EP1645802A2 - Premix Burner - Google Patents

Abstract

The premixing burner has a grating for combustible air flow, a fuel dosing means (17a,17b) for intake of fuel and air inlet slots. The dosing of fuel in the combustible air is done with the help of fuel dosing means whereby at least one dosing means (5) is arranged in the spin area of the fuel flange (3).

Description

Technical area

The invention relates to a burner according to the preamble of the first claim.

State of the art

Premix burners operated according to the concept of lean premix combustion have low pollutant emissions, but also a clearly limited stability and operating range. In addition to the flashback into the mixing zone of the burner and the lifting and extinguishing of the premix flame, thermoacoustic vibrations lead to these restrictions. The extension of the stability range takes place during the conventional operation of a premix burner with a pilot injection, which is used in particular in the lower load range. Even small amounts of e.g. However, 10% pilot gas can lead to significantly higher pollutant emissions, since the pilot flames operate in diffusion mode. In the upper load range, the pilot injection is switched off or reduced as far as possible to ensure low pollutant emissions.

In the case of the premix burner known from EP 0 321 809 A1, a so-called double-cone burner, this pilot burner is realized by injecting fuel in the center of the swirl body, here called a double cone. The gas flowing into the interior of the double-cone burner burns in a flame which is deeply stabilized in the interior of the burner.

From EP 0 704 657 A2 a further premix burner is known, in which the pilot burner is realized by fuel from an annular gas channel with outwardly inclined outlet holes in the outer Rückströmzone the combustion chamber after the burner outlet flows. The escaping gas burns in a stabilized by the jump in cross section at the burner outlet flame.

Both in the design of the external piloting according to EP 0 704 657 A2 and in internal piloting according to EP 0 321 809 B1, optimal injection of the fuel can not be ensured over the entire load range in order to achieve the lowest pollutant emissions.

From WO 01/96785 A1 a burner with stepped premix gas injection is known in which a fuel lance protrudes into the swirl body. The fuel supply can be controlled so that outlet openings in the fuel lance and outlet openings on the swirler can be fed independently with premixed gas. The outlet openings on the swirl body and on the lance can be arranged in such a way that no outlet openings are arranged on the swirl body arranged opposite the swirl body at the outlet openings arranged on the lance.

Presentation of the invention

The invention has for its object to ensure in a burner of the type mentioned, over the entire load range optimal injection of the fuel and to suppress thermoacoustic oscillations even more effective.

According to the invention this is achieved by the features of the first claim. The essence of the invention is to achieve a stepped injection of the fuel into the combustion air by arranging a fuel lance projecting into the swirl space, whereby a part of the fuel injection means in the combustion air inlet slots is replaced by fuel injection means on the fuel lance.

Among other things, the advantages of the invention can be seen in the fact that optimum injection of the fuel is ensured over the entire load range. Due to the stepped injection via the lance and the additional injection openings, the operating range of premix burners can be extended. The operation of these fuel staging premix burners covers at least the entire operating range of conventional pilot / premix burners.

In addition, an asymmetric injection of the fuel pulsations can be prevented even more effective. The asymmetry refers to opposite in the flow direction pairs of injection ports and the injection openings in the lance. The asymmetry can be done statically by no injection opening is arranged in the opposite region of a Eindüsungsöffnung. However, this can also be done by an individual control of the fuel supply to the symmetrically present fuel injection openings or by rotating the lance. Opposing Brennstoffindüsungsöffnungen are then supplied by the control of different amounts of fuel and thus achieved depending on the load point or start or Abfahrbedingungen a symmetrical or asymmetric fuel profile in the swirl chamber of the swirl generator.
Furthermore, a graded fuel injection allows an optimal driving with respect to an adaptation to the fuel composition, since different fuels or mixtures, for example, have a different penetration depth.

Further advantageous embodiments of the invention will become apparent from the dependent claims and the description.

Short description of the drawing

In the following embodiments of the invention will be explained in more detail with reference to the drawings. The same elements are provided in the various figures with the same reference numerals. The flow direction of the media is indicated by arrows.

Fig. 1

einen Brenner in perspektivischer Darstellung, teilweise aufgeschnitten;

Fig. 2

einen Schnitt durch die Ebene II-II in Fig. 1;

Fig. 3

einen Schnitt durch die Ebene III-III in Fig. 1;

Fig. 4

einen Schnitt durch die Ebene IV-IV in Fig. 1;

Fig. 5

einen erfindungsgemässen Brenner in perspektivischer Darstellung und mit Darstellung der Halbschalen;

Fig. 6

einen weiteren erfindungsgemässen Brenner mit Darstellung der Halbschalen und Mischrohr;

Fig. 7

einen Schnitt durch die Ebene VII-VII in Fig. 6.

Fig. 8

einen erfindungsgemässen Doppelkegelbrenner mit individuell regelbaren Brennstoffdüsen.

Show it:

Fig. 1

a burner in perspective, partially cut open;

Fig. 2

a section through the plane II-II in Fig. 1;

Fig. 3

a section through the plane III-III in Fig. 1;

Fig. 4

a section through the plane IV-IV in Fig. 1;

Fig. 5

a burner according to the invention in a perspective view and with representation of the half-shells;

Fig. 6

another inventive burner with representation of the half-shells and mixing tube;

Fig. 7

a section through the plane VII-VII in Fig. 6th

Fig. 8

a novel double-cone burner with individually controllable fuel nozzles.

Only the essential elements for the immediate understanding of the invention are shown, the sections are only a schematic, simplified representation of the burner.

Way to carry out the invention

The burner according to FIG. 1 consists of a swirl generator 30 which essentially consists of two half-hollow partial cone bodies 1, 2 which are offset from one another. Such a burner is referred to as a double-cone burner. The displacement of the respective central axis 1 b, 2 b of the partial cone bodies 1, 2 to each other on both sides in a mirror-image arrangement creates a respective tangential air inlet slot 19, 20, (Fig. 2-4), through which the combustion air 15 into the interior of the burner, ie in the conical cavity 14, also called swirl space, flows. The two partial cone bodies 1, 2 each have a cylindrical initial part 1a, 2a, which also analogously to the partial cone bodies 1, 2 offset from each other, so that the tangential air inlet slots 19, 20 are present from the beginning. In this cylindrical initial part 1 a, 2 a fuel lance 3 is arranged, which projects downstream into the swirl chamber 14. Of course, the burner can be purely conical, ie without cylindrical starting parts 1a, 2a. Both partial cone bodies 1, 2 each have a fuel line 8, 9, which are provided with openings 17 through which the gaseous fuel 13, which is mixed by the tangential air inlet slots 19, 20 flowing combustion air 15. The position of these fuel lines 8, 9 is schematically shown in Fig. 2-4. The fuel lines 8, 9 are attached to the end of the tangential air inlet slots 19, 20, so that there takes place the admixture 16 of the gaseous fuel 13 with the incoming combustion air 15. On the combustion chamber side in the combustion chamber 22, the burner at the burner outlet 29 a collar-shaped, as an anchor for the part cone body 1, 2 serving end plate 10 with a number of holes 11, through which dilution air or cooling air 18 the front part of the combustion chamber of the combustion chamber 22 and whose wall can be supplied. Ignition takes place at the top of the return flow zone 6. Only at this point can a stable flame front 7 arise. A flashback of the flame into the interior of the burner, as is latent in premixing lines, is less here.
In the design of the partial cone body 1, 2 with respect to conical tilt and the width of the tangential air inlet slots 19, 20 narrow limits are observed, so that the desired flow field of the air with its return flow zone 6 adjusts in the region of the burner mouth for flame stabilization. Generally it can be said that a reduction of the air inlet slots 19, 20 shifts the backflow zone 6 further upstream, whereby then however the mixture would come to the ignition earlier. After all, here is to say that the once geometrically fixed return flow zone 6 is stable in position, because the swirl number increases in the flow direction in the region of the conical shape of the burner.

The fuel lance 3 has openings 5, by means of which gaseous fuel can be injected into the swirl chamber 14 of the swirl generator. At the downstream end of the lance, a fuel injection 4 may be arranged, which may be, for example, an air-assisted nozzle or a pressure atomizer. By means of this fuel injection 4, additional liquid fuel can be injected. The lance 3 can also be subdivided into a plurality of regions so that individual injection of fuel can take place in these regions.

From Fig. 2 - 4 is also the position of the baffles 21 a, 21 b shown. They have flow initiation functions, wherein they extend, differently long, the respective end of the partial cone bodies 1 and 2 in the direction of flow of the combustion air 15. The channeling of the combustion air into the conical cavity 14 can be optimized by opening or closing the baffles 21 a, 21 b about the pivot point 23.

5, the swirl generator 30 consisting of the partial cone body 1 with the fuel line 8 and the partial cone body 2 with the fuel line 9 on the left side in the operating position and on the right side in a comparison position to compare the configuration of the two partial cone body shown , The openings 17a of the fuel line 8 are arranged asymmetrically with respect to the openings 17b of the fuel line 9. Fuel openings 17a are thus opposite areas of the fuel line 9, in which no fuel openings are arranged and fuel ports 17b are thus areas of the fuel line 8 opposite, in which no fuel ports are arranged. As a result, an asymmetric fuel profile is generated during the injection of the fuel into the combustion air. This asymmetric arrangement of the fuel openings 17a and 17a and the asymmetric fuel profile produced thereby suppresses pulsations. The type and strength of the generated asymmetry must be adapted to the special case. Burner system with few pulsations may have a low asymmetry of the fuel injection, in systems with high pulsations, the asymmetry must be increased.

FIG. 6 schematically shows a swirl generator, as is basically known from its function from EP 0 704 657 A2, the disclosure of which is hereby incorporated by reference. According to the invention, however, the fuel injection has now been adjusted. In principle, the burner shown here comprises a swirl generator 30 comprising two partial cone bodies 1, 2 and a mixing tube 50 arranged downstream, to which the combustion chamber 22 adjoins downstream. In the swirl chamber 14 protrudes in the downstream direction of the fuel lance 3. This has fuel injections 5. In this example, the lance and the fuel injections 5 are arranged in the swirl space such that the fuel injection takes place in the upper part of the swirl space 14. It is not shown that further injection openings can be arranged downstream in the lance, which can be addressed, for example, via separate fuel lines.
The openings 17 a of the fuel line 8 and the openings 17 b of the fuel line 9 are arranged in the downstream part of the swirl chamber 14. Fuel openings 17a and 17b are thus substantially opposite areas in which no fuel openings 5 are arranged in the lance 3. Thereby, a stepped introduction of the fuel via the lines 12 and 8 and 9 are generated. The injection via the openings 17a, 17b can of course also be asymmetric as described above in FIG.

The fuel distribution system of the external pilot fuel injection at the mixing tube 50 can be used for the fuel injection via the long lance 3.

FIG. 7 shows a cross section through the swirl generator from FIG. 6. The swirl generator here consists of four partial cone shells 1, 1 ', 2, 2' on which in each case in the region of the air inlet slots gas injection openings 17a, 17a ', 17b, 17b' are arranged. The gas outlet openings 5 of the lance are rotated at an angle Φ with respect to the gas injection openings 17a, 17a ', 17b, 17b'. The angle Φ can be adjusted so that a desired asymmetry is achieved. The rotation may also be 0 °, which means that there is no asymmetry, which may be advantageous for certain operating conditions. The adjustment of the angle Φ can also take place during operation, so that the desired asymmetry can be set in each operating state. For rotation of the lance this can be rotatably supported and via a drive 51, e.g. a stepping motor, are rotated, see FIG. 6.

FIG. 8 shows another embodiment of the double-cone burner according to the invention. The swirl space 14 is formed by the part cone shells 1 and 2. The combustion air flows via the air inlet slots 19 and 20 into the swirl chamber 14. In the region of the air inlet slots 19, 20, fuel ports 17a and 17b are arranged, via which fuel can be injected into the combustion air. The resulting fuel-air mixture is transported into the combustion chamber and ignited. At each air inlet slot 19, 20, the double-cone burner in this example each has eight fuel injection ports 17a and 17b, which are individually supplied with fuel via a conduit. In each of these lines, a valve 31 to 38, respectively 41 to 48 are arranged, each of which can be controlled independently of the other. In order to create an asymmetry, opposing fuel injection openings 17a and 17b are now controlled by means of the valves 31 and 41, 32 and 42, 33 and 43, etc., so that at least one of the eight opposite Pairs of fuel ports have a different fuel mass flow with respect to the opposite fuel port and so asymmetric fuel supply takes place.
The supply of fuel to the lance via two fuel lines, in each of which a fuel valve 39 and 49 is arranged. The lance is divided into a downstream part 3b and an upstream part 3a, which parts can each be independently supplied with fuel. Via the valve 39, the part 3b and via the valve 49 of the part 3a is controlled. By opening the valves 39 and 49, fuel can flow out through openings 5b and 5a into the swirl space. The parts 3a and 3b of the fuel lance can be rotated analogously to FIGS. 6 and 7. Advantageously, the rotation of the parts 3a and 3b can be independent of each other, whereby a higher degree of asymmetry is possible. Of course, the lance can be subdivided into other parts as described above, as described above.
Through sensors in the combustion chamber 22, the degree of pulsations can be determined and by means of the fuel injection ports 3a, 3b, 17a and 17b and the associated valve pairs 31 and 41, etc., and 39 and 49, the degree of asymmetry can be adapted to the circumstances. Of course, this control of asymmetry may be combined with staged combustion according to the disclosure of DE 100 64 893 A1, the disclosure of which is hereby incorporated, in order to more effectively prevent harmful pulsations.

When retrofitting existing plants or planning new plants, the external pilot fuel injection fuel distribution system can be used for fuel injection via the long lance. As is customary with internal burner fuel staging methods, all fuel injection stages are in operation at least under full load conditions.
Also, not only partially, as described above, on the injection in a Vormischkanal, ie an air inlet slot, but completely waived The injection of fuel would then be ensured via the lance.

Of course, the invention is not limited to the embodiment shown and described. Of course, the embodiment according to FIG. 5 can also be connected to the embodiment according to FIG. 8. As a result, the active control of the valves can be minimized.
Of course, the number of fuel holes and thus the number of valves can be arbitrarily adapted to the requirements. The burner may also have other shapes than shown in the embodiment and other types of burners may be used. The burner shown can be varied as desired with respect to the shape and size of the tangential air inlets 19, 20. The number of partial bodies of the swirl generator can be chosen arbitrarily.

LIST OF REFERENCE NUMBERS

1

Partial conical bodies

1a

cylindrical start part

1 b

Center axis Part cone body 1

2

Partial conical bodies

2a

cylindrical start part

2 B

Center axis Part cone body 2

3

fuel lance

3a

Fuel lance part upstream

3b

Fuel lance part downstream

4

fuel injection

5

Openings lance

5a

Openings lance upstream

5a

Openings lance downstream

6

backflow

7

flame front

8th

fuel line

9

fuel line

10

End plate

11

drilling

12

gaseous fuel

13

gaseous fuel

14

Cone cavity, swirl space

15

combustion air

16

admixture

17

openings

17a

Openings fuel line 8

17b

Openings fuel line 9

18

cooling air

19

Air inlet slot

20

Air inlet slot

21a

baffle

21b

baffle

22

combustion chamber

23

pivot point

29

burner outlet

30

swirl generator

31-38

Valves of the fuel nozzles at the first gap

39

Valves fuel nozzles lance 3b

41-48

Valves of the fuel nozzles at the second gap

49

Valves fuel nozzles lance 3a

50

mixing tube

51

stepper motor

Claims (13)

Premix burner, consisting essentially of a swirl generator (30) for a combustion air flow (15), fuel injection means (3, 5, 17, 17a, 17b, 31-38, 41-48) for introducing fuel into the combustion air flow (15) and air inlet slots (19, 20), via which the combustion air flow (15) enters a swirl space (14) of the swirl generator (30),
characterized,
in that the injection of the fuel into the combustion air takes place in a stepped manner via the fuel injection means (5, 5a, 5b, 17, 17a, 17b, 31-38, 41-48), at least one of the injection means (5, 5a, 5b) being connected to an injection means the swirl space projecting fuel lance (3, 3a, 3b) is arranged. Premix burner according to claim 1,
characterized,
that the injection means (5, 5a, 5b) of the projecting into the swirl chamber fuel lance (3) relative to injection nozzles (17, 17a, 17b, 31-38, 41-48) of the fuel are twisted at the swirler at an angle (Φ). Premix burner according to claim 1 or 2,
characterized,
that the swirl generator (30) at least two with respect to the symmetry of the swirl generator opposite the air inlet slots (19, 20). Premix burner according to claim 1, 2 or 3,
characterized,
in that at least part of the injection means (17, 17a, 17b, 31-38, 41-48) for introducing fuel into the combustion air flow (15) are arranged in the region of the air inlet slots (19, 20). Premix burner according to claim 1, 2, 3 or 4,
characterized,
in that fuel injection openings (17a, 17b) in the region of opposite air inlet slots (19, 20) are arranged at least partially asymmetrically in the flow direction as injection means, so that an asymmetry of the fuel injection openings (17a, 17b) is present. Premix burner according to one of the preceding claims,
characterized,
in that fuel injection openings (17a, 17b) can be supplied with fuel individually by control bodies (31-38, 41-48), in that at least one pair of substantially symmetrically opposed fuel injection openings (17a, 17b) are connected by associated control bodies (31 and 41, 32 and 42, etc.) are controlled such that more fuel emerges from one of the fuel injection port (17a) thus controlled than from the other fuel injection port (17b) associated with the pair. Premix burner according to one of the preceding claims,
characterized,
that the injection means (5, 5a, 5b) of the projecting into the swirl chamber fuel lance (3) relative to injection nozzles (17, 17a, 17b, 31-38, 41-48) of fuel at the swirl generator during the operation of the burner at an arbitrary angle (Φ ) are rotatable. Premix burner according to one of the preceding claims,
characterized,
in that the lance (3) is divided into at least two partial lances (3a, 3b) and that the fuel injection openings (5a, 5b) of the partial lances (3a, 3b) can be individually supplied with fuel by means of control bodies (39, 49). Premix burner according to one of the preceding claims,
characterized,
that the lance (3) in at least two lances (3a, 3b) is divided and that the partial lances (3a, 3b) are rotatable independently of each other by an arbitrary angle (Φ). Premix burner according to claim 6, 7, 8 or 9,
characterized,
that sensors for measuring pulsations are arranged in a combustion chamber (22) downstream of the swirl generator (30), and that the degree of asymmetry of the fuel injection can be set according to the intensity of the measured pulsations. Premix burner according to claim 6, 7, 8, 9 or 10,
characterized,
in that at least some of the symmetrically opposite pairs of fuel injection openings (17a, 17b) or fuel injections (5a, 5b) of the lance are actuated by the associated control bodies (31 and 41, 32 and 42, etc., 39, 49), which is in Flow direction stepped fuel profile can be generated. Premix burner according to one of the preceding claims,
characterized,
in that it is a double-cone burner with a swirl generator (30) consisting of at least two hollow partial cone bodies (1, 2) positioned on top of each other, which expand in the direction of flow and to one another are arranged offset so that the combustion air flow through the thus formed air inlet slots (19, 20) flows into the swirl chamber (14). Premix burner according to claim 12,
characterized,
in that a mixing tube (50) is arranged downstream of the swirl generator (30).

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