EP1645802B1 - Premix Burner - Google Patents

Description

Technical area

The invention is based on a premix burner according to the preamble of the independent 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, these limitations are accompanied by thermoacoustic oscillations. 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 out of the EP 0 321 809 A1 known pilot burner, a so-called double-cone burner, this pilot burner is realized by fuel in the center of the swirl body, here called double cone, injected. 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 the EP 0 704 657 A2 Another 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 flows after the burner exit. The escaping gas burns in a stabilized by the jump in cross section at the burner outlet flame.

Both in the execution of the external pilot according to the EP 0 704 657 A2 as well as internal piloting according to EP 0 321 809 B1 can not be guaranteed over the entire load range optimal injection of the fuel to achieve lowest pollutant emissions.

From the WO 01/96785 A1 , of the DE 10064893 and the DE 10164099 burners are known with stepped premix gas injection, 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 are fed independently with premix gas. According to the WO 01/96785 the outlet openings on the swirl body and on the lance can be arranged so that no outlet openings are arranged at the arranged on the lance outlet openings opposite to the swirl body.

In further development of these solutions of a graded fuel injection teaches WO 2002061335 an individual control of arranged in different axial positions fuel inlet openings by the inlet openings are each associated with an axial plane of a separate control body. In this way, it is possible to additionally control the mass flow distribution of the fuel introduced into the premix burner and thus to further optimize the combustion process with regard to combustion chamber pulsations and NO _x emissions.

The publication DE 10160907 teaches to reduce the introduction of thermoacoustic vibrations, the fuel in the combustion air flow so that the speed of the fuel of that of the combustion air flow is adjusted. On the one hand, a change in the exit velocity of the fuel causes a change in the fuel / combustion air mixing profile, and on the other hand, it influences the time delay τ, ie the time it takes for mixture fractional fluctuations to be converted into the flame.

After document EP 1336800 is the stability of the backflow zone of a premix burner of the EP 321809 described another important criterion for the formation of thermoacoustic vibrations. By stabilizing the Rückströmzone and the reduction of the formation of coherent vortex structures at the burner outlet thermoacoustic oscillations causing periodic heat release within the combustion chamber can be reduced. EP 1336800 discloses a series of measures on the central fuel lance, which cause a fluidic stabilization of the return flow zone. These measures include the axial arrangement of the fuel outlets as well as the design of the end portion of the fuel lance.

Presentation of the invention

The invention has for its object to provide a premix burner of the type mentioned, which ensures optimal injection of the fuel over the entire load range and thermoacoustic vibrations is able to suppress even more effective.

According to the invention this is achieved by a premix burner of the type described in independent claim 1.

The core of the invention is to achieve a stepped injection of the fuel into the combustion air by arranging a projecting into the swirl space fuel lance, characterized in that the Brennstoffindüsungsmittel on the fuel lance against the injections of the fuel at the swirl generator by an angle (Φ) are rotatable, wherein the fuel lance is divided into at least two partial lances, the fuel injection openings of the partial lances are individually supplied by fuel control body, and the partial lances are independently rotatable by the angle (Φ).

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 take place statically, in that no injection opening is arranged in the region opposite to an injection opening. 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. Opposite fuel injection openings are then supplied by means of the control 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 Brenner in perspektivischer Darstellung und mit Darstellung der Halbschalen;

Fig. 6

einen weiteren 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 level III-III in Fig. 1 ;

Fig. 4

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

Fig. 5

a burner in perspective and with representation of the half-shells;

Fig. 6

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

Fig. 7

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

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 premix burner according to Fig. 1 consists of a swirl generator 30, which consists essentially of two half hollow cone bodies 1, 2, which are offset from each other, is constructed. 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 body 1, 2 to each other creates on both sides in a mirror-image arrangement each have a tangential air inlet slot 19, 20, ( Fig. 2-4 ), through which the combustion air 15 in 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 schematic Fig. 2-4 out. 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 anchorage for the part cone body 1, 2 serving end plate 10 with a number of holes 11, through which if necessary 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.

When designing the partial cone bodies 1, 2 with regard to the conical inclination and the width of the tangential air inlet slots 19, 20, strict limits must be observed so that the desired flow field of the air with its backflow zone 6 in the region of the burner mouth is established 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's to say that 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 3, a fuel injection 4 can be arranged, which can be, for example, an air-assisted nozzle or a pusher sprayer , By means of this fuel injection 4, additional liquid fuel can be injected. The lance 3 is divided into several areas, so that in these areas an individual injection of fuel can take place.

Out Fig. 2-4 is also the location of the baffles 21 a, 21 b out. 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.

In Fig. 5 is the swirl generator 30 consisting of the part cone body 1 with the fuel line 8 and the part 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 part 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 openings 17b are thus opposite areas of the fuel line 8, in which no fuel openings 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 produced 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.

In the Fig. 6 is schematically shown a swirl generator, as he basically from his function from the EP 0 704 657 A2 is known. 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. The lance 3 and the fuel injections 5 are arranged in this example in the swirl chamber 14, that the fuel injection takes place in the upper part of the swirl chamber 14. It is not shown that in the lance 3 further injection openings are arranged downstream, 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 as above in the Fig. 5 described asymmetrically.

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.

In Fig. 7 is a cross section through the swirl generator Fig. 6 shown. 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 at an angle Φ relative to the gas injection openings 17a, 17a ', 17b, 17b' twisted. 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. To rotate the lance, it can be rotatably mounted and rotated by a drive 51, for example a stepping motor, see Fig. 6 ,

In Fig. 8 schematically a longitudinal section through the swirl chamber 14 is shown. 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. To create an asymmetry, opposing fuel injection ports 17a and 17b are now driven by valves 31 and 41, 32 and 42, 33 and 43, etc. so that at least one of the eight opposing pairs of fuel ports will have a different fuel mass flow relative to the fuel port opposite it has and thus an 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 over the openings 5b and 5a flow into the swirl chamber 14. The parts 3a and 3b of the fuel lance can be analogous to 6 and 7 to be twisted. 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 divided into even more parts as needed.

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. This control of asymmetry may, of course, be with a staged combustion according to the disclosure of DE 100 64 893 A1 , the disclosure of which is hereby incorporated, combined 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, could be applied to injection in a premix channel, i. an air inlet slot, but completely dispensed with, the injection of fuel would then be guaranteed via the lance.

Of course, the invention is not limited to the embodiment shown and described. The execution after Fig. 5 Of course, it can also be done with the execution Fig. 8 get connected. 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 with respect to the Shape and the size of the tangential air inlets 19, 20 can be varied as desired. The number of partial bodies of the swirl generator can be chosen arbitrarily.

LIST OF REFERENCE NUMBERS

1

Partial conical bodies

1a

zylindrischerAnfängsteil

1b

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

5b

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 (9)

1. Premix burner, essentially consisting 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), wherein the fuel is injected into the combustion air via the fuel injection means (5, 5a, 5b, 17, 17a, 17b, 31-38, 41-48) in stages, and wherein at least one of the injection means (5, 5a, 5b) is arranged on a fuel lance (3) projecting into the swirl space and can be rotated on the swirl generator by an angle (Φ) with respect to the injection points (17, 17a, 17b, 31-38, 41-48) of the fuel, characterized in that the fuel lance (3) is divided into at least two part lances (3a, 3b), in that fuel injection openings (5a, 5b) of the part lances (3a, 3b) can be supplied with fuel individually by regulating bodies (39, 49), and in that the part lances (3a, 3b) can be rotated by the angle (Φ) independently of one another.
2. Premix burner according to Claim 1,
   characterized in that
   the swirl generator (30) has at least two air inlet slots (19, 20) opposite one another with respect to the symmetry of the swirl generator.
3. Premix burner according to Claim 1 or 2,
   characterized in that
   at least one part of the injection means (17, 17a, 17b, 31-38, 41-48) for introducing fuel into the combustion air flow (15) is arranged in the region of the air inlet slots (19, 20).
4. Premix burner according to Claim 1, 2 or 3, characterized in that
   as injection means fuel injection openings (17a, 17b) are arranged at least partially asymmetrically in the flow direction in the region of mutually opposite air inlet slots (19, 20), such that there exists an asymmetry of the fuel injection openings (17a, 17b).
5. Premix burner according to one of the preceding claims,
   characterized in that
   fuel injection openings (17a, 17b) can be supplied with fuel individually by regulating bodies (31-38, 41-48), in that at least one pair of essentially symmetrically mutually opposite fuel injection openings (17a, 17b) are controlled by associated regulating bodies (31 and 41, 32 and 42, etc.) such that more fuel comes out of one of the fuel injection openings (17a) controlled in this manner than out of the other fuel injection opening (17b) belonging to the pair.
6. Premix burner according to Claim 1,
   characterized in that
   in a combustion chamber (22) downstream of the swirl generator (30), there are arranged sensors for measuring pulsations, and in that the degree of asymmetry of the fuel injection can be set depending on the strength of the measured pulsations.
7. Premix burner according to Claim 1,
   characterized in that
   at least some of the symmetrically opposite pairs of fuel injection openings (17a, 17b) or fuel injection openings (5a, 5b) of the lance (3) are controlled by the associated regulating bodies (31 and 41, 32 and 42, etc., 39, 49) such that it is possible to generate a fuel profile that is stepped in the flow direction.
8. Premix burner according to one of the preceding claims,
   characterized in that
   it is a double-cone burner with a swirl generator (30) made up of at least two hollow partial conical bodies (1, 2) which are positioned one on the other, which broaden in the flow direction and which are arranged offset with respect to one another, such that the combustion air flow flows into the swirl space (14) via the air inlet slots (19, 20) so formed.
9. Premix burner according to Claim 8,
   characterized in that
   a mixing pipe (50) is arranged downstream of the swirl generator (30).

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