EP0903540B1 - Burner for operating a heat generator - Google Patents

Description

Technical field

The invention relates to a burner for the operation of a heat generator according to Preamble of claim 1.

State of the art

From EP-A2-0 780 630 and from EP-0 780 629 A2 a burner has become known, which on the inflow side a swirl generator, the flow formed therein seamlessly into one Mixing section is transferred. This is done using one at the beginning of the mixing section flow geometry formed for this purpose, which consists of transition channels exists, which is sectoral, according to the number of acting partial bodies of the swirl generator, capture the end face of the mixing section and in the direction of flow twist. The outflow side of these transition channels has the Mixing section on a number of filming holes, which increase the Ensure flow velocity along the pipe wall. Then follows a combustion chamber, the transition between the mixing section and the Combustion chamber is formed by a cross-sectional jump, in the plane of which forms a backflow zone or backflow bubble.

The swirl strength in the swirl generator is selected so that the bursting of the Vortex not within the mixing section, but further downstream, as above executed in the area of the cross-sectional jump. The length of the mixing section is like this dimensioned to ensure sufficient mix quality for all types of fuel is.

Although this burner compared to those from the previous state the technology a significant improvement in terms of strengthening flame stability, lower pollutant emissions, lower pulsations, complete burnout, large operating range, good cross-ignition between the different Burner, compact design, improved mixing, etc., it shows that a further strengthening of flame stability as well as an improved adaptation the flame to the given combustion chamber geometry for a smooth Operation at the highest level in the premix combustion of the newer ones Generation has been needed, especially when it comes to pulsations to eliminate.

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 of the type mentioned To propose kind of precautions which strengthen the flame stability and an adaptation of the flame to the given combustion chamber geometry effect without diminishing in any way the other advantages of this burner.

For this purpose, the one acting on the head and the swirl generator of the burner belonging fuel nozzle, which is preferably on the axis of the swirl generator or the burner and which is usually with a liquid Fuel is fed, surrounded by an annular spaced jacket, in which holes are made in the circumferential direction, through which a Air volume flows around the fuel nozzle. In active connection with these Holes act additional injectors, which are preferably with a gaseous Fuel operated. A small amount of fuel is generated by this Injectors injected into the air volume for flushing around the fuel nozzle, in such a way that the center of the burner flow, which is important for the stability of the flame, always is supplied to the right extent. This ensures that there is a uniform Fuel concentration over the flow cross section of the burner, which lead to suppression of combustion chamber vibrations. This even Fuel concentration across the flow cross-section is particularly important noticeable on the burner axis, where experience has shown it to be uneven Fuel enrichment the vibrations in the flame front arise which lead to pulsations. In addition, with the suppression of Combustion chamber vibrations significantly expand the operating range of the burner, since there is no longer any fear of instability of the flame, which leads to deterioration the deletion limit.

Another advantage of the invention is the fact that the purge air through the above Openings in the area of the fuel nozzle wetting the inner wall of the conical swirl generator prevented by the injected liquid fuel.

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

Exemplary embodiments of the invention are described below with reference to the drawings explained in more detail. All of which are insignificant for the immediate understanding of the invention Features have been left out. The same elements are in the different Figures with the same reference numerals. The flow direction of the media is indicated with arrows.

Brief description of the drawings

Fig. 1

einen als Vormischbrenner ausgelegten Brenner mit einer Mischstrecke stromab eines Drallerzeugers,

Fig. 2

eine schematische darstellung des Brenners gemäss Fig. 1 mit Disposition der zusätzlichen Brennstoff-Injektoren,

Fig. 3

einen aus mehreren Schalen bestehenden Drallerzeuger in perspektivischer Darstellung, entsprechend aufgeschnitten,

Fig. 4

einen Querschnitt durch einen zweischaligen Drallerzeuger,

Fig. 5

einen Querschnitt durch einen vierschaligen Drallerzeuger,

Fig. 6

eine Ansicht durch einen Drallerzeuger, dessen Schalen schaufelförmig profiliert sind,

Fig. 7

eine Ausgestaltung der Uebergangsgeometrie zwischen Drallerzeuger und Mischstrecke und

Fig. 8

eine Abrisskante zur räumlichen Stabilisierung der Rückströmzone.

It shows:

Fig. 1

a burner designed as a premix burner with a mixing section downstream of a swirl generator,

Fig. 2

2 shows a schematic representation of the burner according to FIG. 1 with disposition of the additional fuel injectors,

Fig. 3

a swirl generator consisting of several shells in a perspective view, cut open accordingly,

Fig. 4

a cross section through a double-shell swirl generator,

Fig. 5

a cross section through a four-shell swirl generator,

Fig. 6

2 shows a view through a swirl generator, the shells of which are profiled in a shovel shape,

Fig. 7

an embodiment of the transition geometry between swirl generator and mixing section and

Fig. 8

a tear-off edge for spatial stabilization of the backflow zone.

WAYS OF IMPLEMENTING THE INVENTION, INDUSTRIAL APPLICABILITY

Fig. 1 shows the overall structure of a burner. Initially, a swirl generator is 100 effective, the design of which is shown in more detail in the following FIGS. 3-6 and is described. This swirl generator 100 is a conical one Formation that is tangential multiple times from a tangentially flowing combustion air flow 115 is applied. The current that forms here is based on a transition geometry provided downstream of the swirl generator 100 transitioned seamlessly into a transition piece 200 such that there are none Detachment areas can occur. The configuration of this transition geometry is described in more detail in Fig. 6. This transition piece 200 is on the outflow side the transition geometry extended by a mixing tube 20, both Parts form the actual mixing section 220. Of course, the mixing section 220 consist of a single piece, i.e. then that the transition piece 200 and the mixing tube 20 into a single continuous structure merge, maintaining the characteristics of each part. Become Transition piece 200 and mixing tube 20 created from two parts, so these are connected by a bushing ring 10, the same bushing ring 10 on the head side serves as anchoring surface for the swirl generator 100. Such a bushing ring 10 also has the advantage that different mixing tubes are used can. The actual combustion chamber is located on the outflow side of the mixing tube 20 30, which is only symbolized here by a flame tube. The Mixing section 220 largely fulfills the task that is downstream of the swirl generator 100 a defined route is provided, in which a perfect premix of different types of fuel can be achieved. This mixing section, so ostensibly the mixing tube 20, furthermore enables lossless flow guidance, so that it is also in operative connection with the transition geometry cannot initially form a backflow zone or backflow bubble, which means that Length of the mixing section 220 influences the quality of the mixture for all types of fuel can be exercised. This mixing section 220 has yet another property, which is that the axial velocity profile is in it itself has a pronounced maximum on the axis, so that the Flame from the combustion chamber is not possible. However, it is correct that at in such a configuration, this axial velocity drops towards the wall. Around To prevent re-ignition in this area, the mixing tube 20 in Flow and circumferential direction with a number of regular or irregular distributed holes 21 of different cross-sections and directions, through which an amount of air flows into the interior of the mixing tube 20, and along the wall in the sense of a filming an increase in the flow rate induce. These holes 21 can also be designed in such a way that the inner wall of the mixing tube 20 at least additionally an effusion cooling established. Another possibility is to increase the speed of the mixture To achieve within the mixing tube 20 is that Flow cross-section on the outflow side of the transition channels 201, which already have the called transition geometry form, undergoes a narrowing, whereby the entire speed level within the mixing tube 20 is raised. In In the figure, these bores 21 run at an acute angle with respect to the Burner axis 60. Furthermore, the outlet corresponds to the transition channels 201 the narrowest flow cross-section of the mixing tube 20. The transition channels mentioned 201 accordingly bridge the respective cross-sectional difference, without negatively influencing the flow formed. If the chosen one Precautions when guiding the pipe flow 40 along the mixing pipe 20 causes intolerable pressure loss, this can be remedied, by a diffuser not shown in the figure at the end of this mixing tube is provided. A combustion chamber then closes at the end of the mixing tube 20 30 on, with a through a Burner front 70 formed cross-sectional jump is present. Only here does one form central flame front with a backflow zone 50 which is opposite the Flame front has the properties of a disembodied flame holder. forms there is a flow within this cross-sectional jump during operation Edge zone, in which by the prevailing negative pressure Vortex detachments arise, this leads to an increased ring stabilization of the Backflow zone 50. The combustion chamber 30 has a number of openings on the end face 31 through which an amount of air flows directly into the cross-sectional jump, and the other bottom there contributes to the ring stabilization of the backflow zone 50 is strengthened. In addition, it should not go unmentioned that the generation of a stable Backflow zone 50 also requires a sufficiently high number of swirl in a tube. If this is initially undesirable, stable backflow zones can be created by supplying small, highly swirled air flows at the end of the pipe, for example through tangential openings. Here one assumes that the amount of air required for this is about 5-20% of the total amount of air. As for the design of the burner front 70 at the end of the mixing tube 20 for stabilization Regarding the backflow zone or backflow bladder 50, reference is made to the description referenced in Fig. 8.

FIG. 2 shows a schematic view of the burner according to FIG. 1, with particular reference being made to the flushing of a centrally arranged fuel nozzle 103 and to the effect of fuel injectors 170. The mode of operation of the remaining main components of the burner, namely swirl generator 100 and transition piece 200, are described in more detail in the following figures.
The fuel nozzle 103 is encased with a spaced ring 190, in which a number of bores 161 arranged in the circumferential direction are laid, through which a quantity of air 160 flows into an annular chamber 180 and carries out the purging of the fuel lance there. These bores 161 are made obliquely forward so that an appropriate axial component is created on the burner axis 60. In operative connection with these bores 161, additional fuel injectors 170 are provided, which enter a certain amount, preferably a gaseous fuel, into the respective air amount 160 in such a way that a uniform fuel concentration 150 is established in the mixing tube 20 over the flow cross-section, as shown in FIG Figure symbolizes. It is precisely this uniform fuel concentration 150, in particular the strong concentration on the burner axis 60, that the flame front is stabilized at the outlet of the burner, thus avoiding combustion chamber pulsations.

In order to better understand the structure of the swirl generator 100, it is advantageous to if at least FIG. 4 is used at the same time as FIG. 3. The following will in the description of Fig. 3 referred to the other figures as needed.

The first part of the burner according to FIG. 1 forms the swirl generator shown in FIG. 3 100. This consists of two hollow conical partial bodies 101, 102 which are nested staggered. The number of conical part bodies can of course be greater than two, as shown in Figures 5 and 6; this depends on, as will be explained in more detail below the operating mode of the entire burner. It is with certain operating constellations not excluded, a swirl generator consisting of a single spiral provided. The offset of the respective central axis or longitudinal symmetry axes 101b, 102b (see FIG. 4) of the conical partial bodies 101, 102 to one another creates one on each of the neighboring walls in a mirror-image arrangement tangential channel, i.e. an air inlet slot 119, 120 (see FIG. 4) through which the combustion air 115 in the interior of the swirl generator 100, i.e. in the cone cavity 114 of it flows. The conical shape of the partial bodies 101, 102 shown in Flow direction has a certain fixed angle. Of course, ever after operational use, the partial bodies 101, 102 can increase in the direction of flow or have decreasing cone inclination, similar to a trumpet resp. Tulip. The last two forms are not included in the drawing as they are for the expert can be easily understood. The two conical partial bodies 101, 102 each have a cylindrical annular starting part 101a. In the area this cylindrical initial part is the fuel nozzle already mentioned in FIG. 2 103 housed, which preferably with a liquid fuel 112 is operated. The injection 104 of this fuel 112 coincides with that narrowest cross section of the conical cavity formed by the conical partial bodies 101, 102 114 together. The injection capacity and the type of this fuel nozzle 103 depends on the specified parameters of the respective burner. The tapered partial bodies 101, 102 furthermore each have a fuel line 108, 109, which are arranged along the tangential air inlet slots 119, 120 and are provided with injection openings 117, through which preferably a gaseous fuel 113 is injected into the combustion air 115 flowing through there is how the arrows 116 symbolize this. These fuel lines 108, 109 are preferably at the latest at the end of the tangential inflow Entry into the cone cavity 114, arranged to do this for an optimal Obtain air / fuel mixture. The one brought up through the fuel nozzle 103 As mentioned, fuel 112 is normally a liquid Fuel, forming a mixture with another medium, for example with a recirculated flue gas, is easily possible. That fuel 112 is in the cone cavity at a preferably very acute angle 114 injected. A conical fuel spray thus forms from the fuel nozzle 103 105, from the rotating combustion air flowing in tangentially 115 enclosed and dismantled. The concentration is then in the axial direction of the injected fuel 112 continuously through the inflowing combustion air 115 degraded to mix in the direction of evaporation. Becomes a introduced gaseous fuel 113 through the opening nozzles 117, the happens Formation of the fuel / air mixture directly at the end of the air inlet slots 119, 120. Is the combustion air 115 additionally preheated, or for example with a recycled flue gas or exhaust gas enriched, this supports sustainably the evaporation of the liquid fuel 112 before this mixture into the downstream stage flows, here in the transition piece 200 (see FIGS. 1 and 7). The same considerations also apply if liquid lines 108, 109 Fuels should be supplied. When designing the tapered partial body 101, 102 with regard to the cone angle and the width of the tangential air inlet slots 119, 120 are strict limits to be observed so that the desired Set the flow field of the combustion air 115 at the output of the swirl generator 100 can. Generally it can be said that a reduction in tangential Air inlet slots 119, 120 the faster formation of a backflow zone already in the Favored area of the swirl generator. The axial speed within the swirl generator 100 can be explained in more detail by a corresponding one in FIG. 2 (item 160) Increase or stabilize the described supply of an air quantity. A corresponding Swirl generation in operative connection with the downstream transition piece 200 (See FIGS. 1 and 7) prevents flow separation within of the mixing tube connected downstream of the swirl generator 100. The construction of the swirl generator 100 is furthermore excellently suitable, the size of the tangential Air inlet slots 119, 120 to change, so without changing the overall length of the swirl generator 100 covers a relatively large operational bandwidth can be. Of course, the partial bodies 101, 102 are also in another Plane can be moved relative to one another, which even provides an overlap thereof can be. It is also possible to pass through the partial bodies 101, 102 to interleave a counter-rotating movement in a spiral. Consequently it is possible to change the shape, size and configuration of the tangential air inlet slots 119, 120 to vary as desired, with which the swirl generator 100 is unchanged its overall length can be used universally.

4 shows, among other things, the geometric configuration of optional ones Baffles 121a, 121b. They have a flow initiation function these, according to their length, the respective end of the tapered partial body 101, 102 extend in the direction of flow towards the combustion air 115. The channeling of the combustion air 115 into the cone cavity 114 can be done by Open or close the guide plates 121a, 121b by one in the area of the entrance of this channel in the cone cavity 114 pivot point 123 optimized this is particularly necessary if the original gap size of the tangential air inlet slots 119, 120 should be changed dynamically, for example to change the speed of the combustion air 115 to reach. Of course, these dynamic arrangements can also be static can be provided by using a fixed component as required form the tapered partial body 101, 102.

5 shows, compared to FIG. 4, that the swirl generator 100 now consists of four partial bodies 130, 131, 132, 133 is constructed. The associated longitudinal symmetry axes for each sub-body are marked with the letter a. About this configuration can be said that they are due to the lower twist strength generated with it and in combination with a correspondingly enlarged slot width suitable, the bursting of the vortex flow on the downstream side of the swirl generator To prevent the mixing tube, so that the mixing tube best fulfills its intended role can meet.

FIG. 6 differs from FIG. 5 in that the partial bodies 140, 141, 142, 143 have a blade profile shape which is used to provide a certain Flow is provided. Otherwise, the mode of operation of the swirl generator is remained the same. The admixture of fuel 116 in the combustion air flow 115 happens from the inside of the blade profiles, i.e. the fuel line 108 is now integrated in the individual blades. They are here too Longitudinal axes of symmetry to the individual partial bodies marked with the letter a.

7 shows the transition piece 200 in a three-dimensional view. The transition geometry is corresponding for a swirl generator 100 with four partial bodies 5 or 6, built. Accordingly, the transition geometry points as Natural extension of the upstream part of the four transition channels 201 on, whereby the conical quarter surface of said partial body is extended until it cuts the wall of the mixing tube. The same considerations also apply if the swirl generator is based on a principle other than that described under FIG. 3, is constructed. The downward surface of the individual Transition channels 201 have a spiral path in the direction of flow Form, which describes a crescent-shaped course, according to the The fact that in the present case the flow cross section of the transition piece 200 flared in the direction of flow. The twist angle of the transition channels 201 in the flow direction is selected so that the pipe flow then up to for the cross-sectional jump at the combustion chamber inlet there is still a sufficiently large distance remains to achieve a perfect premix with the injected fuel. The measures mentioned above also increase the Axial speed on the mixing tube wall downstream of the swirl generator. The transition geometry and the measures in the area of the mixing tube cause one significant increase in the axial speed profile to the center of the mixing tube so that the danger of early ignition is decisively counteracted.

8 shows the tear-off edge already mentioned, which is formed at the burner outlet is. The flow cross-section of the tube 20 receives a transition radius in this area R, the size of which basically depends on the flow within the Tube 20 depends. This radius R is chosen so that the flow adjusts to the Puts on the wall and so the swirl number increases sharply. It can be quantified Define the size of the radius R so that it is> 10% of the inner diameter d of the tube is 20. Compared to a flow without a radius increases now the backflow bladder 50 tremendous. This radius R extends to the exit plane of the tube 20, the angle β between the beginning and end of the curvature <90 ° is. The tear-off edge A ins runs along one leg of the angle β Interior of the tube 20 and thus forms a demolition step S compared to the front Point of the tear-off edge A, the depth of which is> 3 mm. Of course, the here running parallel to the exit plane of the tube 20 edge using a curved Be brought back to the exit level. The angle β ' the between the tangent of the tear-off edge A and perpendicular to the exit plane of the pipe 20 is the same size as the angle β. The benefits of this training this tear-off edge go from EP-0 780 629 A2 under the chapter "Representation of the invention ". Another configuration of the tear-off edge for the same purpose can be achieved with toroid-like notches on the combustion chamber side.

LIST OF REFERENCE NUMBERS

10

Buchenring

20

Mixing tube, part of the mixing section 220

21

Holes, openings

30

combustion chamber

31

Openings

40

Flow, pipe flow in the mixing pipe, main flow

50

Backflow zone, backflow bubble

60

Brenner

100

swirl generator

101, 102

Partial conical body

101

Annular initial part

101b, 102b

Longitudinal axes of symmetry

103

fuel nozzle

104

fuel injection

105

Fuel spray (fuel injection profile)

108, 109

fuel lines

112

Liquid fuel

113

Gaseous fuel

114

conical cavity

115

Combustion air (combustion air flow)

116

Fuel injection from lines 108, 109

117

fuel nozzles

119, 120

Tangential air inlet slots

121a, 121b

baffles

123

Pivot point of the guide plates

130, 131, 132, 133

partial body

131a, 131a, 132a, 133a

Longitudinal axes of symmetry

140, 141, 142, 143

Vane-shaped partial body

140a, 141a, 142a, 143a

Longitudinal axes of symmetry

150

fuel concentration

160

Air volume, mixed air

161

Holes, openings

170

Fuel injectors

180

Annular air chamber

190

ring

200

Transition piece, part of the mixing section 220

201

Transition passages

220

mixing section

Claims (15)

1. Burner for operating a heat generator, the burner essentially comprising a swirl generator (100) for a combustion-air flow and means for injecting (103, 117) at least one fuel (112, 113) into the combustion-air flow (115), the means for injecting (103, 117) at least one fuel (112, 113) comprising at least one central fuel nozzle (103), arranged on the head side of the swirl generator (100), a mixing section (220) being arranged downstream of the swirl generator (100) and having, inside a first portion of the section in the direction of flow, a number of transition passages (201) for passing a flow formed in the swirl generator (100) into a mixing tube arranged downstream of these transition passages (201) and merging into a burner front, the swirl generator (100) having a ring (190) arranged around the central fuel nozzle (103), on the head side of the swirl generator (100), and the ring (190) having a number of bores (161) arranged in the circumferential direction,
   characterized in that
   fuel injectors (170) are arranged within the bores (161) of the ring (190), by means of which a fuel can be injected into an air quantity (160) flowing through the bores (161).
2. Burner according to Claim 1, characterized in that the bores (161) are directed so as to slant forwards.
3. Burner according to Claim 1, characterized in that the fuel nozzle (103) is surrounded by an annular air chamber (180).
4. Burner according to Claim 1, characterized in that the burner front of the mixing tube (20) to the downstream combustion chamber (30) is formed with a breakaway edge (A).
5. Burner according to Claim 1, characterized in that the number of transition passages (201) in the mixing section (220) corresponds to the number of partial flows formed by the swirl generator (100).
6. Burner according to Claim 1, characterized in that the mixing tube (20) arranged downstream of the transition passages (201) is provided with openings (21) in the direction of flow and in the peripheral direction for injecting an air flow into the interior of the mixing tube (20).
7. Burner according to Claim 6, characterized in that the openings (21) run at an acute angle relative to the burner axis (60) of the mixing tube (20).
8. Burner according to Claim 1, characterized in that the cross section of flow of the mixing tube (20) downstream of the transition passages (201) is less than, equal to or greater than the cross section of the flow (40) formed in the swirl generator (100, 100a).
9. Burner according to Claim 1, characterized in that a combustion chamber (30) is arranged downstream of the mixing section (220), in that there is a jump in cross section between the mixing section (220) and the combustion chamber (30), which jump in cross section induces the initial cross section of flow of the combustion chamber (30), and in that a backflow zone (50) can take effect in the region of this jump in cross section.
10. Burner according to Claim 1, characterized in that there is a diffuser and/or a venturi section upstream of the burner front (70).
11. Burner according to Claim 1, characterized in that the swirl generator (100) consists of at least two hollow, conical sectional bodies (101, 102; 130, 131, 132, 133; 140, 141, 142, 143) which are nested one inside the other in the direction of flow, in that the respective longitudinal symmetry axes (101b, 102b; 130a, 131a, 132a, 133a; 140a, 141a, 142a, 143a) of these sectional bodies run mutually offset in such a way that the adjacent walls of the sectional bodies form ducts (119, 120), tangential in their longitudinal extent, for a combustion-air flow (115), and in that at least one fuel nozzle (103) can take effect in the interior space (114) formed by the sectional bodies.
12. Burner according to Claim 11, characterized in that further fuel nozzles (117) are arranged in the region of the tangential ducts (119, 120) in their longitudinal extent.
13. Burner according to Claim 11, characterized in that the sectional bodies (140, 141, 142, 143) have a blade-shaped profile in cross section.
14. Burner according to Claim 11, characterized in that the sectional bodies have a fixed cone angle, increasing conicity, or decreasing conicity in the direction of flow.
15. Burner according to Claim 11, characterized in that the sectional bodies are nested spirally one inside the other.

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