EP0775869B1 - Premix burner - Google Patents

Description

Technical field

The invention relates to a premix burner for combustion of gaseous and / or liquid fuel, in which the fuel as a secondary flow in a gaseous, channeled main flow is injected, the secondary flow has a much smaller mass flow than the mainstream.

State of the art

A premix burner is known from EP 0 321 809 B1 due to low NOx emission values (approx. 25 ppm) and a high one Flame stability distinguishes. This premix burner, too Called double cone burner, consists of hollow, one into one Partial conical bodies with tangential air inlet slots for the combustion air flowing in from the compressor on and feeders for gaseous and liquid Fuels, the central axes of the hollow partial cone body a widening taper in the direction of flow have and offset to each other in the longitudinal direction run. Inside the burner (cone tip) is one Fuel nozzle arranged for the liquid fuel through which the fuel at an acute angle into the hollow cone is injected. The resulting tapered liquid fuel profile is caused by the tangentially rotating combustion air flow enclosed, the concentration in the axial direction of fuel as a result of mixing with the combustion air is constantly decreasing. The premix burner can too operated with gaseous fuel or in mixed operation become. The mixture of the gaseous forms Fuel with the combustion air already in the tangential Air inlet slots into which the gaseous fuel is introduced via uniformly distributed nozzles.

To ensure reliable ignition of the mixture at the exit of the Achieving burners and sufficient burnout is one an intimate mixture of fuel and air is required. The type of injection creates inside the double-cone burner axially aligned vortex of the fuel / air mixture. If the vortex number is a critical value has reached, the vortex breakdown takes place Vortex) and it forms downstream of the burner outlet stable flame front.

Another permanent reduction in pollutant emissions the double cone burner, for example to NOx values less than 9 ppm due to changes in operating conditions because of the problems with flame stability, Pulsation and the ever higher combustion temperatures not possible.

Another disadvantage of the double-cone burner is its complicated geometric shape and the resulting manufacturing difficulties.

EP 0 619 456 A1 describes a fuel supply system for a Combustion chamber with premix combustion known, in which a gaseous and / or liquid fuel as a secondary flow injected into a gaseous, channeled main flow is, the secondary flow being a much smaller one Mass flow has as the main flow and where the flows through premix channel curved walls. In a Embodiment, the channel is annular and on the outer as well as inner ring wall are an equal number of vortex generators strung together in the circumferential direction.

These vortex generators point three in the direction of flow extending, freely flowed areas, one of which the roof and the other two form the side surfaces. The side surfaces are flush with the same duct wall and together form an arrow angle α. The roof area lies with a sell across the channel Edge on the same duct wall as the side surfaces and the longitudinal edges of the roof surface that are flush are with the longitudinal ones protruding into the flow channel Edges of the side surfaces run under one Angle of attack Θ to the duct wall. They are also half vortex generators possible where only one of the two side surfaces of the vortex generator with an arrow angle α / 2 while the other side is straight and in Flow direction is aligned. The connecting edges of Two opposite vortex generators can do this lie on the same radial or by half a division be offset.

With this known fuel supply system according to EP 0 619 456 A1 is achieved that combustion air in a very short distance and fuel are intimately mixed and at the same time in the Mixing zone achieved an even speed distribution becomes. Statements regarding reaching a sufficient Flame stability is missing here. Because this fuel delivery system used for a self-igniting combustion chamber is not flame stabilization in this case necessary.

From US 5 351 477 a device for premixing air and fuel is in a mixing channel prior to combustion in gas turbines known with a number of inner and outer independent and opposite to each other rotating vortex generators. The outer vortex generators also contain blades Openings for the supply of liquid or gaseous fuel. Compressed air is introduced into the mixing channel via the inner and outer vortex generators, to create an intense shear area. The high pressure air becomes uniform there mixed with the fuel, minimizing contamination during combustion arise. However, the flame stability that can be achieved here is not always sufficient.

Presentation of the invention

The invention has for its object a premix burner for the combustion of gaseous and / or liquid To develop fuel with extremely low NOx emissions can be reached, the burner is characterized by a simple geometry and reliable operating behavior should honor. The burner is said to be within shortest Stretch an intimate mixture of combustion air and Fuel can be achieved with more uniform at the same time Speed distribution in the mixing zone, also with such a burner without using a mechanical Flame holder is certain to kick back the flame should be avoided.

According to the invention, this is according to a premix burner Preamble of claim 1, which with a fuel supply system works, which is known from EP 0 619 456 A1 is achieved in that the vortex generators used generate such vortices, which after mixing the Fuel with the air of the fuel / air mixture flow leave a residual vortex that of the canal walls formed annular main flow channel with a constant Height a length downstream of the vortex generators and the fuel injection, which in the area between the 5 to 20 times its height and that the ring-shaped Main flow channel then by closing the inner cylinder wall to a circular main flow channel expanded.

The advantages of the invention are that Fuel supply system and the use of vortex generators on the one hand an intensive complete mixture of fuel and combustion air in a very short mixing section without transfer areas and with a uniform speed profile takes place, which is a prerequisite for minimization is the NOx content and that on the other hand due to the the vortex generators generated residual vertebrae after the Mixture still present in the fuel / air mixture flow is what affects the recirculation zone positively the flame stability increases and the cross mix of the different Improved burner in an annular combustion chamber. The annular premix burner according to the invention is characterized by a simple geometry and is therefore structurally easy to manufacture.

To form the recirculation zone, which is used as an ignition source serves for incoming fresh fuel / air mixture, it is also necessary that after a sufficient Length of the annular pre-mix section of the inner cylinder closes. This can be done gradually in a convenient manner or take place suddenly, so that the main flow channel either gradually expanded or a sudden one Transition from the ring channel to the circular channel. The recirculation zone then forms in a circular cross-section.

It is advantageous if "half" vortex generators of the Deltawing type be used with a vortex generator has three freely flowing surfaces, which are in the direction of flow extend and one of which is the roof area and the the other two form the side faces that the side faces are flush with the same duct wall and one side surface is provided with a half arrow angle, while the other side surface is aligned straight and in the direction of flow is that the roof area with a cross to the flow Ring channel running edge on the same channel wall rests like the side faces, and that the longitudinal Edges of the roof surface that are flush with those in the Flow channel protruding longitudinal edges of the Side surfaces run at an angle to the duct wall.

When using this type of vortex generators working in the circumferential direction are strung together, they combine Vertebrae, which all have the same sense of rotation, in one large rotating vortex.

Finally, vortex generators are an advantage in the premix burner arranged, which is approximately the shape of a rectangular Have triangle of small thickness, the two flowed around triangular side surfaces parallel to each other run and together with the roof surface the connecting surface include, the roof surface with an edge and the Connection surface with an edge on the same duct wall fit like the two side walls.

These vortex generators are beyond the scope of the two Cylinder walls arranged evenly distributed and so that that two opposite vortex generators each around half a pitch are offset, then the twist direction on the opposite vortex generators the same and the mainstream is forced to swirl a lot, of both for a complete mix with the Fuel is enough, as well as a residual vortex for flame stabilization provides.

Further advantages of the invention emerge from the subclaims.

Brief description of the drawing

In the drawing are several embodiments of the invention shown schematically.

Fig. 1

einen Längsschnitt eines erfindungsgemässen Vormischbrenners;

Fig. 2

einen Teillängsschnitt einer zweiten Ausführungsvariante des Vormischbrenners;

Fig. 3

einen Teillängsschnitt einer dritten Ausführungsvariante des Vormischbrenners;

Fig. 4

eine perspektivische Darstellung eines "halben" Wirbel-Generators des Delta-Flügel-Typs;

Fig. 5

eine perspektivische Darstellung einer anderen Ausführungsvariante des Wirbel-Generators;

Fig. 6

eine perspektivische Darstellung einer weiteren Ausführungsvariante des Wirbel-Generators;

Fig. 7

eine Anordnungsvariante der Wirbel-Generatoren nach Fig. 4 im Ringkanal;

Fig. 8

eine weitere Anordnungsvariante der Wirbel-Generatoren nach Fig. 4 im Ringkanal;

Fig. 9

eine Anordnungsvariante der Wirbel-Generatoren nach Fig. 6 im Ringkanal;

Fig. 10

eine Anordnungsvariante der Wirbel-Generatoren nach Fig. 5 im Ringkanal.

Show it:

Fig. 1

a longitudinal section of a premix burner according to the invention;

Fig. 2

a partial longitudinal section of a second embodiment of the premix burner;

Fig. 3

a partial longitudinal section of a third embodiment of the premix burner;

Fig. 4

a perspective view of a "half" vortex generator of the delta wing type;

Fig. 5

a perspective view of another embodiment of the vortex generator;

Fig. 6

a perspective view of a further embodiment of the vortex generator;

Fig. 7

an arrangement variant of the vortex generators according to Figure 4 in the ring channel.

Fig. 8

a further arrangement variant of the vortex generators according to Figure 4 in the ring channel.

Fig. 9

a variant of the arrangement of the vortex generators of Figure 6 in the ring channel.

Fig. 10

a variant of the arrangement of the vortex generators according to FIG. 5 in the ring channel.

It is only essential for understanding the invention Elements shown. Not essential to the invention are not shown Elements such as housings, fastenings and Cable bushings. The flow direction of the work equipment is marked with arrows.

Way to implement the invention

The invention is described below using exemplary embodiments and FIGS. 1 to 10 explained in more detail.

1 shows a possible embodiment in a longitudinal section of the annular premix burner according to the invention. He consists essentially of two cylinders with each other different diameters, which are concentric to each other are arranged so that the inner cylinder wall 21a and outer cylinder wall 21b delimit an annular channel 20. in the Vortex generators 9 are arranged, their shape and mode of action described below becomes. The channel 20 has a constant height H and has a length L downstream of the vortex generators, which in the Range between 5 and 20 times its height H and the premixing section for combustion air 1 and gaseous Fuel 2 forms. Via piping 3 is immediate downstream of the vortex generators 9 gaseous fuel 2 via openings 4 in the outer cylinder wall 21b as a secondary flow injected into the main flow of the ring channel 20 and mixed with the combustion air 1. The contribution the gaseous fuel 2 could of course also on the inner cylinder wall 21a or best on both Walls 21a and 21b take place, as in the lower part of Fig. 1 is shown.

The variant shown in FIG. 1 closes the premixing section gradually the inner cylinder wall 21a, so that the inner cylinder is completed by a cone tip becomes. The outer cylinder wall 21b narrows in the area the cone tip first, before moving on encloses a circular cross section in which forms a recirculation zone that acts as an ignition source for incoming fresh fuel / air mixture is used.

2 is a further embodiment variant of the annular Premix burner shown. In contrast to Fig. 1 here the inner cylinder closes after a sufficient long premixing section (length L is approx. 5 to 20 times the channel height H) suddenly, so that the transition from the ring channel 20 to the circular channel, in which the recirculation zone 22 trained, abruptly. The gaseous fuel 2 is here through openings on the inner and outer cylinder attached immediately downstream of the vortex generators 9 annular fuel supply lines 5 as Secondary flow into that swirled by the vortex generators Main flow introduced and intense with the air mixed.

3 shows a third variant of the premix burner. As in the examples above, here too Ring channel 20 vortex generators 9 arranged, via which Air 1 is carried as the main flow and swirled before immediately downstream of the vortex generators 9 gaseous Fuel is injected. To enhance the vortex effect are upstream of the vortex generators 9 deflection blades 8 arranged in the ring channel 20. The same effect can be achieved when the main flow is tangential over the annulus Slots (not shown here) enters the annular space 20 and thereby receives a tangential speed component. The inner cylinder also closes gradually here however not to a cone tip, but to one Hemisphere. In the inner cylinder there are lines 6 for the supply of liquid fuel 7 arranged which at the end the premixing section for the combustion air 1 and the gaseous one Fuel 2 from in the hemispherical end of the inner Cylinder arranged nozzles in the circular cross section the burner is injected.

Of course, in another, not drawing shown embodiment instead of the injection of gaseous fuel 2 in the annular channel 20 also liquid Fuel 7, for example introduced via a fuel lance and are swirled by the vortex generators Air in the annular space 20 are mixed.

The vortex generators 9 installed in the ring channel 20 can have different shapes. Essential to the invention is that they create longitudinal vortices with no recirculation area and therefore a complete one within the shortest distance Enable the fuel to be mixed with the combustion air, on the other hand, after mixing in a residual vortex the flow remains, which runs along the wake of the inner Cylinder is present. This residual vortex affects the recirculation zone and on the one hand ensures a high Flame stability and on the other hand for a good cross mix of the various burners in the ring combustion chamber.

The schematically depicted in the above exemplary embodiments Vortex generators 9 are half delta wings, i.e. (see FIG. 4) that a vortex generator 9 freely flowed around three Surfaces 10, 11, 12 which extends in the direction of flow extend and one of which is the roof surface 10 and the other two form the side surfaces 11, 13 that the Side surfaces 11, 13 flush with the same channel wall 21 are and a side surface 11 provided with an arrow angle α / 2 while the other side surface 13 is straight and in Direction of flow is aligned that the roof surface 10 with an edge running transversely to the channel 20 through which flow flows 15 abuts the same channel wall 21 as the side surfaces 11, 13, and that the longitudinal edges 12, 14 of the roof surface 10, which are flush with those in the flow channel 21 protruding longitudinal edges of the side surfaces 11, 13 run at an angle of attack Θ to the channel wall 21. The two side surfaces 11, 13 comprise a connecting edge 16 with each other, which together with the longitudinal Edges 12, 14 of roof surface 10 form a tip 18, the connecting edge in the radial of the curved channel wall 21 runs. The connecting edge 16 and / or the longitudinal edges 12, 14 of the roof surface 10 are there at least approximately sharp.

In Figures 4 to 6 is the actual channel that of one flows through the main flow symbolized by a large arrow is not shown.

It is advantageous if the connecting edge 16 of the in the Fig. 4 described vortex generators 9 the downstream Edge of the vortex generator 9 forms and the transverse to the flow Channel 20 extending edge 15 of the roof surface 10 die edge first acted on by the main flow is because the vertebra can build up particularly well.

The vortex generator works as follows: Flow around the edge 14 of the half arrow angle α / 2 provided side surface 11, the main flow into one Vortex converted, its axis in the axis of the main flow lies. On the straight side surface 13 in the direction of flow the main flow is aligned, there will be no vortex generated so that a swirl is forced on the flow and there is no vortex-neutral field. Will now be immediate downstream of the vortex generators 9 the fuel as described above introduced as a secondary flow into the main flow, this leads to an intensive mixing of the combustion air 1 and fuel 2.

5 shows a further embodiment of a vortex generator 9a, which for the premix burner according to the invention can be used. The vortex generator 9a has approximately the shape of a rectangular triangle of small thickness on, the two flowed around triangular side surfaces 11, 13 run parallel to each other and together with the Roof surface 10 comprise the connecting surface 19, the Roof surface 10 with an edge 15 and the connecting surface 19 rest with an edge 17 on the same channel wall as that two side walls 11, 13 and the side surfaces 11, 13 with the main flow direction of the incoming air form β. The roof surface 10 can also be concave or convex curved his. This has 9a compared to vortex generators with a straight roof surface the advantage of being the same Vortex strength can be generated with a lower pressure drop can. Another advantage of the vortex generators 9a is in that they are extremely easy to manufacture, for example by punching out thin sheets. Because the width the roof area 10 in the vortex generators 9a is small is, vortex formation practically only occurs on one Side and there is a very large vortex that the Fuel / air mixture formation positively influenced.

FIG. 6 shows a modified embodiment of the one in FIG. 5 shown vortex generator 9a, in which the two side surfaces 11 and 13 are not rectangular in shape Have triangles, but are trapezoidal. Also these vortex generators 9a are excellent for Vortex generation suitable.

Figures 7 to 10 show different arrangement variants the vortex generators 9 and 9a in the ring channel 20 of the premix burner.

In FIG. 7, vortex generators 9 according to FIG. 4 are both on the inner cylinder wall 21a, as well as on the outer cylinder wall 21b arranged. They have a height h that is almost the whole Fills channel height H.

In Fig. 8 are the vortex generators 9 that are on the inner Cylinder wall 21a are arranged smaller than that on the arranged outer wall 21b, its height h is only about H / 2, while the height h of the outer vortex generators 9 is equal to the channel height H. By using vortex generators 9 different geometries create vortices different strength, which is beneficial to flame stabilization necessary residual vertebrae.

9 shows an arrangement of vortex generators 9a with a 6. The height h corresponds to the channel height H, i.e. they fill the entire channel height H. The flattened part of the roof surface 13 is adjacent to the inner Cylinder wall 21a. The resulting eddies are with arrows characterized.

Finally, in FIG. 10 there is a variant of the arrangement of the vortex generators 9a shown in FIG. 5 in the ring channel 20. The vortex generators 9a are both on the inner cylinder wall 21a, and also arranged on the outer cylinder wall 21b, for example welded on. Two opposite Vortex generators 9a are each divided by half offset to each other in the circumferential direction, so that the twist direction Outside and inside is the same and the vertebrae are like add up to a large vortex that is both sufficient is for the complete mixing of air and fuel and then as a residual vortex for flame stabilization contributes.

The premix burner is also excellent for operation with Partial load suitable because it is due to the geometry of the burner is easily possible, pilot gas or secondary gas directly into the recirculation zone. This will limit the stability of the burner enlarged.

A possible risk of kickback exists in the case of the invention Burner not because high flow rates in prevail in the mixing zone and by choosing the one described above Vortex generator type no recirculation areas generated in the mixing zone. It is also easy possible with several premix burners according to the invention to operate an annular combustion chamber.

Reference list

1

Combustion air

2nd

fuel

3rd

pipeline

4th

Opening in pos. 21

5

Loop

6

Liquid fuel line

7

liquid fuel

8th

Deflector blade

9.9a

Vortex generator

10th

Roof area

11

Side surface

12th

Long edge

13

Side surface

14

Long edge

15

transverse edge of item 10

16

Connecting edge

17th

Edge of 19th

18th

top

19th

Interface

20th

Ring channel

21a, b

Cylinder wall

22

Recirculation zone

α

Arrow angle

β

Angle between the main flow direction and item 13

Θ

Angle of attack

H

Height of pos. 9, 9a

H

Height of item 20

L

Length of item 20

Claims (17)

1. Premix burner for the combustion of gaseous and/or liquid fuel, the premix burner working with a fuel-feed system, in which the fuel is injected as secondary flow into a gaseous, ducted main flow, the secondary flow having a substantially smaller mass flow than the main flow, the premix duct (20) through which flow occurs being annular and being defined by an inner (21a) and an outer cylinder wall (21b), which cylinder walls (21a, 21b) each have a constant radius along the length (L) of the duct (20), and the main flow being guided via vortex generators (9, 9a) which generate longitudinal vortices without a recirculation area and of which a plurality are arranged next to one another over the periphery of the annular duct (20) on at least one duct wall (21), and means for injecting fuel being arranged directly downstream of the vortex generators (9, 9a) on the inner and/or outer duct wall (21a, 21b), wherein

   the vortex generators (9, 9a) generate such vortices which leave behind a residual vortex after the complete mixing of the fuel with the air of the fuel/air mixture flow,

   the length (L) of the annular main flow duct (20) of constant height (H) and formed by the duct walls (21a, 21b) downstream of the vortex generators (9) and the fuel injection is in the region of 5 to 20 times its height (H), and

   the annular main flow duct (20) subsequently widens by closing the inner cylinder wall (21a) to form a circular main flow duct.
2. Premix burner according to Claim 1, characterized in that the main flow duct widens gradually.
3. Premix burner according to Claim 1, characterized in that the main flow duct widens abruptly.
4. Premix burner according to Claim 1, characterized in that

   a vortex generators [sic] (9) has three surfaces (10, 11, 12) around which flow occurs freely and which extend in the direction of flow and of which one forms the top surface (10) and the other two form the side surfaces (11, 13),

   in that the side surfaces (11, 13) are flush with the same duct wall (21) and one side surface (11) is provided with a half sweepback angle (α/2), whereas the other side surface (13) is straight and oriented in the direction of flow,

   in that the top surface (10), with an edge (15) running transversely to the duct (20) through which flow occurs, bears against the same duct wall (21) as the side surfaces (11, 13),

   and in that the longitudinally directed edges (12, 14) of the top surface (10), which are flush with the longitudinally directed edges of the side surfaces (11, 13) projecting into the flow duct (21) [sic], run at a setting angle () to the duct wall (21).
5. Premix burner according to Claim 4, characterized in that the two side surfaces (11, 13) enclose a connecting edge (16) with one another which together with the longitudinally directed edges (12, 14) of the top surface (10) forms a point (18), and in that the connecting edge runs in the radial line of the curved duct wall (21).
6. Premix burner according to Claim 4, characterized in that the connecting edge (16) and/or the longitudinally directed edges (12, 14) of the top surface are designed to be more or less sharp.
7. Premix burner according to Claim 6, characterized in that the connecting edge (16) forms the downstream edge of the vortex generator (9), and the edge (15) of the top surface (10) running transversely to the duct (20) through which flow occurs is the edge acted upon first by the main flow.
8. Premix burner according to Claim 1, characterized in that the vortex generators (9a) have approximately the shape of a right-angled triangle of small thickness, the two triangular side surfaces (11, 13) around which flow occurs run parallel to one another and enclose together with the top surface (10) the connecting surface (19), the top surface (10) with an edge (15) and the connecting surface (19) with an edge (17) bearing against the same duct wall as the two side walls (11, 13), and the side surfaces (11, 13) forming an angle (β) with the main flow direction of the incoming air.
9. Premix burner according to Claim 8, characterized in that the side surfaces (11, 13) of the vortex generators (9a) are of trapezoidal design.
10. Premix burner according to Claim 8, characterized in that the top surface (10) is designed to be convex or concave.
11. Premix burner according to Claim 8 or 9, characterized in that the connecting surface (19) forms the downstream surface of the vortex generator (9a), and the edge (15) of the top surface (10) running transversely to the duct (20) through which flow occurs is the edge acted upon first by the main flow.
12. Premix burner according to one of Claims 4, 8 or 9, characterized in that the height (h) of the vortex generator (9, 9a) corresponds to the height (H) of the duct (20).
13. Premix burner according to Claim 4 or 9, characterized in that an identical number of vortex generators (9, 9a) are arranged on the inner duct wall (21a) and on the outer duct wall (21b), in which case two opposite vortex generators (9, 9a) each are offset by half a pitch.
14. Premix burner according to Claim 4 or 9, characterized in that an identical number of vortex generators (9, 9a) are arranged on the inner duct wall (21a) and on the outer duct wall (21b), the inner and the outer vortex generators (9, 9a) having a different geometry.
15. Premix burner according to Claim 1, characterized in that gaseous fuel is fed via openings in the inner and/or outer duct wall (21a, 21b) downstream of the vortex generators (9, 9a).
16. Premix burner according to Claim 1, characterized in that liquid fuel is injected via a lance arranged downstream of the vortex generators (9, 9a).
17. Premix burner according to Claim 15 or 16, characterized in that additionally, liquid fuel is injected at the end of the inner cylinder.

Images