EP0851172B1 - Burner and method for operating a combustion chamber with a liquid and/or gaseous fuel - Google Patents

Description

Technical field

The present invention relates to a burner according to the preamble of claim 1.

State of the art

For burners for premix combustion of liquid and / or gaseous fuels forms the immigration the flame into the burner, also known as flashback, a major problem. In addition, the aerodynamics in these Burners are designed in such a way that local areas with a long in which ignite the fuel / air mixture can be avoided. Will a swirl flow generated so that high peripheral speeds near the axis occur, for example when radial Swirl registers are used, so is the axial speed low in the center. Because at the same time high levels of turbulence occur, the flame can move against the direction of flow spread out and then migrates into the burner, being subsequently general problems of overheating occur. In practice, this leads to restrictions 'the choice of swirl generation. The generation of a swirl flow field requires the flow to be enclosed in one preferably rotationally symmetrical space. The outer limitation this space creates a flow boundary layer, which always the condition of vanishing speed at the Has wall. The same applies to fuel lances installed in the center. The part of the mixture that is directly along the Wall flows, will remain in the burner for an undesirably long time. Step on the outer boundary of the swirl flow field particularly low speeds because at constant Total pressure in the arrangement of the static pressure from the inside rises to the outside, causing the dynamic pressure caused by the absolute speed is represented with increasing Radius is getting smaller. These low speeds may no longer be able to prevent the flame from the combustion chamber, along the boundary layer, into the burner. reproduces and can then overheat and destroy it.

From EP-B1-0 321 809 a burner has become known, which under Premixing conditions for liquid and / or gaseous Fuels the best known solution to date this area represents to the above shortcomings without having to implement additional equipment can.

However, the development in gas turbine construction goes that Vigorously increase compressor pressure ratios so that the Reliability of the above-mentioned burner from Reasons is automatically reduced.

The document DE-A1-44 09 918 describes a burner for operating a combustion chamber. This burner consists essentially of at least two hollow, conical ones Partial bodies whose axes of longitudinal symmetry are offset from one another, which means that they flow opposite air inlet slots for a combustion air flow arise. There is at least one nozzle in the cone cavity formed by the partial bodies for the introduction of a gaseous fuel. The burner points to the regularly arranged openings on the entire surface through which a gaseous Fuel with a certain calorific value is injected into the cone cavity. The Injection of the gas is injected at high speed, so that in front of the flame front a homogeneous mixture is present.

From US-A-3,958,416 is a premix burner with a convergent divergent Zone and a downstream reaction zone known. Air becomes initial swirled, mixed with fuel and passed through the burner. In the divergent There are holes in the area through which additional air is injected. That air is injected at right angles to the swirled air in order to further mix the Contribute fuel / air mixture, as the swirled air in this burner Layer formation tends.

Presentation of the invention

The invention seeks to remedy this. The invention how it is characterized in the claims, the task lies based on precautions for a burner of the type mentioned to meet those capable of a flashback to prevent safely.

The main advantage of the invention is that that this additional device of the simplest design is, and be installed as required in the burner mentioned can intervene without changing the basic concept of the same to have, with which such a burner, which is at medium compressor pressure ratios already well proven has, also for the further development stages of Gas turbines can be taken over and used.

According to the invention, additional air is injected along made of the burner walls, preferably in the downstream half of the burner. This additional air forms a film along the wall and mixes it then slowly with the fuel-enriched main flow. The essential improvement in security against one Backfire is based on two principles. On the one hand a weighty dilution of the mixture is carried out. There the burner is operating near its lean extinguishing limit weak local dilution of the mixture results along the walls to the desired loss of flammability of the mixture along the walls. On the other hand this additional air is injected so that the axial speed is increased along the wall, which is also convenient affects the operation of such a burner. In general is the pulse density ratio between film air and main flow in the range of 1 since both flows are common be accelerated from the same total pressure. Other impulses are also easily conceivable, they have striven for Effect no negative effects.

Advantageous and expedient developments of the inventive Task solutions are in the further dependent claims characterized.

In the following, exemplary embodiments will be described with reference to the drawings the invention explained in more detail. All for immediate understanding are not necessary elements of the invention been left out. The same elements are in the different Figures with the same reference numerals. The The direction of flow of the media is indicated by arrows.

Brief description of the drawings

Fig. 1

einen für eine Vormischverbrennung durch Bildung einer Drallströmung tauglichen Brenner, in perspektivischer Darstellung,

Fig. 2

eine weitere perspektivische Darstellung dieses Brenners, aus anderer Ansicht in vereinfachter Form.

Fig. 3

eine Abwicklung eines Teilkörpers mit Eindüsungsöffnungen für eine Zusatzluft,

Fig. 4

eine Konfiguration einer Einfachreihe von Eindüsungsöffnungen,

Fig. 5

eine Konfiguration einer Doppelreihe von Eindüsungsöffnungen und

Fig. 6, 7

eine spezielle Ausgestaltung der einzelnen Eindüsungsöffnungen.

It shows:

Fig. 1

a perspective view of a burner suitable for premix combustion by forming a swirl flow,

Fig. 2

another perspective view of this burner, from another view in simplified form.

Fig. 3

development of a partial body with injection openings for additional air,

Fig. 4

a configuration of a single row of injection openings,

Fig. 5

a configuration of a double row of injection openings and

6, 7

a special design of the individual injection openings.

WAYS OF IMPLEMENTING THE INVENTION, INDUSTRIAL APPLICABILITY

Fig. 1 shows a burner in a perspective view. For a better understanding of the subject, it is advantageous if at the same time when studying Fig. 1 based on the description Fig. 2 is also used.

1 consists of two hollow conical ones Partial bodies 1, 2, which are nested offset from one another are. The term "conical" here not just the one shown, with a fixed opening angle understood cone shape understood, but it closes also other configurations of the partial bodies, one such Diffuser or diffuser-like shape as well as a confuser or confuser-like shape. These forms are present not shown, since it is the person skilled in the art are common. The displacement of the respective central axis or Longitudinal axis of symmetry of the partial bodies 1, 2 to one another (see Fig. 2, Pos. 3, 4) creates on both sides, in mirror image Arrangement, each a tangential air inlet duct 5, 6 free, through which the combustion air 7 in the interior of the Brenners, i.e. flows into the cone cavity 8. The two tapered Partial bodies 1, 2 each have a cylindrical initial part 9, 10, which also, analogously to the aforementioned partial bodies 1, 2, offset to each other, so that the tangential Air inlet channels 5, 6 over the entire length of the Brenner are present. In the area of the cylindrical initial part is a nozzle 11 for preferably atomizing a liquid fuel 12 housed such that their injection approximately with the narrowest cross section of the the partial body 1, 2 formed conical cavity 8 coincides. The injection capacity and the operating mode of this Nozzle 11 depends on the given parameters of the respective Burner. The fuel injected through the nozzle 11 12 can be enriched with a recirculated exhaust gas if necessary become; then it is also possible through the nozzle 11 to provide the complementary injection of a quantity of water.

Of course, the burner can be purely tapered, i.e. without cylindrical initial parts 9, 10 may be formed. The partial body 1, 2 each have a fuel line 13, 14, which along the tangential inlet channels 5, 6 arranged and provided with injection openings 15, through which preferably a gaseous fuel 16 in the combustion air 7 flowing there is injected, as this is symbolized by arrows 16, these Injection at the same time the fuel injection level (see Fig. 3, item 22) of the system. These fuel lines 13, 14 are preferably at the latest at the end of the tangential inflow, before entering the cone cavity 8, placed this to ensure an optimal air / fuel mixture.

On the combustion chamber side, the burner has an anchor for the partial body 1, 2 serving front panel 18 with a number Bores 19 through which a mixing or Cooling air 20 or the front part of the combustion chamber 17 Wall is fed.

Liquid fuel 12 is used to operate the burner the central nozzle 11 is used, this is under one acute angle in the cone cavity 8 or in the combustion chamber 17 injected. A nozzle is thus formed from the nozzle 11 Fuel profile 23, which flows in from the tangential rotating combustion air 7 is enclosed. In axial Direction is the concentration of the fuel injected 12 continuously through the incoming combustion air 7 an optimal mixture degraded. If the burner with a operated gaseous fuel 16, this can in principle also happen via the fuel nozzle 11, preferably but this is done via the injection openings 15, wherein the formation of this fuel / air mixture right at the end the air inlet channels 5, 6 comes about.

When the liquid fuel 12 is injected via the nozzle 11 becomes the optimal, homogeneous fuel concentration at the end of the burner reached over the cross section. Is the Combustion air 7 additionally preheated or with a recirculated Exhaust gas enriched, this supports the evaporation of liquid fuel 12 sustainable, namely within the premix distance induced by the length of the burner.

The same considerations also apply when using the fuel lines 13, 14 instead of gaseous liquid fuels should be fed.

When designing the conical part body 1, 2 with respect the increase in the flow cross section and the The width of the tangential air inlet channels 5, 6 are adhere to narrow limits so that the desired Flow field of the combustion air 7 at the outlet of the burner can adjust. The critical swirl number arises at the exit of the burner: A backflow zone also forms there or backflow bladder 24 (vortex breakdown) with one opposite the flame front 25 acting there stabilizing Effect one, in the sense that the backflow zone 24 has the function of a disembodied flame holder.

The optimal fuel concentration across the cross-section is only in the area of vertebral bursting, i.e. in the area the backflow zone 24 reached. Only at this point then a stable flame front 25. The flame stabilizing Effect results from the cone cavity 8 forming swirl number in the direction of flow along the cone axis. The flame strikes back inside the burner therefore occurs due to this fluidic specification not on.

Generally it can be said that minimizing the flow opening of the tangential air inlet ducts 6, 7 is predestined is the backflow zone 24 from the end of the premixing section to build. The construction of the burner is suitable furthermore excellent, the flow opening of the tangential To change air inlet channels 5, 6 as required, with what a relative without changing the overall length of the burner large operational bandwidth can be captured. Of course are the partial body 1, 2 in another Plane can be shifted towards each other, which even overlaps opposite the air inlet plane into the cone cavity 8 (See FIG. 2, item 21) of the same in the area of the tangential Air inlet channels 5, 6, as shown in Fig. 2, accomplished can be. It is then also possible that Partial body 1, 2 by a counter-rotating movement to nest in a spiral.

Through a more homogeneous mixture formation that can be achieved in this burner between the injected fuels 11, 12 and Combustion air 7 achieves lower flame temperatures and thus lower pollutant emissions, especially lower ones NOx. Then these lower temperatures reduce the thermal Load on the material on the burner front and make for example, no special treatment of the surface absolutely necessary.

As for the number of air intake ducts, that is Burner not limited to the number shown. A bigger one For example, number is shown where it matters goes to make the premixing wider, or the swirl number and thus the dependent formation of the backflow zone 24 by a larger number of air inlet channels accordingly to influence. In this context, EP-A2-0 704 657 referenced, this document integrating Is part of this description.

Fig. 2 shows the same burner according to Fig. 1 but from a different one Perspective and in a simplified form. This figure 2 mainly wants the disposition of the two conical ones Show part body 1, 2 and their offset to each other. The Displacement of the respective central axis 3, 4 of the two partial bodies to each other, based on the main central axis 26 of the Burner, which is the main axis of the central fuel nozzle 11 corresponds to the respective size of the flow openings the tangential air inlet ducts 5, 6. The central axes 3, 4 run parallel to each other here. In this figure are furthermore associated with each partial body 1, 2 Zone 27 in which the placements of Means for the injection of additional air takes place. For the individual configurations of these funds are based on the following Figures 3-7 referenced.

3 shows a development 28 of a conical partial body, which schematically shows zone 27 within which has a specific configuration of injection openings for additional air, which ensure a reignition lock, is taken as a basis. The orientation of the injection openings 29 as well as their number and size will be the respective Flow conditions in the burner adjusted. The final Purpose is primarily aimed at the reignition barrier. The individual oblique lines 30 want the placement of the symbolize individual rows of the injection openings 29. The arrows 31 point to the outflow direction of the Additional air indicate that is at right angles to the Level 30 of the injection openings 29 runs. This outflow direction can, however, range from purely axial to direction the main flow vary. For better understanding are in this processing 28 a single row and one Double row of injection openings 29 shown. The corresponding cuts are then shown in FIGS. 4 and 5.

Fig. 4 shows the design of a simple row of injection openings 29. The additional air 32 is here under one injected acute angle with respect to the swirl flow 7a, that is flat to the inner wall of the corresponding partial body 2, this around improve film production.

5 shows a double row of injection openings 29. Basically, the same precautions are taken here as described in Fig. 3.

6, the injection openings 33 run in the area the inner wall of the corresponding partial body 2 fan-shaped, as shown in Fig. 7, which is a plan view.

Basically there is a wide variation in the design of the Injection openings possible. For currents with a pronounced high swirl there are restrictions on the arrangement of the injection openings. As long as you use holes you can go through the desired injection direction Determine the orientation of the holes. However, slots have to be are often segmented for reasons of component strength.

It should also be emphasized that the flashback barrier proposed here not limited to the burner described here is. This backfire intervenes wherever premix combustion by generating a swirl flow field is taken as a basis.

LIST OF REFERENCE NUMBERS

1

Partial conical body

2

Partial conical body

3

Central axis to 1

4

Central axis to 2

5

Tangentialwer air inlet duct

6

Tangential air inlet duct

7

combustion air

7a

swirl flow

8th

Cone cavity, interior of the burner

9

Cylindrical starting part of the burner

10

Cylindrical starting part of the burner

11

fuel nozzle

12

Fuel, liquid fuel

13

fuel line

14

fuel line

15

Injection openings of a fuel line 13, 14

16

Fuel, gaseous fuel

17

combustion chamber

18

front panel

19

Holes in the front panel

20

Air, mixed air, cooling air

21

Air Intake Level

22

Fuel injection plane

23

fuel profile

24

Backflow zone, backflow bubble

25

flame front

26

Main central axis

27

Eindüsungszone

28

Development of a conical part of the body

29

injection openings

30

Level of the injection openings 29

31

Outflow injection direction of the additional air

32

additional air

33

Fan-shaped injection openings

Claims (16)

1. Burner for operating a combustion chamber with a liquid and/or gaseous fuel (12, 16), the burner comprising at least two hollow, conical sectional bodies (1, 2) nested one inside the other in the direction of flow, the centre axes (3, 4) of these sectional bodies (1, 29 [sic]) running offset from one another, the adjacent walls of the sectional bodies (1, 2) forming tangential air-inlet ducts (5, 6) for combustion air (7), and there being at least one fuel nozzle (11, 15) in the conical hollow space (8) formed by the sectional bodies (1, 2), characterized in that at least one sectional body (1, 2) has at least one zone (27), within which there are a number of injection openings (29, 33) for injecting supplementary air (32), these injection openings (29, 33), as viewed in the direction of flow of the burner, being at an acute angle to the inner wall of the sectional body (1, 2).
2. Burner according to Claim 1, characterized in that a number of spaced-apart fuel nozzle [sic] (15) are arranged in the region of the tangential air-inlet ducts (5, 6) in the longitudinal extent of the burner.
3. Burner according to Claim 1, characterized in that the conical hollow space (8) increases uniformly in the direction of flow.
4. Burner according to Claim 1, characterized in that the conical hollow space (8) forms a diffuser, a diffuser-like profile, a confuser, a confuser-like profile in the direction of flow.
5. Burner according to Claim 1, characterized in that the sectional bodies (1, 2) are nested spirally one inside the other.
6. Burner according to one of Claims 1 to 5, characterized in that each sectional body (1, 2) has at least one zone (27).
7. Burner according to one of Claims 1 to 5, characterized in that the injection openings (29, 33) form a plurality of rows (30), spaced apart in parallel, inside the at least one zone (27).
8. Burner according to one of Claims 1 to 5, characterized in that the injection openings (29, 33) are fan-shaped.
9. Burner according to one of Claims 1 to 5, characterized in that the injection openings (29, 33) are arranged in a direction which extends from the axial direction of the burner up to the direction of the main flow.
10. Burner according to one of Claims 1 to 5, characterized in that the injection openings (29, 33) are delegated [sic] in the second half of the burner on the outflow side.
11. Burner according to one of Claims 1 to 5, characterized in that the injection openings (29, 33) are injection slots.
12. Method of operating a burner according to one of Claims 1 to 11, the burner comprising at least two hollow, conical sectional bodies (1, 2) nested one inside the other in the direction of flow, the centre axes (3, 4) of these sectional bodies (1, 29 [sic]) running offset from one another, the adjacent walls of the sectional bodies (1, 2) forming tangential air-inlet ducts (5, 6), and there being at least one fuel nozzle (11, 15) in the conical hollow space (8) formed by the sectional bodies (1, 2),

    a) combustion air (7) flowing through the tangential air-inlet ducts (5, 6) into a premix section formed by the sectional bodies (1, 2),

    b) at least one fuel (12, 16) being injected through the at least one fuel nozzle (11, 15) into the conical hollow space (8), and

    c) a swirl flow (7a) being formed in the conical hollow space (8) of the burner by the combustion air (7) and the fuel (12, 16),

    characterized in that at least one sectional body (1, 2) has at least one zone (27), within which supplementary air (32) is injected through injection openings (29, 33) into the swirl flow (7a) at an acute angle, as viewed in the direction of flow of the burner, to the inner wall of the sectional body (1, 2) for forming a film along the inner wall.
13. Method according to Claim 12, characterized in that the supplementary air (32) is injected in the second half of the burner on the outflow side.
14. Method according to Claim 12 or 13, characterized in that the supplementary air (32) is injected into the swirl flow (7a) inside the at least one zone (27) in a plurality of rows (30) spaced apart in parallel.
15. Method according to one of Claims 12 to 14, characterized in that the supplementary air (32) is injected in a direction which extends from the axial direction of the burner up to the direction of the main flow.
16. Method according to one of Claims 12 to 15, characterized in that the axial velocity along the inner wall of the sectional body (1, 2) is increased by the injection of the supplementary air (32).

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