EP1714081B1 - Premixing burner arrangement for operating a burner chamber and method for operating a burner chamber - Google Patents

Abstract

A premix burner is disclosed for operating a combustion chamber with a gaseous and/or liquid fuel, having a swirl generator for inducing a swirl flow in an incoming combustion air flow and a device for injecting fuel into the swirl flow, the swirl generator having at least two cone shell segments which fit together to form a flow body and together enclose a conically formed swirl space with a cone angle gamma and air inlet slits directed tangentially to the length of the cone. At least at the downstream end region of the swirl generator, a shaped element enclosing the cone shell segments with an inside wall facing the cone shell segments is provided, and that the cone shell segments end in the inside wall in a flush manner while maintaining their shape.

Description

Technical area

The invention relates to a premix burner for operating a combustion chamber with a gaseous and / or liquid fuel with a swirl generator for a combustion air flow to form a swirl flow and means for injecting fuel into the swirl flow, wherein the swirl generator at least two complementary to a flow body cone shells which together form a cone-shaped swirl space with a cone angle γ and tangential air inlet slots in the longitudinal direction of the cone.

State of the art

Premix burners of the aforementioned type are known from a variety of prepublished publications, such as. From the EP 0 210 462 A1 as well as the EP 0 321 809 B1 , to name just a few. Premix burners of this type is based on the general operating principle, within a mostly designed as a conical swirl generator, which provides at least two with corresponding mutual overlap Teilkegelschalen to produce a consisting of a fuel-air mixture swirl flow, which within a downstream of the premix burner combustion chamber under training a spatially stable as possible premix flame brought to ignition becomes. Here, the spatial position of the premix flame is determined by the aerodynamic behavior of the swirl flow whose swirl increases with increasing propagation along the burner axis, thus becomes unstable and ultimately bursts through an unsteady cross-sectional transition between the burner and combustion chamber in an annular swirling flow to form a backflow zone, in whose , in the flow direction front area, the premix flame is formed.

Of particular importance is the aerodynamic stability of the forming Rückströmzone, but highly sensitive to the design, shape and size of the swirl generator depends. If, for example, it is not possible to spatially stabilize the upstream front of the forming backflow zone in the direction of flow, then thermoacoustic oscillations or pulsations within the combustion system occur, which considerably affect the overall combustion and the heat release.

Bearing this in mind, the previously known and in use Vormischbrennersysteme be limited to sizes whose maximum burner diameter at the burner outlet is only 180 mm. Moreover, such premix burners have a relatively sharp, i. small cone angle of less than or equal to 18 °, so that the burner length in relation to the down-turned burner diameter rather large, but for assembly and maintenance purposes is still quite manageable.

However, if large combustion chambers are to be fired, so-called multiple burner arrangements, which provide for the use of the above premix burners, have hitherto been used. Such multiple burner arrangements go, for example, from DE 42 23 828 A1 or the DE 44 12 315 A1 out. In order to operate such multiple burner arrangements, which are suitable, for example, for firing a silo combustion chamber, a sophisticated arrangement of the plurality of master or pilot burners serving premix burners, in order ultimately to operate the combustion chamber in the entire load range with the lowest possible emission levels.

However, there is a desire to reduce the complexity and thus the number of individual premix burners that are required for firing large-sized combustion chambers, without having to accept quality losses in the combustion process itself. Moreover, in view of the ever stricter environmental standards with a view to reducing emissions, it is necessary to replace the diffusion single burners currently in operation, which are primarily used to fire large silo combing chambers, with more modern, environmentally sound burner systems. In particular with regard to the avoidance of high conversion and new procurement costs, it is desirable to provide premix burners of the largest possible size in order, for example, to be able to continue the operation of such large-sized silo combustion chambers with only one single premix burner.

Theoretical considerations as well as experiments have shown that a simple scaling, for example, one of the EP 0321 809 B1 known double cone burner is not leading the target, especially, as already mentioned above, the burner length would increase disproportionately. In addition, the width of the burner inlet axis tangentially extending air inlet slots, flows through the combustion air to generate the desired swirl flow in the swirl generator, would also increase proportionally, so that a good mixing of fuel and combustion air supply can not be guaranteed in sufficient quality.

Another very important and at the same time critical aspect in a desired increase or increase in performance of the previously known Vormischbrennersysteme relates to the downstream end of the swirl chamber of the swirl generator enclosing Teilkegelschalen, in the example of the in the EP 0321 809 B1 described double cone burner in axially directed obstructions end. These obstructions contribute to the formation of unwanted separation vortices, which, as coherent vortex structures, lead to combustion instabilities and, associated therewith, to thermoacoustic oscillations or pulsations.

Also Vormischbrenneranordnungen are known (eg US 5,588,826 and WO-A-00/39503 ), which, in contrast to the premix burner described above, have an interposed transition geometry between the swirl generator and the combustion chamber, for example in the form of a hollow cylindrical mixing tube. However, such transition geometries are extremely aerodynamically sensitive, since flow control solutions in this zone can lead to flashback or auto-ignition. Likewise, such transition geometries contribute significantly to the manufacturing costs due to their complex production.

Presentation of the invention

The invention has the object of developing a premix burner according to the features of the preamble of claim 1 such that despite enlarging the burner dimensions, the burner properties optimized in previously known premix burners should remain virtually unchanged. Thus, it is necessary to increase the burner size of previously known premix burner systems in order to reduce the number of burners in multiple burner arrangements, as described above, as well as the associated system costs. Likewise, it should be possible with the larger-sized premix burner systems to replace previously known diffusion single burner, as used for example for firing silo combustion chambers in use, by a single premix burner.

The solution of the problem underlying the invention is specified in claim 1. The concept of the invention advantageously further features are the subject of the dependent claims and the description in particular with reference to the exemplary embodiments.

According to the invention, a premix burner according to the preamble of claim 1 is developed such that at least at the downstream end region of the swirl generator, a form element enclosing the partial cone shells with a Part cone shells facing the inner wall is provided, and that the Teilkegelschalen terminate flush in the inner wall flush.

To make the premix burner as compact as possible, i. To be able to realize with the shortest possible burner length, cone angles of 20 ° and larger are used, under which the partial cone shells surround the swirl space conically widening. For example, burners with a burner diameter in the exit region of, for example, greater than 500 mm, which have a burner length well below one meter, can be made possible. To ensure a good mixing of the fuel air mixture within the swirl generator, it is also advantageous to increase the number of partial cone shells and the associated number of air inlet slots, thus achieving the smallest possible slot width per air inlet slot.

A variety of theoretical considerations as well as experimentally performed experiments to increase the previously known design of premix burners, which usually have a maximum burner outlet side burner diameter of 180 mm, led to the realization that the downstream end structure of the partial cone shells a significant impact on the stability of forming Vormischbrennerflamme has, in particular in an effort to form the premix burner as large as possible.

It is thus evident that in most cases the premix burners in use transition the end regions of the partial cone shells in the flow direction into a hollow cylindrical flow channel, which is adjoined either directly by the combustion chamber or an additional mixing section in the form of a mixing tube. To avoid the subsequent in the flow direction directly to the partial cone shells separation vortices has been recognized according to the invention that the swirl flow is able to spread immediately after exiting the swirl generator largely without instability of the swirl flow, if the individual Teilkegelschalen form-retaining with the inner wall of the adjoining the swirl generator flow channel nestle. The term "shape-retaining" in the context of the invention means that the partially cone-shaped shape of the subcone shells in the area of coming into contact with the inner wall of the part cone shells enclosing the form element remains unchanged, as if the Teilkegelschalen penetrate the mold element radially outward unhindered.

To form a downstream of the part cone shells subsequent flow channel is used in the other the inner wall of the mold element. Depending on the shape and size of the mold element this serves further as a mixing tube or as a joining element, in the sense of a flange piece on which the swirl generator with an in Flow direction downstream combustion chamber, such as a silo combustion chamber, or another channel structure is connectable.

Brief description of the invention

Fig. 1 + 2

perspektivische Darstellung eines Vormischbrenners mit einem zylinderförmig ausgebildeten Formelement,

Fig. 3 + 4

perspektivische Darstellung eines Vormischbrenners mit einem kegelstumpfförmig ausgebildeten Formelement,

Fig. 5

Schnittdarstellung durch einen Vormischbrenner mit einem kegelstumpfförmig ausgebildeten Formelement sowie

Fig. 6 + 7

perspektivische Darstellung eines Vormischbrenners mit einem einen trichterförmig ausgebildeten Eintrittsbereich aufweisenden Formelement.

The invention will now be described by way of example without limitation of the general inventive idea by means of embodiments with reference to the drawings. Show it:

Fig. 1 + 2

perspective view of a premix burner with a cylindrical shaped element,

Fig. 3 + 4

perspective view of a premix burner with a frusto-conical shaped element,

Fig. 5

Sectional view through a premix burner with a frusto-conical shaped element and

Fig. 6 + 7

perspective view of a premix burner with a funnel-shaped inlet region having molding element.

Ways to carry out the invention, industrial usability

In Fig.1 is a perspective view of a premix burner, viewed from the downstream side into the spanned by a plurality of sub-cone shells 1 swirl space of a swirl generator 2 inside. Fig. 2 shows the same premix burner, but from a different angle, namely from the outside to the swirl generator 2, which is spanned in the illustrated embodiment of eight partial cone shells 1. The other external guides with respect to the in the Fig. 1 and 2 illustrated embodiment are uniform, so that in the following no distinction between Fig. 1 and FIG.

The premix burner shown has a central, in the form of a receiving sleeve receiving unit 3, which is provided for insertion and holding a central Brennstoffzuführeinheit, eg. In the form of a fuel nozzle for liquid fuel or burning lance for a pilot flame (not shown). The partial cone shells 1 connected to the receiving unit 3 at their upstream ends enclose mutually air inlet slots 4 and are set in relation to a burner axis A running centrally through the premix burner such that they delimit a swirl space widening conically in the direction of flow at a cone angle γ. Each individual cone shell 1 also has, depending on the type of fuel, at least one fuel supply line 5, via which fuel can be added to the combustion supply air stream passing through the air inlet slots 2.

The individual part cone shells 1 open with their downstream end form-retaining edge on an inner wall 6 of a part cone shells 1, cylindrically shaped mold element 7. The individual cone shells 1 are connected to the inner wall 6 of the mold element 7 along a section line 8, extending through a virtual penetration each individual sub-cone shell 1 with the inner wall 6 of the cylindrical shaped element 7 results. In this way, the swirl flow formed in the interior of the swirl generator 2 undergoes no disturbance after overflow of the individual partial cone shells 1.

Upstream of the mold element 7, for purposes of an improved supply air flow through the air inlet slots 4 of the swirl generator 2, a second mold element 9 is provided, which is also hollow cylindrical and has a larger inner diameter than the first mold elements 7. The inner diameter transition between the mold elements 7 and 9 takes place via a discontinuous stage 10, to the rest of the fuel feeders 5 each individual cone bowl 1 adjacent.

The downstream contour of the mold element 7 is cylindrical and offers the possibility of a structurally simple connection, for example, with a premix burner shown in the flow direction to parent combustion chamber (not shown).

In the 3 and 4 is a perspective view of another embodiment of an inventively designed Vormischbrenners shown in which, in contrast to the embodiment, in the Fig. 1 and 2 is shown, the region of the mold element 7 is formed as in the flow direction conically tapered truncated cone section. In order to avoid repetition, the description of the previously introduced reference numerals is omitted. That in the 3 and 4 illustrated embodiment, in the region of the mold element 7 a hatched in the perspective views shown inner wall 6, to which the downstream ends of the part cone shells 1 adjoin the former. On the inner wall 6 of the mold element 7 is adjacent to a hollow cylinder shaped shaped element 11 downstream, which serves as a coupling or flange piece for a subsequent combustion chamber. By contrast with the pitch cone shells 1 employed inner wall 6 are the section lines 8 of the subcone shells 1, with which they adjoin the inner wall 6 smaller or shorter in the flow direction than in the case of the preceding embodiment, in which the cone shells along a coaxial with the burner axis directed cylindrical Adjoin the inner wall.

A diagrammatic cross-sectional view of the in the 3 and 4 shown embodiment is in Fig. 5 seen. Clearly recognizable is the shape-retaining abutment of each individual cone shells 1 to the inner wall 6 of the cone-shaped in the flow direction conically tapered mold element 7, which merges in the flow direction in a straight-cylindrical region 11.

In the FIGS. 6 and 7 is a further embodiment of a premix burner shown with a mold element 7, which provides an upstream region, the so-called inflow region 12, which has a funnel-shaped inner wall 6 tapering in the flow direction. The curvature of the inner wall 6 in this inflow region 12 corresponds approximately to the contour of a quarter ellipse. In the flow direction of the inflow region 12, a flow region 12 'with a substantially constant flow cross section adjoins the mold element 7, to which end an inlet flange of a combustion chamber can finally be attached (not shown). As in the variants described above, the subcone shells 1 of the swirl generator 2 run flush with their Teilkegelschalenform in the adjacent inner wall 6 of the mold element 7, as if the Teilkegelschalen penetrate the inner wall 6 unhindered, but the Teilkegelschalen 1 close each on the section lines 8 the inner wall 6 from. In the case of the inflow region 12 designed as a quarter ellipse, the downstream end regions of the partial cone shells 1 conform to the ellipse curvature of the inner wall 6 in this region 12. On the meaning of the already introduced reference numerals, which in the FIGS. 6 and 7 are additionally provided, reference is made to the preceding figures.

The connection according to the invention of each individual cone shell with its downstream end region in form-retaining manner with an inner wall of a molding element surrounding the partial cone shells leads to the least irritation of the swirling flow passing through the partial cone shells. In contrast to the previously known Vormischbrennern no Versperrwirkungen in axial Direction through the burner axis with the inventive, shape-retaining leakage of the partial cone shells connected to the corresponding inner wall.

LIST OF REFERENCE NUMBERS

1

Cone shell

2

swirl generator

3

recording unit

4

Air inlet slots

5

Fuel supply line

6

inner wall

7

forming element

8th

cutting plane

9

forming element

10

step

11

Hohtzytinderförmig formed molding

12

inflow

Claims (10)

1. Premix burner for operating a combustion chamber with a gaseous and/or liquid fuel, having a swirl generator (2) for inducing a swirl flow in an incoming combustion air flow and means (5) for injecting fuel into the swirl flow, the swirl generator (2) having at least two cone shell segments (1) which fit together to form a flow body and together enclose a conically formed swirl space with a cone angle γ and air inlet slits (4) directed tangentially to the length of the cone, wherein, at least at the downstream end region of the swirl generator (2), a shaped element (7) enclosing the cone shell segments (1) with an inside wall (6) facing the cone shell segments (1) is provided, and wherein the cone shell segments (1) end in the inside wall (6) in a flush manner while maintaining their shape; characterized in that the cone angle γ is greater than or equal to 20° and the swirl generator (2) has a downstream burner diameter of greater than 180 mm.
2. Premix burner according to Claim 1, characterized in that the shaped element (7) encloses the cone shell segments (1) at their downstream end region in an annular manner in such a way that the inside wall (6) of the shaped element (7) is connected in each case to the cone shell segment (1) by means of a line of intersection (8) through the respective cone shell segment (1), along which the cone shell segment (1) virtually penetrates the inside wall (6) while maintaining its shape.
3. Premix burner according to Claim 1 or 2, characterized in that the inside wall (6) is frustoconically formed and has a contour tapering conically in the direction of flow.
4. Premix burner according to Claim 1 or 2, characterized in that the inside wall (6) has adjoining the swirl generator (2) directly downstream an inflow region (12) in which the inside wall (6) is formed tapering in a funnel-shaped manner in the direction of flow.
5. Premix burner according to Claim 4, characterized in that the inside wall (6) has in the inflow region (12) a curvature contour formed in longitudinal section as a quarter ellipse.
6. Premix burner according to Claim 4 or 5, characterized in that downstream of the inflow region (12) the inside wall (6) goes over into a flow portion (12') which has a flow cross section remaining the same in the direction of flow.
7. Premix burner according to Claim 1 or 2, characterized in that the inside wall (6) is cylindrically formed.
8. Premix burner according to Claim 3 or 7, characterized in that the first shaped element (7) is adjoined in the direction of flow by a further shaped element (11), with a further inside wall, which axially has a constant flow cross section.
9. Premix burner according to one of Claims 1 to 8, characterized in that at least four, preferably eight, cone shell segments (1) are provided to form the swirl space.
10. Use of the premix burner according to one of Claims 1 to 9, for firing a silo combustion chamber.

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