EP0780629B1 - Burner for a heat generator - Google Patents

Abstract

The burner has a mixer section and a swirl generator. The mixer section (220) is positioned downstream from the swirl generator (100) and has, within a first part of the section (200) transfer ducts (201) running in the direction of flow for transmitting a current (40) formed in the swirl generator into a pipe situated downstream from the transfer ducts. The outlet plane of the pipe to the combustion chamber (30) has a break edge (A) for stabilising and enlarging a reverse current zone (50) formed downstream. The number of transfer ducts in the mixed section matches the number of art currents formed by the swirl generator. The pipe situated after the transfer ducts has openings (21) for injecting an air current into the pipe.

Description

Technical field

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

State of the art

EP-B1-0 321 809 describes a shell made of several shells conical burner, so-called double cone burner, for Generation of a closed swirl flow in the cone head has become known, which due to the increasing swirl along the cone tip becomes unstable and into an annular swirl flow with reverse flow in the core. Fuels such as gaseous fuels are produced along the the individual adjacent shells formed channels, too Called air inlet slots, injected and homogeneous with the Air mixes before combustion by ignition at the stagnation point the backflow zone or backflow bubble, which acts as a flame holder is used. Liquid fuels will be preferably injected via a central nozzle on the burner head and then evaporate in the cone cavity. Among those typical of gas turbines The ignition of these liquid fuels takes place under conditions early in the vicinity of the fuel nozzle, with what What cannot be avoided is that the NOx values are precisely due to this lack of premix increase sharply, for example it is necessary to inject water. About that It also had to be found that the attempt to contain hydrogen Burning gases similar to natural gas leads to pre-ignition problems at the gas wells with subsequent overheating of the burner. There is a remedy for this sought by using a special injection method at the burner outlet for such gaseous fuels is, the results of which have not been entirely satisfactory.

JP 07190308 A discloses one Burner with a swirl generator for application of a combustion air-fuel mixture with one Swirl. Following this swirl generator closes a tubular mixing section, which opens into a combustion chamber. Because of the geometric Design of the swirl generator is a conical Vortex formed at a point on the burner axis collapsed in the combustion chamber and there one circular flow to form a stable backflow zone evokes the stabilization of the flame serves.

Presentation of the invention

The invention seeks to remedy this. The invention how it is characterized in the claims, the task lies based on precautions for a burner of the type mentioned propose by which a perfect premix of fuels of various types and achieved which are reliable and optimal flame positioning is achieved.

The proposed burner has one on the head side and upstream Mixing section on a swirl generator, which is preferred can be interpreted in such a way that the aerodynamic Basic principles of the so-called double-cone burner according to EP-A1-0 321 809 can be used. Basically, however, is that Use of an axial or radial swirl generator possible. The mixing section itself preferably consists of a tubular one Mixing element, hereinafter called mixing tube, which a perfect premixing of different fuels Kind allowed.

The flow from the swirl generator is seamless into the mixing tube initiated: This happens through a transition geometry, which consists of transition channels, which in the initial phase this mixing tube are excluded, and which the flow in the subsequent effective flow cross-section transfer the mixing tube. This low loss Flow initiation between swirl generator and mixing tube prevented first the immediate formation of a backflow zone at the exit of the swirl generator.

First, the swirl strength in the swirl generator is above its Geometry chosen so that the vertebra does not burst in the mixing tube, but further downstream at the combustion chamber inlet takes place, the length of this mixing tube dimensioned so is that there is sufficient mix quality for everyone Fuel types results. For example, is the one used Swirl generator according to the basic principles of the double-cone burner built up, the twist strength results from the design the corresponding cone angle, the air inlet slots and their number.

The axial speed profile has a pronounced profile in the mixing tube Maximum on the axis and thereby prevents backfire in this area. The axial speed drops down to the wall. To reignite this area too prevent various measures are provided: For example, on the one hand, the entire speed level by using a mixing tube with a sufficient Lift small diameter. Another possibility consists of only the outside speed of the Increase mixing tube by a small part of the combustion air over an annular gap or through filming holes flows into the mixing tube downstream of the transition channels.

As for the mentioned transition channels to initiate the flow affects from the swirl generator in the mixing tube, so to say that the course of these transition channels is spiral can be constricting or expanding accordingly the effective subsequent flow cross-section of the mixing tube.

Part of the pressure loss that may be generated can be caused by Attachment of a diffuser at the end of the mixing tube compensated become. In this area or upstream one can also Venturi range can be provided.

The combustion chamber closes at the end of the mixing tube a cross-sectional leap. A central one is formed here Backflow zone, the properties of which are those of a flame holder are. The creation of a stable backflow zone requires one sufficiently high swirl number in the mixing tube. But it is one Initially undesirable, stable backflow zones can occur the supply of small, strongly swirled air volumes, 5-20% of the Total air volume generated at the end of the pipe.

a) Stabile Flammenposition;

b) Tiefere Schadstoff-Emissionen (Co, UHC, NOx);

c) Minimierung der Pulsationen;

d) Vollständiger Ausbrand;

e) Grosse Betriebsbereich-Abdeckung;

f) Gute Querzündung zwischen den verschiedenen Brennern, insbesondere bei gestufter Lasterstellung, bei welcher die Brenner untereinander interdependent betrieben werden;

g) Die Flamme kann der entsprechenden Brennkammergeometrie angepasst werden;

h) Kompakte Bauweise;

i) Verbesserte Mischung der Strömungsmedien;

j) Verbesserter "Patternfaktor" der Temperaturverteilung in der Brennkammer (= ausgeglichener Temperaturprofil der Brennkammerströmung).

In connection with the mentioned cross-sectional jump, the end of the mixing tube is formed with a tear-off edge, which gives the backflow zone a high spatial stability. In general, the measures mentioned can achieve the following advantages:

a) Stable flame position;

b) Lower pollutant emissions (Co, UHC, NOx);

c) minimization of pulsations;

d) complete burnout;

e) Large operating area coverage;

f) Good cross-ignition between the different burners, especially with stepped load position, in which the burners are operated interdependently with one another;

g) The flame can be adapted to the corresponding combustion chamber geometry;

h) compact design;

i) Improved mixing of the flow media;

j) Improved "pattern factor" of the temperature distribution in the combustion chamber (= balanced temperature profile of the combustion chamber flow).

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

In the following, exemplary embodiments are described with reference to the drawings the invention explained in more detail. All for the immediate Understand the invention are non-essential features been left out. The same elements are in the different Figures with the same reference numerals. The The direction of flow of the media is indicated by arrows.

Brief description of the drawings

Fig. 1

einen Brenner mit anschliessender Brennkammer,

Fig. 2

einen Drallerzeuger in perspektivischer Darstellung, entsprechend aufgeschnitten,

Fig. 3

einen Schnitt durch den 2-Schalen-Drallerzeuger, nach Fig. 2,

Fig. 4

einen Schnitt durch einen 4-Schalen-Drallerzeuger,

Fig. 5

einen Schitt durch einen Drallerzeuger, dessen Schalen schaufelförmig profiliert sind,

Fig. 6

eine Darstellung der Form der Uebergangsgeometrie zwischen Drallerzeuger und Mischrohr und

Fig. 7

eine Abrisskante zur räumlichen Stabilisierung der Rückströmzone.

It shows:

Fig. 1

a burner with subsequent combustion chamber,

Fig. 2

a swirl generator in a perspective view, cut open accordingly,

Fig. 3

3 shows a section through the 2-shell swirl generator, according to FIG. 2,

Fig. 4

a section through a 4-shell swirl generator,

Fig. 5

a step through a swirl generator, the shells of which are profiled in a shovel shape,

Fig. 6

a representation of the shape of the transition geometry between swirl generator and mixing tube and

Fig. 7

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

Ways of carrying out the invention, commercial usability

Fig. 1 shows the overall structure of a burner. Is initially a swirl generator 100 effective, the design of which in the following Fig. 2-5 shown and described in more detail becomes. This swirl generator 100 is a conical one Formations that are tangential multiple times from a tangential inflowing combustion air flow 115 is applied becomes. The flow that forms here is based on a transition geometry provided downstream of the swirl generator 100 transitioned seamlessly into a transition piece 200, in such a way that no separation areas can occur there. The configuration of this transition geometry is under Fig. 6 described in more detail. This transition piece 200 is on the outflow side the transition geometry through a tube 20 extended, both parts of the actual mixing tube 220, also called mixing section, form the burner. Of course the mixing tube 220 may consist of a single piece, i.e. then that the transition piece 200 and pipe 20 merged into a single coherent structure with the characteristics of each part preserved stay. Become transition piece 200 and tube 20 from two parts created, they are connected by a socket ring 10, the same bushing ring 10 on the head side as the anchoring surface serves for the swirl generator 100. Such a Socket ring 10 also has the advantage that different Mixing tubes can be used. Outflow side of the tube 20 is the actual combustion chamber 30, which only symbolizes here through the flame tube is. The mixing tube 220 meets the condition that downstream of the swirl generator 100 provides a defined mixing section in which a perfect premix of fuels of different types is achieved. This mixing section, so the mixing tube 220, furthermore enables a loss-free Flow guidance, so that also in operative connection do not initially form a backflow zone with the transition geometry can, which over the length of the mixing tube 220 to the Mix quality for all types of fuel influence can be exercised can. This mixing tube 220 has yet another Property, which is that in the mixing tube 220 even the axial speed profile is a pronounced maximum owns on the axis, so that the Flame from the combustion chamber is not possible. However it is correct that with such a configuration this axial speed drops to the wall. To reignite also in To prevent this area, the mixing tube 220 in Flow and circumferential direction with a number regularly or irregularly distributed holes 21 of the most varied Provide cross sections and directions through which an amount of air flows into the interior of the mixing tube 220, and along the wall in the sense of a filming an increase in speed induce. Another way the same To achieve effect is that the flow cross section of the mixing tube 220 on the outflow side of the transition channels 201, which has the transition geometry already mentioned form, narrowing, causing the whole Speed level increased within the mixing tube 220 becomes. In the figure, these bores 21 run under one acute angle with respect to the burner axis 60. Furthermore the outlet of the transition channels 201 corresponds to the narrowest Flow cross section of the mixing tube 220. The above Transition channels 201 therefore bridge the respective cross-sectional difference, without making the flow negative to influence. If the precaution chosen by the Guiding the pipe flow 40 along the mixing pipe 220 triggers intolerable pressure loss, can counter this Remedial action can be taken by placing one at the end of the mixing tube Diffuser not shown in the figure is provided. At the A combustion chamber 30 closes at the end of the mixing tube 220 , with a between the two flow cross-sections Cross-sectional jump is present. Only here does one form central backflow zone 50, which has the properties of a Has flame holder. Forms within this cross-sectional jump a flow during operation Edge zone, in which by the prevailing negative pressure Vertebral detachments occur, so this leads to an increased Ring stabilization of the backflow zone 50 the combustion chamber 30 has a number of openings 31 through it which an amount of air directly into the cross-sectional jump streams, and there lower others help that Ring stabilization of the backflow zone 50 is strengthened. Besides It should not go unmentioned that the generation of a stable Backflow zone 50 also has a sufficiently high swirl number in a pipe requires. If this is initially undesirable, so stable return flow zones can be made smaller by the supply strongly swirled air flows at the pipe end, for example through tangential openings. Here you go here assume that the amount of air required for this is approximately 5-20% of the total air volume. As for the design of the Tear edge at the end of the mixing tube 220 is concerned the description referenced in FIG. 7.

In order to better understand the structure of the swirl generator 100 it is advantageous if, at the same time as FIG. 2, at least FIG. 3 is used. Furthermore, this Fig. 2 is not unnecessary to be confusing, they are those according to the Figure 3 schematically shown guide plates 121a, 121b only hinted been recorded. In the following, the Description of Fig. 2 as required on the figures mentioned pointed out.

The first part of the burner according to FIG. 1 forms the one according to FIG. 2 shown swirl generator 100. This consists of two hollow conical partial bodies 101, 102 which are offset from one another are nested. The number of conical Partial body can of course be larger than two, such as Figures 4 and 5 show; this depends on how each further will be explained in more detail below, depending on the type of debt collection of the whole burner. It is with certain operating constellations not excluded one from one single spiral existing swirl generator. The Offset of the respective central axis or longitudinal symmetry axes 201b, 202b of the tapered partial bodies 101, 102 to one another creates a mirror image of the neighboring wall Arrangement, each a tangential channel, i.e. an air inlet slot 119, 120 (Fig. 3) through which the combustion air 115 inside the swirl generator 100, i.e. in flows through the cone cavity 114 thereof. The cone shape of the one shown Partial body 101, 102 has a flow direction certain fixed angle. Of course, depending on the operational use, can the partial body 101, 102 in the direction of flow have an increasing or decreasing taper similar to a trumpet or Tulip. The latter two Shapes are not included in the drawing as they are for the expert can be easily understood. The two tapered partial bodies 101, 102 each have a cylindrical Initial part 101a, 102a, which also, analogous to the tapered Partial bodies 101, 102, offset from one another, so that the tangential air inlet slots 119, 120 via the entire length of the swirl generator 100 are present. In the area of the cylindrical initial part, a nozzle 103 is preferred for a liquid fuel 112, the injection of which 104 with the narrowest cross section of the through conical partial body 101, 102 formed conical cavity 114 coincides. The injection capacity and the type of this Nozzle 103 depends on the specified parameters of the respective burner. Of course, the swirl generator can 100 purely conical, i.e. without cylindrical starting parts 101a, 102a. The tapered body 101, 102 also each have a fuel line 108, 109 on which along the tangential air inlet slots 119, 120 arranged and provided with injection openings 117 are, by which preferably a gaseous fuel 113 injected into the combustion air 115 flowing through there is how the arrows 116 symbolize this. This Fuel lines 108, 109 are preferably at the latest End of tangential inflow, before entering the cone cavity 114, placed, this for an optimal Obtain air / fuel mixture. At that through the nozzle 103 fuel introduced 112, as mentioned, normally a liquid fuel, whereby a mixture formation with another medium without any problems is possible. This fuel 112 will tip under one Angle injected into the cone cavity 114. From the nozzle 103 A conical fuel spray 105 is thus formed, which by the rotating combustion air 115 flowing in tangentially is enclosed. In the axial direction, the concentration of the injected fuel 112 continuously through the inflowing Combustion air 115 to mix direction Evaporation reduced. If a gaseous fuel 113 Formed through the opening nozzles 117, the formation occurs of the fuel / air mixture directly at the end of the air inlet slots 119, 120. Is the combustion air 115 additional preheated, or for example with a recirculated This enriches flue gas or exhaust gas sustained evaporation of the liquid fuel 112, before this mixture flows into the downstream stage. The The same considerations also apply when using the lines 108, 109 liquid fuels should be supplied. At the design of the tapered partial body 101, 102 with respect the cone angle and the width of the tangential air inlet slots 119, 120 are strict limits to be observed, so that the desired flow field of the combustion air Set 115 at the output of swirl generator 100 can. Generally speaking, a downsizing of the tangential air inlet slots 119, 120 the faster Formation of a backflow zone already in the area of the swirl generator favored. The axial speed within the Swirl generator 100 cannot be replaced by a corresponding one change the supply of an axial combustion air flow shown. Appropriate swirl generation prevents formation of flow separation within the swirl generator 100 downstream mixing tube. The construction of the swirl generator 100 is also excellent, the size to change the tangential air inlet slots 119, 120, with which without changing the overall length of the swirl generator 100 a relatively wide range of operations can be covered can. Of course, the partial bodies 101, 102 are also in another level slidable to each other, which even an overlap of the same can be provided. It is further possible, the partial body 101, 102 by an opposite to interleave rotating movement in a spiral. So it is possible to change the shape, size and the configuration of the tangential air inlet slots 119, 120 to vary arbitrarily, with which the swirl generator 100 without Changing its overall length is universally applicable.

The geometric configuration of FIG Baffles 121a, 121b. They have a flow initiation function these, according to their length, the respective End of the tapered partial body 101, 102 in the direction of flow extend towards the combustion air 115. The Channeling the combustion air 115 into the cone cavity 114 can by opening or closing the guide plates 121a, 121b by one in the area of the entry of this channel into the Cone cavity 114 placed pivot point 123 can be optimized, this is particularly necessary if the original gap size of the tangential air inlet slots 119, 120 dynamic should be changed. Of course you can dynamic arrangements can also be provided statically by required guide plates with a fixed component form the tapered partial bodies 101, 102. The can also Swirl generator 100 can also be operated without baffles, or other aids can be provided for this.

4 shows that the swirl generator 100 now made up of four partial bodies 130, 131, 132, 133 is. The associated longitudinal symmetry axes for each partial body are marked with the letter a. About this configuration can be said that because of the generated lower twist strength and in cooperation with one suitably suitably enlarged slot width, the bursting of the vortex flow on the downstream side of the To prevent swirl in the mixing tube, making the mixing tube can best fulfill the role intended for him.

Fig. 5 differs from Fig. 4 in so far as here the partial bodies 140, 141, 142, 143 have a blade profile shape, which is intended to provide a certain flow becomes. Otherwise, the mode of operation of the swirl generator stayed the same. The admixture of fuel 116 in the combustion air flow 115 happens from the inside the blade profiles out, i.e. the fuel line 108 is now integrated in the individual blades. Also here are the longitudinal axes of symmetry to the individual partial bodies marked with the letter a.

6 shows the transition piece 200 in a three-dimensional view. The transition geometry is for a swirl generator 100 with four partial bodies, corresponding to FIG. 4 or 5, built up. Accordingly, the transition geometry points as natural extension of the upstream parts four transition channels 201 on, making up the cone quarter area the partial body mentioned is extended until it hits the wall of the tube 20 respectively. of the mixing tube 220 cuts. The same Considerations also apply when the swirl generator is off another principle than that described under Fig. 2, is constructed. The one running downward in the direction of flow The area of the individual transition channels 201 has an in Flow direction on a spiral shape, which describes a crescent shape, corresponding to the The fact that the flow cross section of the Transition piece 200 flared in the direction of flow. The swirl angle of the transition channels 201 in the flow direction is selected so that the pipe flow then up to A cross-sectional jump at the combustion chamber inlet is still sufficient large distance remains to make a perfect premix with to manage the injected fuel. Further increases the axial speed is also affected by the above-mentioned measures on the mixing tube wall downstream of the swirl generator. The transition geometry and the measures in the area of the mixing tube cause a significant increase in the axial speed profile towards the center of the mixing tube, so that the danger of early ignition is decisively counteracted becomes.

Fig. 7 shows the tear-off edge already mentioned, which on Burner outlet is formed. The flow cross section of the Tube 20 is given a transition radius R in this area, whose size basically depends on the flow within the Tube 20 depends. This radius R is chosen so that the flow applies to the wall and so the swirl number strong can rise. The size of the radius can be quantified Define R so that it is> 10% of the inner diameter d of the tube is 20. Opposite a flow without a radius Now the backflow bladder 50 increases enormously. This Radius R extends to the exit plane of the tube 20, wherein the angle β between the beginning and end of the curvature is <90 °. The runs along one leg of the angle β Tear-off edge A into the interior of the tube 20 and thus forms one Tear-off step S opposite the front point of the tear-off edge A, whose depth is> 3 mm. Of course, here edge running parallel to the exit plane of the tube 20 a curved course again at the exit level to be brought. The angle β 'that is between tangent the trailing edge A and perpendicular to the exit plane of the Tube 20 spreads is the same size as angle β. On the Advantages of this training is already under the chapter "Presentation of the invention" discussed in more detail.

Reference list

10th

Beech ring

20th

pipe

21

Holes, openings

30th

Combustion chamber

31

Openings

40

Flow, pipe flow in the mixing pipe

50

Backflow zone, backflow bubble

60

Burner axis

100

Swirl generator

101, 102

Partial body

101a, 102b

Cylindrical starting parts

101b, 102b

Longitudinal symmetry axes

103

Fuel nozzle

104

Fuel injection

105

Fuel spray (fuel injection profile)

108, 109

Fuel lines

112

Liquid fuel

113

Gaseous fuel

114

Cone 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 symmetry axes

140, 141, 142, 143

Vane-shaped partial body

140a, 141a, 142a, 143a

Longitudinal symmetry axes

200

Transition piece

201

Transition channels

220

Mixing tube

d

Inner diameter of the tube 20

R

Transition radius

T

Tangent line of the tear-off edge

A

Tear-off edge

S

Demolition level

β

Transition angle from R

β '

Angle between T and A

Claims (14)

1. Burner for a heat generator, substantially consisting of a swirl generator (100) for a combustion air flow and of means for injecting a fuel through nozzles into said combustion air flow, wherein a mixing length (220) is disposed downstream of said swirl generator (100),
   characterized in
   that said mixing length (220) comprises transfer ducts (201) extending in the flow direction within a first length section (200) for transferring a flow (40) created in said swirl generator (100) into a tube (20) connected downstream of said transfer ducts (201), and that the discharge plane of this tube (20) towards the combustion chamber (30) is configured to present a breakaway edge (A) for stabilising and enlarging a backflow zone (50) forming in the downstream region.
2. Burner according to Claim 1, characterised in that the number of said transfer ducts (201) in said mixing length (220) corresponds to the number of partial flows formed by said swirl generator (100).
3. Burner according to Claim 1, characterised in that said tube (20) joined downstream of said transfer ducts (201) is provided with openings (21) in the flow direction and peripheral direction for injecting an air flow through nozzles into the interior of said tube (20).
4. Burner according to Claim 3, characterised in that said openings (21) extend at an acute angle relative to the burner axis (60) of said tube (20).
5. Burner according to Claim 1, characterised in that said breakaway edge (A) consists of a transition radius (R) in the region of the discharge plane of said tube (20) and of a breakaway step (S) offset from the discharge plane of said tube (20).
6. Burner according to Claim 5, characterised in that said transition radius (R) amounts to > 10 % of the inside diameter of said tube (20), and that said breakaway step (S) has a depth of > 3 mm.
7. Burner according to Claim 1, characterised in that the flow cross-section of said tube (20) downstream of said transfer ducts (201) is smaller than, equal to or larger than the cross-section of the flow (40) created in said swirl generator (100).
8. Burner according to Claim 1, characterised in that downstream of said mixing length (220) a combustion chamber (30) is disposed, that a cross-section discontinuity is provided between said mixing length (220) and said combustion chamber (30), that induces the initial flow cross-section of said combustion chamber (30), and that a backflow zone (50) is provided for becoming operative in the region of this cross-section discontinuity.
9. Burner according to Claim 1, characterised in that a diffuser and/or a Venturi section is provided upstream of said breakaway edge (A).
10. Burner according to Claim 1, characterised in that said swirl generator (100) consists of at least two hollow conical body segments (101, 102; 130, 131, 132, 133; 140, 141, 142, 143) nested into each other, that the respective axes of longitudinal symmetry (101b, 102b; 130a, 131a, 132a, 133a; 140a, 141a, 142a, 143a) of these body segments extend in a mutually offset position such that the adjacent walls of said body segments form tangential ducts (119, 120) for a combustion air flow (115) along their longitudinal extension, and that at least one fuel nozzle (103) is disposed in the conical hollow space (114) formed by said body segments.
11. Burner according to Claim 10, characterised in that further fuel nozzles (117) are disposed in the region of said tangential ducts (119, 120) along the longitudinal extension thereof.
12. Burner according to Claim 10, characterised in that said body segments (140, 141, 142, 143) present a blade-shaped profiling in their cross-section.
13. Burner according to Claim 10, characterised in that said body segments present a fixed cone angle, or an increasing cone inclination, or a decreasing cone inclination along the flow direction.
14. Burner according to Claim 10, characterised in that said body segments are spirally nested into each other.

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