EP0881431A2 - Burner for operating a hot gas generating unit - Google Patents

Abstract

In a burner for operating a unit for generating a hot gas, guide bodies (50) are arranged in the interior (8) formed by a number of part bodies (1, 2), which act on the inner walls of these part bodies. These guide bodies (50) preferably have the shape of guide vanes and ensure that the combustion air (7) flowing largely tangentially into the interior (8) is deflected in the direction of flow. This deflection to an axial component of the flow within the interior (8) takes place gradually, the degree depending on the predetermined flow angles (α, αn) of the guide bodies (50). This maximizes the mixture quality of the combustion air (7) and strengthens the positional stability of the return flow zone at the burner outlet. <IMAGE> <IMAGE>

Description

Technical field

The present invention relates to a burner for operating an assembly for Generation of a hot gas according to the preamble of claim 1.

State of the art

The flame stabilization of many modern low NOx burners, as in EP-B1-0 321 809, is based on the creation of a backflow zone or backflow bubble (= Vortex breakdown). These burners are often referred to as premix burners, based on the fact that the premix of the used coming fuel made within a distance belonging to the burner becomes. With an unfavorable design of the swirl generator resp. the swirl formation Such a premix burner has the desired high number of swirls short backflow zone due to the bursting of the vortex into a long one almost cylindrical backflow zone over. When operating such a premix burner without a subsequent combustion chamber, or if the combustion chamber is too large, resp. in a combustion chamber, the combustion chamber walls of which are relatively cold, what is typically the case with boilers becomes the backflow Flue gases in the core extracted the heat. This leads, especially at the start, insufficient flame stabilization, and when operating the premix burner with a liquid fuel to insufficient pre-evaporation the fuel drop. This behavior can also be seen with burners for Detect boiler systems with passive flue gas recirculation in the combustion chamber. These problems can cause the flame to burst or vibrate, and make an undesired special starting procedure necessary. For heating systems a very long start-up phase must also be provided, which leads to increased pollutant emissions. This essentially depends together with the fact that the entire boiler with its relatively large thermal Inertia must be warmed up until the back-flowing exhaust gases have a sufficient temperature.

a) Erhöhung der Gefahr eines Flammenrückschlages ins Innere des Vormischbrenners;

b) aus a) ergibt sich dann die Konsequenz, dass der Betriebsbereich mit einer optimalen Flammenposition beschränkt bleibt;

c) die Verbrennung ist Pulsationen unterworfen, die mannigfaltig zu einer Destabilisierung der Flammenposition und/oder zu einer Erhöhung der Schadstoff-Emissionen, insbesondere der NOx-Emissionen führen;

d) es entstehen grosse Abweichungen hinsichtlich der optimalen Strömungsbedingungen, wodurch das Potential des Vormischbrenners nicht vollständig ausgenutzt werden kann;

e) das Startprozedere ist aus obengenannten Unzulänglichkeiten problematisch zu handhaben.

For the premix burner itself, with such a constellation and with certain operating modes of the burner, the following imperfections or Shortcomings:

a) increasing the risk of a flashback inside the premix burner;

b) from a) there follows the consequence that the operating range remains limited with an optimal flame position;

c) the combustion is subject to pulsations which in many ways lead to the destabilization of the flame position and / or to an increase in pollutant emissions, in particular NOx emissions;

d) large deviations arise with regard to the optimal flow conditions, as a result of which the potential of the premix burner cannot be fully utilized;

e) the starting procedure is difficult to handle due to the above-mentioned shortcomings.

Presentation of the invention

The invention seeks to remedy this. The invention as set out in the claims is characterized, the task is based on a burner at the beginning to submit proposals that address the above imperfections and to remedy shortcomings.

The main advantage of the invention is that the main body of the burner remains essentially unchanged. Just to fix the disadvantages mentioned above as well as to strengthen themselves at the exit of the burner Backflow zone forming have the inner walls of those forming the burner Shells built-in guide bodies, which take over the task, in advance the combustion air flowing purely tangentially into the interior of the burner, which preferably consists of an air / exhaust gas mixture, in the axial direction redirect. The inflow angle of this guide body, which preferably are designed as guide vanes, seen from the burner tip in the direction of flow. In the area of the burner outlet, these guide bodies have up to a vertical position with respect to the burner axis. So that these Guides can work properly, their number will be within the length of the Brenners chosen so that the ratio between the distance of the guide body to each other and the width of the tangential inflow channel into the interior of the Brenners is approximately 1.

Advantageous and expedient developments of the task solution according to the invention are characterized in the further dependent claims.

Exemplary embodiments of the invention are described below with reference to the drawings explained in more detail. None for the immediate understanding of the invention necessary elements have been omitted. The same elements are in the different figures with the same reference numerals. The flow direction the media is indicated by arrows.

Brief description of the drawings

Fig. 1

einen Vormischbrenner in perspektivischer Darstellung,

Fig. 2

eine weitere perspektivische Darstellung des Vormischbrenners gemäss Fig. 1, aus anderer Ansicht, in vereinfachter Form,

Fig. 3

einen radialen Schnitt durch den Vormischbrenner mit Ansicht der Injektoren,

Fig. 4

einen axialen Schnitt durch den Vormischbrenner gemäss Fig. 3, mit parallelem Verlauf der Lochplatten gegenüber den Einströmungsebenen, mit Darstellung von Leitschaufeln im Innenraum des Vormischbrenners,

Fig. 5

einen weiteren radialen Schnitt durch den Vormischbrenner mit Ansicht der Injektoren und

Fig. 6

einen axialen Schnitt durch den Vormischbrenner gemäss Fig. 5 mit einer weiteren Konfiguration der Injektoren in Strömungsrichtung.

It shows:

Fig. 1

a premix burner in perspective,

Fig. 2

1, another perspective view of the premix burner according to FIG. 1, in a simplified form,

Fig. 3

a radial section through the premix burner with a view of the injectors,

Fig. 4

3 shows an axial section through the premix burner according to FIG. 3, with the perforated plates running parallel to the inflow planes and showing guide vanes in the interior of the premix burner,

Fig. 5

another radial section through the premix burner with a view of the injectors and

Fig. 6

an axial section through the premix burner according to FIG. 5 with a further configuration of the injectors in the flow direction.

WAYS OF CARRYING OUT THE INVENTION, INDUSTRIAL APPLICABILITY

Fig. 1 shows a premix burner in perspective. For the better Understanding the subject matter is beneficial if at the same time when capturing of Fig. 1 at least also Fig. 2, possibly Fig. 3 are used. The the first-mentioned figures have mainly the purpose, the type and the functioning of such a burner.

The premix burner according to FIG. 1 consists of two hollow conical partial bodies 1, 2, which are nested offset from one another. That burner is operated with a gaseous and / or liquid fuel. Under the The term "cone-shaped" here is not only that shown by a fixed opening angle understood cone shape understood, but it also closes other configurations of the partial body, such as a diffuser or diffuser-like Shape, as well as a confuser or confuser-like shape. These forms are not specifically shown here, since they are familiar to the person skilled in the art are. The offset of the respective central axis or longitudinal axis of symmetry Partial body 1, 2 to each other (see Fig. 2, Pos. 3, 4) creates on both sides, in mirror-image arrangement, each one tangential air inlet duct 5, 6 free, through which the combustion air 7 in the interior of the premix burner, i.e. in the cone cavity 8 flows. The two conical partial bodies 1, 2 each have one cylindrical initial part 9, 10, which also, analogous to the aforementioned partial bodies 1, 2, offset from each other, so that the tangential air inlet channels 5, 6 are present over the entire length of the premix burner. In the area of the cylindrical initial part is a nozzle 11 for preferential atomization a liquid fuel 12 housed such that their injection approximately with the narrowest cross section of that formed by the partial bodies 1, 2 Cone cavity 8 coincides. The injection capacity and the operating mode this nozzle 11 depends on the given parameters of the respective Premix burner. The fuel 12 injected through the nozzle 11 can if necessary, be enriched with a recirculated exhaust gas; then it is also possible, through the nozzle 11, the complementary injection of an amount of water to accomplish.

Of course, the premix burner can be purely conical, i.e. without a cylindrical one Initial parts 9, 10 may be formed. The sub-bodies 1, 2 also each have one Fuel line 13, 14, which runs along the tangential inlet channels 5, 6 are arranged and provided with injection openings 15, through which preferably a gaseous fuel 16 in the combustion air flowing there 7 is injected, as is symbolized by arrows 16, wherein this injection also the fuel injection level (see FIG. 2, item 22) of the Systems forms. These fuel lines 13, 14 are preferably at the latest placed at the end of the tangential inflow, before entering the cone cavity 8, this to ensure an optimal air / fuel mixture.

On the combustion chamber side, the premix burner has an anchorage for the partial bodies 1, 2 serving front panel 18 with a number of holes 19 through which if necessary, a mixed or cooling air 20 the front part of the combustion chamber 17th or whose wall is fed.

If, as already described, the premix burner is used solely by means of a liquid Operated fuel 12, this is done via the central nozzle 11, wherein this fuel 12 then enters the cone cavity 8 at an acute angle or is injected into the combustion chamber 17. The nozzle 11 thus forms a tapered fuel profile 23 rotating from the tangentially flowing Combustion air 7 is enclosed. In the axial direction, the concentration of the injected fuel 12 continuously through the incoming combustion air 7 broken down into an optimal mixture.

If you want to operate the premix burner with a gaseous fuel 16, so this can in principle also be done via the central fuel nozzle 11, however, such an operating mode should preferably be via the injection openings 15 be made, the formation of this fuel / air mixture directly at the end of the air inlet ducts 5, 6.

When the liquid fuel 12 is injected via the nozzle 11, the end the premix burner the optimal, homogeneous fuel concentration over the Cross section reached. Is the combustion air 7 additionally preheated or with a recycled exhaust gas enriched, this supports the evaporation of the liquid fuel 12 sustainably within the length of the premix burner induced premixing. As for the admixture of a returned Flue gas is concerned, so reference is made to Fig. 3-6.

The same considerations also apply if the fuel lines 13, 14 instead of gaseous liquid fuels should now be supplied.

In the design of the conical part body 1, 2 with respect to the increase the flow cross-section and the width of the tangential air inlet ducts 5, 6 are strict limits to be observed so that the desired flow field the combustion air 7 at the outlet of the premix burner can. The critical swirl number is set at the outlet of the premix burner: A backflow zone 24 (vortex breakdown) also forms there with one opposite the flame front 25 acting there stabilizing effect, in which Meaning that the backflow zone 24 functions as a disembodied flame holder takes over.

The optimal fuel concentration across the cross section is only in the area the vortex runout, that is, in the area of the backflow zone 24. First a stable flame front 25 then arises at this point.

In general it can be said that minimizing the flow opening of the tangential Air inlet channels 6, 7 is predestined, the backflow zone 24 from the end of Form premixing section. The design of the premix burner is suitable furthermore excellent, the flow opening of the tangential air inlet ducts 5, 6 to change as required, which means without changing the overall length of the premix burner a relatively large operational bandwidth can be covered. Of course, the partial bodies 1, 2 are also in a different plane to one another displaceable, which even overlaps the above the air inlet plane into the cone cavity 8 (see FIG. 2, item 21) in the same Area of the tangential air inlet ducts 5, 6, as can be seen from FIG. 2, can be accomplished. It is then also possible to pass through the partial bodies 1, 2 to interleave a counter-rotating movement in a spiral.

Through a more homogeneous mixture formation achievable in this premix burner achieved between the injected fuels 11, 12 and the combustion air 7 lower flame temperatures and thus lower pollutant emissions, in particular lower NOx values. Then reduce these lower temperatures the thermal load on the material on the burner front and make for example special treatment of the surface is not mandatory.

As far as the number of air inlet ducts is concerned, the premix burner is not open the number shown is limited. A larger number is displayed there, for example, when it comes to making the premixing wider, or the Swirl number and thus the dependent formation of the backflow zone 24 by to influence a larger number of air inlet ducts accordingly.

Premix burners of the type described here are also those for which Achieving a swirl flow from a cylindrical or quasi-cylindrical It is assumed that the combustion air flows into the interior of the pipe Pipe via tangentially arranged air inlet ducts, and inside the tube a conical body with decreasing in the direction of flow Cross-section is arranged, which also with this configuration critical swirl number can be achieved at the outlet of the burner.

FIG. 2 shows the same premix burner according to FIG. 1, but from a different one Perspective and in a simplified representation. This Fig. 2 is essentially serve to correctly record the configuration of this premix burner. In particular, this FIG. 2 shows the displacement of the two partial bodies 1, 2 from one another, in relation to the main central axis 26 (= burner axis) of the premix burner, which corresponds to the main axis of the central fuel nozzle 11, quite clearly visible. This offset is a measure of the size of the flow width resp. the flow cross section of the tangential air inlet ducts 5, 6. The respective central axes 3, 4 run parallel to one another here.

Fig. 3 is a section approximately in the middle of the premix burner. The mirror image Tangentially arranged feed channels 27, 28 each perform the function of a Mixing section in which the combustion air 7, which consists of fresh air 29 and recirculated flue gas 30 is formed, is perfected. The combustion air 7 is processed in an injector system 200. Upstream of each feed channel 27, 28, as a tangential inflow into the interior 8 of the premix burner serves, the fresh air 29 over the entire length of this premix burner evenly distributed over perforated plates 31, 32. In the direction of flow to the tangential Inlet channels 5, 6, these perforated plates 31, 32 are perforated. The perforations perform the function of individual injector nozzles 31a, 32a, which have a suction effect exercise against the surrounding flue gas 30 such that each of these Injector nozzle 31a, 32a only sucks in a certain proportion of flue gas 30, whereupon over the entire axial length of the perforated plates 31, 32, that of the burner length corresponds, a uniform flue gas admixture takes place. This Configuration means that the two media, ie the Fresh air 29 and the flue gas 30, an intimate mixing takes place, so that the flow length extending up to the tangential air inlet ducts 5, 6 of the feed channels 27, 28 can be minimized for the mixture formation can. In addition, the local injector configuration 200 is characterized by that the geometry of the premix burner, especially what the shape and the Concerns the size of the tangential air inlet ducts 5, 6, remains dimensionally stable, i.e. by along the evenly metered distribution of the hot smoke gases 30 along The entire axial length of the premix burner does not result in any heat-related Faults. The same injector configuration as the one just described here can also in the area of the head-side fuel nozzle 11 for a axial supply of combustion air can be provided. The feed channels 27, 28 also have guide plates 50, which are described in the description of FIGS Fig. 4 is discussed in more detail.

FIG. 4 is a schematic illustration of the premix burner in the direction of flow, in particular expressing the course of the perforated plates 31, 32 belonging to the injector system in relation to the inflow planes 33 of the feed channels 27, 28. This course is parallel, the inflow planes 33 also running parallel to the burner axis 26 of the premix burner over the entire burner length. This figure also shows how the injector nozzles 31a, 32a are mounted. There are two possibilities here of guiding the injector nozzles 31a, 32a. On the one hand, the upper illustration shows a completely vertical course of the injector nozzles 32a. On the other hand, the lower illustration shows a different course of the injector nozzles 31a: Here they have an inflow angle which changes continuously in the direction of flow with respect to the burner axis 26. From an initially acute angle in the area of the head stage of the premix burner, this gradually increases until the injector nozzles 31a in the area of the burner end are then approximately perpendicular to the burner axis 26. Which design variant is used depends on the specific operating parameters and other auxiliary measures. Mixed forms of vertical and oblique injection are also possible. In order to maximize the quality of the mixture of the air / flue gas mixture 7 and to strengthen the positional stability of the backflow zone (see FIG. 1), the partial bodies 1, 2 (see FIGS. 1-3) are equipped with guide vanes 50. These deflect the tangentially and largely vertically inflowing air / flue gas mixture 7 in an axial or quasi-axial direction. The inflow angle a, ie the angle of the corresponding guide vane with respect to the burner axis 26, increases from the burner head to the burner outlet, the angularity of these guide vanes 50, of course, being dependent on the respective inflow plane of the injector nozzles 31a, 32a. In the area of the firing outlet, the last-acting guide vane is essentially almost perpendicular to the burner axis 26. Expressed in numbers, the angle increases with vertically acting injector nozzles 31a from initially approximately 40 ° to an angle α _n of approximately 80 °. So that these guide blades 50 can work properly, their number is selected within the length of the premix burner so that the ratio between the distance S of the guide blades to one another and the width H of the tangential air inlet ducts into the interior of the premix burner is approximately 1. This eliminates the disadvantages broken down in the "State of the art" chapter above.

5 and 6 show essentially the same configuration according to FIGS. 3 and 4, the perforated plates 34, 35 with the associated injector nozzles 34a, 35a also parallel to the inflow planes 36 over the entire length of the burner of the feed channels 27, 28 run. Meanwhile, these inflow planes 36 run conically with respect to the burner axis 26 of the premix burner. Of the variable inflow angle of the injector nozzles 34a, 35a in the flow direction also largely corresponds to the configuration according to FIGS. 3 and 4, wherein here the gradual erection of these injector nozzles 34a, 35a into one vertical inflow in the area of the outlet of the premix burner primary opposite the inflow plane 36 of the respective feed channel judges. The arrangement and angular position of the to be sent here, too, but not Guide vanes shown in detail are due to the burner axis 26 corresponding to the specified inflow levels of the air / exhaust gas mixture customized.

Reference list

1, 2

Partial conical body

3, 4

Central axis to 1 resp. 2nd

5, 6

Tangential air intake ducts

7

Combustion air

8th

Cone cavity, interior of the burner

9, 10

Cylindrical starting parts of the burner

11

Fuel nozzle

12th

Fuel, liquid fuel

13.14

Fuel lines

15

Injection openings of the fuel line 13, 14

16

Fuel, gaseous fuel

17th

Combustion chamber

18th

Front panel

19th

Holes in the front panel

20th

Air, mixed air, cooling air

21

Air inlet level

22

Fuel injection level

23

Fuel profile

24th

Backflow zone, backflow bubble

25th

Flame front

26

Main central axis, burner axis

27.28

Feed channels

29

Fresh air

30th

Recirculated flue gas

31.32

Perforated plates

31a, 32a

Injector nozzles

33

Inflow plane of the inlet ducts 27, 28

34.35

Perforated plates

34a, 35a

Injector nozzles

36

Inflow plane of the feed channels 27, 28

50

Guide body, guide vanes

200

Injector system

α

Inflow angle

α _n

Inflow angle

S

Guide blade spacing

H

Tangential air inlet duct

Claims (13)

Burner for operating a unit for generating a hot gas, the burner consisting essentially of at least two hollow, conical, partial bodies nested in the flow direction (1, 2) exists, the central axes (3, 4) of which are offset from one another, that adjacent walls of these partial bodies (1, 2) are tangential Air inlet channels (5, 6) for the inflow of combustion air (7) in form an interior (8) formed by the partial bodies (1, 2), and wherein the burner can be operated with at least one fuel nozzle (11, 15), characterized in that the partial bodies (1, 2) on their inner walls spaced apart and in operative connection with that in the interior (8) inflowing combustion air (7) acting guide body (50). Burner according to Claim 1, characterized in that the guide bodies (50) have a variable flow angle (α, α _n ) in relation to the burner axis (26) in the longitudinal direction of the burner. Burner according to claim 2, characterized in that the flow angle the guide body (50) between 40 ° at the burner head and 80 ° at Burner outlet increases. Burner according to claim 1, characterized in that the ratio between distance (S) of the individual guide bodies (50) to one another and the Width (H) of the tangential air inlet ducts (5, 6) is approximately 1. Burner according to claim 1, characterized in that the guide body (50) have the shape of guide vanes. Burner according to claim 1, characterized in that the fuel nozzle (11) is arranged on the head side and on the burner axis (26). Burner according to claim 1, characterized in that in the area of tangential air inlet channels (5, 6) in the longitudinal extension of the burner Number of spaced apart fuel nozzles (15) are. Burner according to claim 1, characterized in that the flow cross section of the interior (8) formed by the partial bodies (1, 2) in Flow direction increases uniformly. Burner according to claim 1, characterized in that the flow cross section of the interior (8) formed by the partial bodies (1, 2) Diffuser, a diffuser-like course, a confuser, a confuser-like Course forms. Burner according to claim 1, characterized in that the partial body (1, 2) are nested in a spiral. Burner according to claim 1, characterized in that in radial or quasi-radial direction with respect to the air inlet channels (5, 6) supply channels (27, 28), which each have at least one injector system (200) for providing a fresh air (29) and flue gas (30) existing combustion air (7). Burner according to claim 11, characterized in that the injector system (200) associated perforated plates (31, 32; 34, 35) parallel to the respective Inflow plane (33, 36) of the combustion air (7) into the feed channels (27, 28) run that the perforated plates in the area of the inflow planes are provided with injector nozzles (31a, 32a; 34a, 35a), and that the inflow angle of the injector nozzles in the axial direction of the burner perpendicular to the burner axis (26) and / or quasi-vertical stands, and / or is continuously changeable. Burner according to claim 12, characterized in that the flow level the injector nozzles (31a, 32a; 34a, 35a) in the area of the burner head has an acute angle, and that this angle in axial Direction of the perforated plates (31, 32; 34, 35) gradually increases until this Area of the burner outlet approximately perpendicular to the inflow planes (33, 36) of the feed channels (25, 26) and / or to the burner axis (26) of the burner.

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