬ nular channel or in the radial direction. A different effec^¬ tive cross section can be achieved for the same size of wing by means of the irregular radial gradation, but also by means of a gradation on the circumference.

In an alternative advantageous embodiment, wings which are arranged radially further toward the outside have larger sur^¬ faces than wings which are arranged radially further toward the inside. Thus, even when the wings are at the same angle of attack, the area ratio of the mixer elements is adapted to the vane passage.

In a preferred configuration, the wings taper away from the carrier elements and, in particular, are trapezoidal or tri- angular in shape. This configuration achieves particularly intense turbulence.

It is further preferred that the turbulence elements are con^¬ nected to one another on the hub side via an annulus . The an- nulus can be separated as required, so as to enable simple assembly and disassembly.

The burner is preferably configured in such a way that swirl vanes are arranged in the annular channel downstream of the turbulence elements. As a result, a turbulence element having the positive effects on the homogeneity of the mixing of fuel and combustion air is used in combination with swirl vanes, which have a positive effect on the stability of combustion.

Preferably, at least one of the swirl vanes is formed as a hollow vane, out of which fuel can be introduced into the an^¬ nular channel. This configuration makes it possible to use an even injection of fuel from a swirl vane which is formed as a hollow vane, the effect of which is to further homogenize the fuel/air mixture in combination with the abovementioned ad^¬ vantages .

In a preferred configuration, the burner is formed as a pilot burner by means of which a pilot flame can be generated in order to maintain the combustion, wherein the wings are arranged on the carrier elements substantially from the inside to the middle, as seen in the radial direction. Particularly in the case of the pilot burner, the cross section of the an- nular channel is comparatively small, so that a comparatively deep fuel spray penetration is present in the pilot burner. It is therefore important, in particular radially toward the inside, that increased turbulence causes improved mixing of fuel and combustion air also in this region.

In another preferred configuration, the burner is formed as a main burner. The relative depth of penetration of the fuel into the air flow is less that in the case of the pilot burn^¬ er, for which reason increased turbulence is used also radi- ally toward the outside in order to achieve improved mixing. For this reason, the wings are arranged in a manner distrib^¬ uted on the carrier elements over the entire radial extent of the carrier elements.

Finally, an advantageous burner includes both a pilot burner system and a main burner system in accordance with the invention .

The invention will be explained in more detail by way of ex^¬ ample with reference to the drawings, in which, schematically and not to scale: Figure 1 shows a burner having a main burner system and a pilot burner system in a highly schematized basic diagram;

Figure 2 shows a side view of a main burner system having a perforated plate in accordance with the prior art;

Figure 3 shows a static mixer having turbulence elements in accordance with the invention;

Figure 4 shows a view in the direction of the axis of sym^¬ metry of a burner system in accordance with the invention; Figure 5 shows a view in the radial direction of the burn^¬ er system; and

Figure 6 shows a pilot burner system in accordance with the invention. Figure 1 shows, schematically and by way of example, the burner 1 in accordance with the invention in a highly schematized basic diagram with reference to which the concept un^¬ derlying the burner 1 is described.

The burner 1 in accordance with the invention which can be used for example in the combustion chamber of a gas turbine plant, where appropriate in combination with several burners of the same type, comprises an inner pilot burner system 2 and a main burner system 3 which surrounds the pilot burner system 2 concentrically. Both the pilot burner system 2 and the main burner system 3 can optionally be operated with gas^¬ eous and/or liquid fuels such as natural gas or fuel oil.

The pilot burner system 2 comprises, as fuel channels, an in^¬ ner oil supply channel 4 and, concentrically surrounding this, an inner annular gas supply channel 5. This is, in turn, concentrically surrounded by an inner annular channel 6 for the supply of combustion air. In addition, a suitable ignition system (not shown in the figure) can be arranged in or on this annular channel 6. The pilot burner system 2 has an outlet opening 8 which faces a combustion chamber 7 and in the region of which swirl vanes 9 are arranged in the annular channel 6. The pilot burner system has two inlets for fuel: by means of nozzle openings 10, gas can be injected into the annular channel 6 from the inner gas supply channel 5 in the region of the swirl vanes 9 or upstream of the swirl vanes 9 (injection of the gas from the inner gas supply channel 5 can alternatively or in addition occur also by means of nozzles in the swirl vanes 9) . Oil from the oil supply channel 4 can be injected into the supplied air and/or supplied inert sub^¬ stance downstream of the swirl vanes 9 by means of the oil nozzle 11. The purpose of the pilot burner system 2 is to maintain sta^¬ ble combustion operation in the burner 1, since the latter is usually operated with a lean mixture which tends toward in^¬ stabilities. The pilot burner system 2 can, in a manner known per se, be operated as a diffusion burner with oil and/or gas, whereby the fuel is injected directly into the flame.

However, it is also possible to operate the pilot burner sys^¬ tem 2 as a premix burner, whereby the fuel is thoroughly mixed with air before the mixture is supplied to the flame.

The main burner system 3 which surrounds the pilot burner system 2 comprises an annular channel 13 for the combustion air, which channel is radially toward the outside with re^¬ spect to the axis of symmetry 12 of the burner systems 2, 3, and through which channel there extend a plurality of swirl vanes 14 of a swirl vane blading. These swirl vanes 14 have first gas nozzles 15 as fuel inlets and, where appropriate, as shown in figure 1, second gas nozzles 16, through which fuel gas can be injected into the air flowing in through the radially outer annular channel 13. Oil can additionally be injected into the air flowing through the annular channel 13 by means of oil nozzles 17 as a further inlet for fuel. Alt^¬ hough the present exemplary embodiment relates to oil and oil nozzles, this is intended to be merely representative of suitable liquid fuels and corresponding nozzles.

The first gas nozzles 15 and second gas nozzles 16 which are located in the swirl vanes 14, and the oil nozzles 17, are supplied with fuel via a fuel supply arrangement, located ra- dially toward the inside, having fuel channels, what is re^¬ ferred to as the hub 18. First and second annular gas distri^¬ bution channels 19 and 20, which supply the gas nozzles 15 and 16 with gas, are arranged in this hub. Moreover, an annu- lar oil distribution channel 21, which supplies the oil nozzles 17 with oil, is arranged in the hub 18. The fuel chan^¬ nels, that is to say the gas distribution channels 19, 20 and the oil distribution channel 21, are supplied with the appro^¬ priate fuel via gas supply channels 22, 23 and via an oil supply channel 24, respectively. The oil supply channel 24 has a dedicated oil supply pipe 25.

Figure 2 shows a perspective side view of a known main burner system 3 before installation into the combustion chamber. A perforated plate 26 having evenly spaced holes is arranged at the inlet of the annular channel 13 for combustion air of the main burner system 3 for the purpose of generating a controlled pressure drop over the main burner system 3 and for guiding the flow, the perforated plate 26 being only partial^¬ ly shown in figure 2. A perforated plate of this type is usu- ally not provided in the pilot burner system 2, even though this is in principle conceivable.

Figure 3 shows the static mixer 27 of a main burner system 3 in accordance with the invention. The static mixer 27 encompasses an annulus 28, on which turbulence elements 29 are ar- ranged. The turbulence elements 29 consist in each case of one carrier element 30, on which individual or multiple wings 31 are arranged. In the preferred embodiment of figure 3, the wings 31 are arranged in pairs, in an inclined manner on the carrier elements 30 in mutual opposition with respect to the cross-sectional area of the annular channel 13. Fundamental^¬ ly, the number of turbulence elements 29, the number of wings 31 per mixing element 29 or carrier element 30 and the shape and angle of attack of the wings 31 are determined by the mixing profile to be achieved and also by the pressure drop to be produced.

The static mixer 27 is arranged at the inlet to the annular channel 13 for the supply of combustion air, and imparts strong turbulence to the inflowing air, resulting in better mixing of air and fuel in the subsequent vane injection re^¬ gion .

In order to keep the area ratio of the static mixer 27 to the annular channel 6, 13 constant in the radial direction, the size of the wings 31 can vary in the radial direction and can be adapted to the respective geometry of the annular channel 6, 13. As can be seen particularly clearly in figure 4, in a view parallel to the axis of symmetry 12 into the annular channel 13 of the main burner system 3, the annular channel 13 increases in size in the radially outward direction. The surface area of the respective wings 31 increases in a corre^¬ sponding manner, the further out they are arranged on the carrier element 30. The wings 31 in figure 4 are trapezoidal in shape.

Figure 5 shows adjacent carrier elements 30 as seen in the radial direction. The direction of flow of the combustion air 32 is illustrated by means of arrows. The wings 31 of one carrier element 30 extend into the free space between the wings 31 of an adjacent carrier element 30.

Figure 6 shows a pilot burner system 2 in accordance with the invention. The turbulence elements 29 are arranged in an off^¬ set manner with respect to the swirl vanes 9. No turbulence element 29 is provided at the point where the ignition device 33 is located. The annulus 28, by means of which the carrier elements 30 of the turbulence elements 29 are connected to one another, can be separated as required during installa^¬ tion. Figure 6 also shows that the wings 31 are arranged dif^¬ ferently on the carrier elements, depending on their radial position.

Claims

Patent claims

1. A burner system (2, 3), especially for use in a gas turbine, having an annular channel (6, 13) for the supply of combustion air, wherein the annular channel (6, 13) has an axis of symmetry (12), a fuel duct (4, 5, 19, 20, 21) for the supply of fuel, a plurality of turbulence elements (29) for generating highly turbulent combustion air and an inlet for fuel (10, 11, 15, 16, 17) from the fuel duct (4, 5, 19, 20, 21) into the annular channel (6, 13) downstream of the turbulence elements (29), wherein carrier elements (30) of the turbulence elements (29) extend in the radial direction and at least one wing (31) is arranged on each of the carri^¬ er elements (30), characterized in that the projection of a wing (31), which is arranged radially toward the outside with respect to the axis of symmetry (12), onto a cross- sectional area of the annular channel (6, 13) is greater than the projection of a wing (31) which is arranged radial^¬ ly toward the inside with respect to the axis of symmetry (12) .

2. The burner system (2, 3) as claimed in claim 1, wherein each carrier element (30) has at least two wings (31) .

3. The burner system (2, 3) as claimed in either of claims 1 and 2, wherein each carrier element (30) has pairs of wings, in which the wings (31) are arranged in an inclined manner in mutual opposition with respect to the cross- sectional area of the annular channel (6, 13) .

4. The burner system (2, 3) as claimed in one of the pre^¬ ceding claims, wherein the turbulence elements (29) are ar^¬ ranged at an inlet into the annular channel (6, 13) .

5. The burner system (2, 3) as claimed in one of the pre^¬ ceding claims, wherein the angle of attack of the wings (31) varies over the circumference of the annular channel (6, 13) or in the radial direction.

6. The burner system (2, 3) as claimed in one of the pre^¬ ceding claims, wherein wings (31) which are arranged radial^¬ ly further toward the outside have larger surfaces than wings (31) which are arranged radially further toward the inside .

7. The burner system (2, 3) as claimed in one of the pre^¬ ceding claims, wherein the wings (31) taper away from the carrier elements (30) and, in particular, are trapezoidal or triangular in shape.

8. The burner system (2, 3) as claimed in one of the pre^¬ ceding claims, wherein the turbulence elements (29) are con- nected to one another on the hub side via an annulus (28) .

9. The burner system (2, 3) as claimed in one of the pre^¬ ceding claims, wherein swirl vanes (9, 14) are arranged in the annular channel (6, 13) downstream of the turbulence el- ements (29).

10. The burner system (2, 3) as claimed in claim 9, wherein at least one of the swirl vanes (9, 14) is formed as a hol^¬ low vane, out of which fuel can be introduced into the annu- lar channel (6, 13) .

11. The burner system (2) as claimed in one of the preceding claims, which is formed as a pilot burner system (2) and by means of which a pilot flame can be generated in order to maintain the combustion, wherein the wings (31) are arranged on the carrier elements (30) substantially from the inside to the middle, as seen in the radial direction.

12. The burner system (3) as claimed in one of claims 1 to 10, which is formed as a main burner system (3), wherein the wings (31) are arranged in a manner distributed on the car^¬ rier elements (30) over the entire radial extent of the car^¬ rier elements (30) .

13. A burner (1) having at least one burner system (2, 3) as claimed in one of the preceding claims.