EP1856442B1 - Premix burner for producing an ignitable fuel/air mixture - Google Patents

Abstract

The invention relates to a premix burner for producing an ignitable fuel/air mixture, comprising a swirl generator, which provides at least two burner shells (1) that complete one another to form a flow body. These burner shells, together, enclose a swirl space that conically enlarges in an axial manner and, in an axial longitudinal extension of the cone, delimit mutually tangential air entry slits (3) via which the combustion supply air arrives in the swirl space, inside of which an axially expanding swirling flow is formed. The premix burner also comprises means (6) for injecting fuel that are provided, at least in areas, along the tangentially running air inlet slits (3). The invention is characterized in that: the means for injecting fuel is provided in the form of a fuel line (6), which is separate from the fuel shell (1), can longitudinally move relative to the burner shell (1), and which is detachably joined in a fixed manner to the burner shell (1) while being perpendicular to the surface of the burner shell (1), and; openings (4) are provided in the burner shell (1), into which fuel injectors (7) lead that are provided along the fuel line (6) and project beyond the peripheral edge of the fuel line (6).

Description

Technical area

The invention relates to a premix burner for producing an ignitable fuel-air mixture, with a swirl generator, which provides at least two supplementing to a flow body burner shells, which together enclose an axially conically widening swirl space and limit each other in the axial longitudinal cone extension mutually tangential air inlet slots through the Combustion air enters the swirl space, in which an axially spreading swirl flow is formed, and with means for injecting fuel, which are provided at least in sections along the tangentially extending air inlet slots.

State of the art

Premix burners of the abovementioned type are known from a large number of published publications, for example, from 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 overlap overlapping 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 is made to ignite.

To generate swirl, the partial cone shells, which overlap with each other, enclose tangential air inlet slots along the burner axis the radially in the bounded by the partial cone shells swirl space air under impression of a longitudinally to the burner axis propagating swirl flow occurs.

The mostly double-walled partial cone shells provide for fuel supply in the region along the air inlet slots at least one inner fuel supply channel, is supplied through each gaseous fuel, which exits through fuel nozzle openings in the region of the air inlet slots. For this purpose, the fuel openings are distributed in the region of the burner shell wall facing the air inlet slot, in order to ensure an effective and as uniform as possible mixing between the gaseous fuel and the inflowing supply air already in the region of the air inlet slot.

In addition to the double-walled design of the swirl compartment narrowing part cone shells and the use of part cone shells is known, which in turn are formed only of single-walled flat materials for air guidance. Such Vormischbrenner see along the leading edge of the Teilkegelschalen each an attachment in the form of a pipeline through which gaseous fuel along the tangential extension of the air inlet slot is fed by appropriately provided in the pipeline holes in the combustion air. For this purpose, the pipeline is firmly connected by way of a soldering or welding connection to the leading edge of the partial cone shell.

Further disclosed EP-A-1070915 a means for injecting fuel, which is formed as a burner shell to the separate line which is passed through a, provided in the burner cup opening and which, has no firm connection with the burner cup.

For reasons of always ensuring operational safety, the supply of gaseous fuel for further feeding along the fuel openings in the region of the air inlet slots usually takes place at gas temperatures in the range between 20 and 30 ° C. On the other hand, due to operational prevailing due to the prevailing in the air inlet slots radiation temperatures temperatures between 300 to 350 ° C. It is obvious that all those partial cone shell surfaces delimiting the air inlet areas have body temperatures in the range of the above radiation temperatures. On the other hand, the partial cone cup portions are cooled immediately around the fuel holes by the cool gas flow. Due to these temperature differences occur in the Area of fuel openings on high thermal gradients, which lead to cracks within the material surrounding the fuel openings. The consequence of this is irreversible structural weakening, which may possibly lead to a total loss of at least the affected partial cone shell. In addition, the risk of local flashbacks in the channel areas of the fuel supply increases in cracked fuel openings, which ultimately also the reliability of such a weakened premix burner is in question.

Presentation of the invention

The invention has for its object a Vormischbrenner for generating a combustible fuel-air mixture, with a swirl generator of at least two complementary to a flow body burner shells, which together enclose an axially widening conically widening swirl space and limit each other in the axial longitudinal extent of the cone tangentially air inlet slots through the Combustion air enters the swirl space in which forms an axially spreading swirl flow, and with means for injecting fuel, which are provided at least partially along the tangential air inlet slots, educate such that the means for injecting fuel along the air inlet slots no thermally induced Cracking experienced operationally.

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 solution, a premix burner according to the features of the preamble of claim 1 is developed in such a way that the means for injecting fuel is formed as a fuel line separate from the burner shell, which is longitudinally movably fixed to the burner shell along the burner shell and perpendicular to the surface of the burner shell. In the burner bowl are Holes provided, open into the fuel injectors, which are provided along the fuel line, which project beyond the peripheral edge of the fuel line.

The invention is based on the idea to carry out the necessary means for injecting gaseous fuel along the air inlet slot means as separate components, preferably as a separate component, and so spatially relative to the burner cup, so that thermal gradients can be avoided within the material. In particular, those components in which the comparatively cool burner gas is guided have to be formed and fastened separately from the burner shells, which are heated to correspondingly high temperatures due to the direct radiation exposure in the area of the swirl space. Component separation eliminates thermal stresses within the burner shells, thereby eliminating material cracks and the associated problems and hazards.

At the same time, provision must be made to connect the means required for fuel supply and fuel feed into the area of the air inlet slots to the burner shells so as to ensure, on the one hand, that the means are reliably attached to the burner shells, but, on the other hand, to move the means relative to the burner bowl are stored to tolerate thermally induced material expansions.

The fuel line provided for supplying fuel to each individual burner shell is designed for this purpose in the form of a conduit tube sealed off on both sides and has a tube length which is adapted to the axial extension of the respective burner shell and does not protrude beyond it. The fuel line associated with each individual burner shell is connected by at least one retaining means on the burner shell surface remote from the swirl space, such that the fuel line is largely fixed to the burner shell surface by clamping force, but is preferably mounted away from the burner shell surface by a separating gap and largely freely movable in the axial direction to the burner shell is stored.

By this storage, it is possible that the fuel line is able to expand independently of the burner shell, so that no thermally induced voltages between the fuel line and burner shell can occur, i. There is complete independence in the thermal expansibility between the fuel line and the burner shell, which is responsible as aerodynamic structure for the flow control within the burner.

From the oriented in the axial extent relative to the burner shell fuel line open so-called fuel injectors that protrude at least partially provided by openings provided within the burner shell or holes. The fuel injectors are formed in a preferred embodiment as each having a hollow channel sleeve members having a maximum the peripheral edge of the fuel line towering elevation, with which they connect flush to the fuel line facing away from the surface of the burner shell. As a result, only a narrow, annular front edge of a fuel injector is exposed to the prevailing within the air inlet slot temperatures, whereby each individual fuel injector is heated only slightly or in a negligible manner. In essence, both the fuel line and the fuel injectors required to inject the gaseous fuel into the air inlet slot remain at the low temperature level imposed by the gaseous fuel stream. Thermal stresses due to occurring thermal gradients are thus almost completely excluded.

Nevertheless, it requires a further attachment of the fuel burner associated with each burner shell, especially since it must be prevented that the fuel line drops during normal burner operation of the respective burner shell. For this purpose, each individual fuel line is provided with a connecting web, via which the fuel line is firmly connected to a component of the premix burner, which is not part of the burner shell. Preferably serves as a suitable support structure for this purpose at the downstream end portion of the swirl generator, all burner shells enclosing form element, that the swirl flow forming within the swirl generator is transferred axially downstream into a combustion chamber or a mixing section provided between combustion chamber and swirl generator in a streamlined manner.

In a particularly advantageous manner, the connecting web is not attached directly to the fuel line extending parallel to the longitudinal extent of the burner shell, the fuel line provides a connecting flange, to which a fuel supply line is fluid-tightly connected and to which also the connecting web is added. The connecting web is optimized in length and shape to the effect that the fuel line is mounted as low vibration with respect to the burner shell, also applies the burner vibrations originating from the burner vibrations as possible not along the connecting web to transfer the fuel line. For this purpose, the cross section of the connecting web is formed along its extension with variably shaped cross-sectional shapes, for example. Elliptical cross-sectional shapes are very well suited for targeted suppression of vibration modes occurring in the burner.

For further description of the inventive concept, reference is made to the exemplary embodiment described in more detail in the figures.

Brief description of the invention

Fig. 1

dreidimensionale Darstellung einer Brennerschale mit lösungsgemäss angebrachter Brennstoffleitung,

Fig. 2

dreidimensionale kranzförmige Anordnung einer Vielzahl von Brennerschalen um eine Einlaufgeometrie eines Vormischbrenners,

Fig. 3

perspektivische Darstellung einer Brennstoffleitung, sowie

Fig. 4

Detaildarstellung einer in einer Brennerschale eingebrachten Brennstofföffnung.

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 drawing. Show it:

Fig. 1

three-dimensional representation of a burner shell with a fuel pipe attached in accordance with the solution,

Fig. 2

three-dimensional annular arrangement of a plurality of burner shells around an inlet geometry of a premix burner,

Fig. 3

perspective view of a fuel line, as well

Fig. 4

Detail of a fuel port introduced in a burner bowl.

Ways to carry out the invention, industrial usability

In FIG. 1 is a three-dimensional view of a single burner shell 1 is shown, the upper side facing away from the swirl space facing the viewer visibly.

To facilitate understanding of the spatial arrangement and functioning of the FIG. 1 burner shell is also on the in FIG. 2 shown swirl generator a Vormischbrenners referenced, the eight individual burner shells 1 provides, which are arranged in a ring shape around a mold element 2 and each internally enclosed in each case a conically expanding swirl space. For reasons of clarity, a retaining ring to be provided for the stability of the burner shells 1, which centrally supports the upper ends of the burner shells in the illustration, is not shown, especially as it does not depend on this to explain the measure according to the solution.

For technical understanding of in FIG. 2 illustrated burner shell assembly is noted that each two immediately adjacent arranged burner shells 1 together include an air inlet slot 3 through which flows in the radial flow direction in each case a supply air flow L in the limited by the burner shells 1 inside swirl space. The forming within the swirl space swirl flow occurs from the in FIG. 2 shown swirl generator down (see arrow) off. To form an ignitable fuel-air mixture, gaseous fuel in the region of the air inlet slot 3 of the inflowing combustion air L is added in a manner known per se. This is done by located within the burner shells 1 openings 4, which are arranged in each axial extent of each burner shell, preferably along a straight line.

The fuel supply takes place at each individual burner shell via a fuel supply line 5 (see FIG. 1 and 2 ), which is connected to a tubular fuel line 6. The tube-like fuel line 6 is formed in each case closed at its two pipe ends and arranged as a separate component relative to the burner shell 1. As further below, in particular with reference to the Figures 3 and 4 shows the pipe 6 sleeve-like design fuel injectors 7 facing the burner shell 1 facing at least partially open into or through the provided in the burner shell 1 openings 4.

For fastening the tube-like fuel line 6 to the burner shell 1, a holding means 8 is provided, which supports the fuel line 6 radially, i. perpendicular to the surface of the burner shell 1 clamped tensioned and ensures that the projecting into the openings 4 within the burner shell 1 fuel injectors 7 remain securely in the openings and can not "slip out". On the other hand, the retaining means 8 formed as a retaining clip offers the possibility that the fuel conduit 6 can be moved along its longitudinal axis, i. axially relative to the burner shell, at least slightly able to perform relative movements, in order to prevent in this way any distortion phenomena and clamping between the fuel line 6 and the burner shell 1 due to different thermal expansion behavior.

The holding means 8 designed as a retaining clip has a shape adapted to the outer contour of the pipeline 6, in the case of a cylinder-shaped fuel line 6 the retaining means is U-shaped and connected to both U-legs at the top of the burner shell 1. The connection between the holding means 8 and the burner shell 1 is carried out either in the context of a fixed connection, for example solder or welded connection or by means of a releasably fixed connection, through which a simplified assembly and disassembly of the burner components is possible.

For further attachment, the fuel line 6 via a connecting web 9 fixed to the inlet geometry of the mold element 2 (see FIG. 2 ) connected. The connecting web 9 leads to a fixedly connected to the fuel line 6 connecting flange 10 which establishes a gas-tight connection between the fuel line 6 and supply line 5.

In FIG. 3 is a schematic perspective view of the fuel line 6 shown as a separate component. The tube-shaped fuel line 6, which is closed gas-tight at both opposite end regions 11, 12, has openings 13 in a linear arrangement along its axial extension, in which so-called fuel injectors 7 are integrated.

The sleeve-like fuel injectors 7 each protrude beyond the peripheral edge of the tubular fuel line 6, so that they in the in FIG. 3 not shown openings within the burner shell 1 at least partially open. In the illustrated embodiment in FIG. 3 two separate fuel supply lines 5, 5 'are provided, via which gaseous fuel from two different fuel supply circuits of the fuel line 6 is supplied. In principle, however, it is possible to connect the fuel line 6 with only a single supply line. At the Anflanschstück 10 directly connected to the fuel line, the connecting web 9 is attached, which provides a mounting foot 14 to which the separate unit is firmly attached to the inlet geometry of the mold element 2, preferably by means of a soldered or welded connection.

FIG. 4 shows a partial cross-sectional view through the fuel line 6 in the region of a fuel injector 7, which opens into the opening 4 of a burner shell 1. The fuel injector 7 is sleeve-like and has an inner hollow channel 15, injected by the gaseous fuel from the interior of the fuel line 6 in the bounded by two adjacent burner shells air inlet gap 3. To ensure a largely thermal decoupling between the burner shell 1 and the fuel line 6 is the Peripheral edge of the fuel line 6 from the fuel line 6 facing top of the burner shell 1 spaced. Either this can be done by providing an air gap between the two components, which is ensured by means not shown spacers between the fuel line 6 and the burner shell 1, or by means of a suitably provided thermally or poorly conductive intermediate layer.

To an axial relative mobility between the fuel line 6 and burner shell 1 according to arrow in FIG. 4 To be able to ensure that provided within the burner shell 1 openings are formed with a slight excess over the diameter of the fuel injectors, so that sets a clear air gap between the outer peripheral edge of the respective fuel injector 7 and the opening 4. In a preferred embodiment, the openings 4 introduced within the burner shell 1 are designed as elongated holes oriented in the axial extension of the burner shell, in order in particular to allow the greatest possible possibility of relative longitudinal expansion for the area of the fuel line 6 located furthest away from the connecting web 9. Likewise, the partial cross-sectional view according to FIG. 4 can be taken that the formed as a sleeve element fuel injector 7 is connected via at least one intermediate element 16 with the pipe wall to keep as low as possible over the sleeve member of the fuel injector 14 to the fuel line 6 acting heating.

Due to the separate design of the fuel line 6 and its storage described above the burner shell 1 can be largely excluded any thermal stresses between the two components and in particular the associated risk of possible cracking in the material of the burner shell in the fuel holes are avoided.

LIST OF REFERENCE NUMBERS

1

burner shell

2

forming element

3

Air inlet gap

4

Opening inside the burner bowl

5, 5 '

supply line

6

fuel line

7

fuel injector

8th

holding means

9

connecting web

10

connecting flange

11.12

End portions of the fuel line 6

13

Opening within the fuel line

14

mounting foot

15

hollow channel

16

connecting piece

Claims (7)

1. Premixing burner for generating an ignitable fuel/air mixture, with a swirl generator which provides at least two burner shells (1) which complement one another to form a throughflow body and which jointly enclose an axially conically widening swirl space and delimit with respect to one another, in the axial longitudinal extent of the cone, tangential air inlet slits (3) through which combustion supply air passes into the swirl space in which an axially propagating swirl flow is formed, and with means (6) for the injection of fuel, which are provided at least partially along the tangentially running air inlet slits (3), characterized in that the means for the injection of fuel is designed as a fuel line (6) which is separate from the burner shell (1) and which is firmly attached to the burner shell (1) so as to be longitudinally movable with respect to the burner shell (1) and so as to be releasable perpendicularly to the surface of the burner shell (1), and in that, in the burner shell (1), orifices (4) are provided, into which issue fuel injectors (7) which are provided along the fuel line (6) and project beyond the circumferential edge of the fuel line (6).
2. Premixing burner according to Claim 1, characterized in that, along the burner shell (1), a holding means (8) is provided, which is connected firmly or releasably firmly to the burner shell (1) and which fixes the fuel line (6), while applying a prestress directed perpendicularly to a surface of the burner shell (1) which faces the fuel line (6).
3. Premixing burner according to Claim 1 or 2, characterized in that, between that surface of the burner shell (1) which faces the fuel line (6) and the fuel line (6), an air gap is provided, which is ensured by means of spacer elements between the surface of the burner shell (1) and the circumferential edge of the fuel line (6).
4. Premixing burner according to one of Claims 1 to 3, characterized in that at least some of the orifices (4) in the burner shell (1) are designed in the form of long holes, in each case with a largest hole diameter which is oriented in the longitudinal direction of the fuel line (6).
5. Premixing burner according to one of Claims 1 to 4, characterized in that the fuel line (6) has a connecting web (9), via which the fuel line (6) is firmly connected to a component of the premixing burner which is not part of a burner shell (1).
6. Premixing burner according to Claim 5, characterized in that, at the downstream end region of the swirl generator, a molded element (2) surrounding the burner shells (1) is provided, to which the connecting web (9) of each fuel line (6) is fastened.
7. Premixing burner according to one of Claims 1 to 6, characterized in that the fuel injectors (7) are designed in the form of sleeve elements which have in each case a hollow duct (15) and which have at most an elevation which projects beyond the circumferential edge of the fuel line (6) and by means of which they are joined, flush, to that surface of the burner shell (1) which faces away from the fuel line (6).

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