EP1802915B1 - Gas turbine burner - Google Patents

Description

Technical area

The invention relates to a premix burner for a gas turbine, in particular a nozzle for atomizing liquid fuel in a premix burner with a conical swirl generator and a subsequent cylindrical mixing section.

State of the art

Premix burners with a conical swirl generator and a subsequent cylindrical mixing section are made, for example EP 918191 known. The swirl generator, which serves as Vormischstrecke, has conical nested body part, the longitudinal axes are offset from each other. Compressed combustion air passes through tangential inflow channels between the walls of the conical body part into the mixing space of the swirl generator. A fuel is introduced via one or more nozzles or via fuel lines along the tangential Lufteinströmungskanäle in the mixing chamber and mixed there with the air. A further premixing of air and fuel is achieved in the subsequent mixing section by providing high mixing quality thanks to lossless flow guidance. The mixing section also fulfills the function of avoiding a flashback of the flame from the combustion chamber into which the mixing section opens.

Another premix burner of this type is in DE 103 55 930 disclosed. The outlet region of the mixing section is designed there with corrugations which generate axial vortices and thereby influence the turbulence in the outlet region and the flow stability. The fuel is introduced axially via a nozzle in the conical swirl generator, wherein the nozzle opening is located on the longitudinal axis of the premix burner.

DE 197 30 617 discloses a two-stage pressure atomizer nozzle for use in combustion engineering with two coaxial tubes and a mixing chamber into which two feed channels lead. A nozzle exit bore is located on the axis of the nozzle tubes and has a diameter in a given ratio to the diameter of the feed channels.

DE 44 40 558 discloses a premix burner with a conical swirl generator. The fuel is introduced via a nozzle with openings that are not on the longitudinal axis of the nozzle. The angle between the resulting spray cones and the longitudinal axis of the nozzle is in particular greater than the propagation angle of the conical part of the swirl generator. Said fuel nozzle is designed specifically for a premix burner without a cylindrical mixing section.

EP 899 508 discloses a premix burner having a swirl generator with a cylindrically formed mixing section as described above, and more particularly a fuel nozzle with nozzle tubes 104 each producing a fuel jet at an injection angle with respect to the central axis of the fuel nozzle equal to the angle of propagation of the swirl generator cone.

EP 902233 discloses a combined Druckzerstäuberdüse for a gas turbine burner with a swirler whose nozzle body has two separate feed channels, each of which leads an outlet opening into the mixing chamber of the burner. The nozzle body thus has two different nozzles, a radially outer multi-hole nozzle with decentralized outlet openings and a central, lying on the longitudinal axis nozzle with a centrally arranged outlet opening. The decentralized outlet openings are positioned so that the spray cones are directed into the wake of the conical shells of the swirl generator. This nozzle is operated at full load via the decentrally positioned outlet openings. At partial load, the nozzle is switched to the central outlets to avoid application of fuel oil droplets to the walls of the swirl generator.

DE 19536837 discloses an apparatus for injecting fuels with a swirl chamber within the injector or nozzle. An axially extending air supply channel 5 and a parallel to the longitudinal axis of the nozzle extending fuel channel 2 leads into this swirl chamber 1, are mixed in the air and fuel in a first phase already within the nozzle. The Swirl chamber has a conical constriction in the flow direction, through which the air-fuel mixture flows and finally passes through a lying on the longitudinal axis of the nozzle outlet opening in a burner mixing chamber. The single outlet opening from the nozzle is arranged on the longitudinal axis of the nozzle.

Presentation of the invention

• eine Tröpfchengrössenverteilung des zerstäubten Flüssigbrennstoffs erzielt wird, die eine vollständige Verdampfung der Tröpfchen ermöglicht, bevor es zur Verbrennung in der Brennkammer kommt,
• eine genügende Eindringtiefe der Brennstofftröpfchen im Mischraum des Vormischbrenners garantiert ist,
• durch die ersten zwei Eigenschaften tiefe Schadstoffemissionen, insbesondere von NO_x, erreicht werden,
• möglichst keine Tröpfchen an die Wände des Vormischbrenners gelangen.

It is the object of the cited prior art of the present invention, the task for a premix burner of the type mentioned with a conical swirl generator and subsequent cylindrical mixing section, which opens into a combustion chamber, and openings for air inflow along the conical parts of the swirl generator, a suitable high pressure To create atomizer nozzle. In particular, the nozzle is to be further developed in view of the cited prior art so that

• a droplet size distribution of the atomized liquid fuel is achieved which allows complete evaporation of the droplets before combustion in the combustion chamber occurs,
• a sufficient penetration depth of the fuel droplets is guaranteed in the mixing chamber of the premix burner,
• low pollutant emissions, in particular NO _x , can be achieved by the first two properties,
• if possible, do not allow any droplets to reach the walls of the premix burner.

For the abovementioned premix burner, a high-pressure atomizer nozzle according to the invention is proposed, which has one or more fuel channels for the supply of liquid fuel into an interior of the nozzle, wherein the liquid fuel is at full load under a pressure of more than 50 bar. The high-pressure atomizing nozzle has at least two outlet channels and openings through which the liquid fuel exits from a single interior space in the nozzle into the mixing space of the swirl generator, wherein the outlet channels are arranged with respect to the longitudinal axis of the nozzle decentralized, so that the exiting spray cone on the wake of the directed to individual cone shells. According to the invention, the outlet channels and openings of the nozzle are arranged and designed such that the spray cones emanating from the outlet openings have a longitudinal axis which is at an angle with respect to the nozzle Longitudinal axis of the swirl generator and the mixing path, which is smaller than the cone half-angle of the swirl generator.

The inventive arrangement of the outlet openings in said angular range affords the advantage that the fuel droplets do not reach the walls of the premix burner and coking of fuel oil droplets on the walls of the swirl generator is avoided. In addition, it is achieved that the fuel cone impinges at a shear angle on the incoming between the conical parts of the swirl generator air, which is small enough that the atomized fuel flow maintains a high speed, thereby achieving a high penetration depth in the premix burner and in the combustion chamber. On the other hand, an excessively large orientation angle of the spray cones relative to the longitudinal axis of the swirl generator would lead to the atomized fuel meeting the air inflow earlier and being guided by the air flow to the center of the swirl generator. The orientation of the outlet openings in said angle with respect to the longitudinal axis of the premix burner together with the high pressure of the fuel causes the second atomization, ie a very high degree of atomization, to be achieved on the first atomization at the nozzle exit, thereby achieving small droplet sizes and a rapid evaporation result. These features of atomization lead to a direct mixing of the fuel with the compressed air in the cone part of the premix burner and to a good homogeneous mixture with the compressed combustion air at the end of the mixing section. These features lead to a total of low Schademissionswerten.

In a preferred embodiment of the invention, the exit channels are oriented so that the longitudinal axes of the individual resulting spray cones extend at an angle with respect to the longitudinal axis of the swirl generator, which is smaller than the half angle of the conical shells and greater than 10 °. In a specific embodiment, this angle is in a range of 10 ° to 18 °.

A minimum value for this angle will cause the fuel spray cone to not reach too close to the center of the swirl generator. If the atomized fuel comes too close to the center, the pollutant emission values for the premix burner are higher.

In a further preferred embodiment, the nozzle has in its interior a supply channel for fuel, which leads into a single inner space of the nozzle.

This interior is connected via the at least two outlet channels with the interior of the swirl generator. The at least two outlet channels of the nozzle are preferably arranged with respect to the nozzle axis in the radially outer half with respect to the longitudinal axis of the nozzle. This causes less fuel to get into the center of the swirl generator. Conveniently, the openings are positioned symmetrically with respect to the longitudinal or central axis of the nozzle, so that an overall axis-symmetrical hollow spray cone is formed. The orientation of the individual spray cone is in turn at an angle smaller than the cone angle of the swirl generator.

In a further preferred embodiment of the invention, the high-pressure atomizer nozzle and in particular its outlet channels have a specific internal geometry, which contributes to the desired stability of the spray cone and penetration depths. For this purpose, the nozzle outlet channels, which lead from its interior through the nozzle wall into the interior of the swirl generator, wherein the outlet channels in the flow direction have a first cylindrical path, a conically formed constriction and finally a second cylindrical route. The constriction has a predetermined angle to the longitudinal axis of the outlet channel. Preferably, this half angle of the conical constriction is less than 45 °. The longitudinal axes of the outlet channels each extend at an angle to the longitudinal axis of the nozzle, which is smaller than the half angle of the conical parts of the swirl generator. The internal geometry of the exit channels provides the advantage of avoiding turbulence as well as cavitation effects.

The inventive high-pressure atomizer differs from the prior art, for example of EP 902233 in that the nozzle is formed greatly simplified overall. Its interior consists of a single inner chamber, which leads to reduced turbulence at the nozzle outlet and a more stable spray cone. It has only one set of outlets through which the liquid fuel is sprayed for all different operating situations and loads. For this purpose, however, the outlet openings have the specific internal geometry according to the invention and alignment with respect to the longitudinal axis of the premix burner.

In a first specific and preferred embodiment, the outlet channels consist of tubes, which from the interior of the nozzle through the wall and extend beyond the surface of the nozzle. In a first variant, the tubes have a length such that they only protrude beyond the surface of the nozzle, but are shorter than the nozzle tip. In another variant, they extend beyond the tip of the nozzle.

In a second specific embodiment, the outlet channels with said cylindrical sections and conical narrowing lead from the interior of the nozzle through the wall, wherein the outlet opening is located on the outer surface of the nozzle. In this embodiment, the outer wall of the nozzle tip is conically formed.

The internal geometry of the outlet channels and in particular the narrowing of a given angle in front of the outlet opening into the swirl generator causes a reduction of turbulence in the spray cone and a smaller spread angle of the spray cone. This allows a spray cone with a more uniform velocity profile. Finally, the increased flow stability in the spray cone allows improved placement of the fuel in the premix burner and thus improved flame conditions.

In a further embodiment, the second cylindrical sections of the outlet channels each have a length that is at most five times the diameter of the outlet openings. Such a length to diameter ratio contributes to an improvement in the airfoil and flow stability. In a specific embodiment, the outlet openings have a diameter of 0.5 - 1.5 mm.

In a further preferred embodiment of the invention, the outer wall of the nozzle tip is formed rounded together with the aforementioned internal geometries of the outlet channels of the nozzle, preferably oval in cross-section. The rounded shape provides further advantages in terms of the air inflow, in that the air flow of this shape can follow the outer wall of the nozzle uniformly and form correspondingly little vortex or recirculation downstream of the nozzle. This increases the homogeneity of the mixing of air and fuel, which causes a lowering of the NOx emission values.

Finally, a reduced recirculation downstream of the nozzle also influences the swirl at the end of the cylindrical mixing section and leads to an aerodynamic stabilization of the flame in the combustion chamber. Such Stabilization allows greater freedom in the operating parameters of the burner.

In a variant of the invention, the premix burner in the cylinder wall of the mixing section, which follows the swirl generator in the flow direction, further openings for the inlet of compressed air.

In a further variant, the premix burner has further air inlet channels, which run directly along the high-pressure atomizer nozzle and convey air into the mixing chamber of the swirl generator there. By this measure, a recirculation zone is formed only after the mixing section, which causes a further stabilization of the flame.

The high-pressure atomizing nozzle according to the invention is suitable not only for use in a premix burner with swirl generator with subsequent mixing section, but also for premixing with swirl generator alone without mixing section. In one application of this type, the high-pressure atomizer nozzle is arranged so that its tip protrudes up to half the length of the swirl generator or over half thereof.

Brief description of the drawings

• Figur 1 einen Längsschnitt durch einen Vormischbrenner mit einem kegelförmigen Drallerzeuger und darauffolgender Mischstrecke,
• Figur 2 einen Schnitt durch den Vormischbrenner und Düsenspitze gemäss II-II in Figur 1,
• Figur 3a einen Längsschnitt einer bevorzugten Ausführung der erfindungsgemässen Düse,
• Figur 3b eine Detailansicht der Innengeometrie der Düse von Figur 3a,
• Figur 3c eine Variante der Ausführung von Figur 3a
• Figur 4 einen Längsschnitt einer weiteren Ausführung der Hochdruck-Zerstäuberdüse und ihrer Innengeometrie,
• Figur 5 eine Anwendung der Düse in einem Vormischbrenner mit kegelförmigem Drallerzeuger ohne darauffolgende Mischstrecke.

Show it

• FIG. 1 a longitudinal section through a premix burner with a conical swirl generator and subsequent mixing section,
• FIG. 2 a section through the premix burner and nozzle tip according to II-II in FIG. 1 .
• FIG. 3a a longitudinal section of a preferred embodiment of the inventive nozzle,
• FIG. 3b a detailed view of the internal geometry of the nozzle of FIG. 3a .
• Figure 3c a variant of the execution of FIG. 3a
• FIG. 4 a longitudinal section of another embodiment of the high-pressure spray nozzle and its internal geometry,
• FIG. 5 an application of the nozzle in a premix burner with a conical swirl generator without subsequent mixing section.

Embodiment of the invention

FIG. 1 shows a premix burner, for example for a gas turbine. It has a conical swirl generator 1 and a subsequent cylindrical mixing section 2, which opens into a combustion chamber space 3. The swirl generator 1 consists in this example of four nested cone parts 4a, 4b, 4c, 4d, of which in FIG. 1 the conical parts 4b and 4d can be seen. The individual longitudinal axes of the conical parts are arranged offset from each other and from the longitudinal axis 5 of the swirl generator, as shown FIG. 2 removable. The conical parts 4a-d each extend at an angle α to the longitudinal axis 5 of the swirl generator 1. Together with their longitudinal edges, they form interspaces 6, which are used for introducing compressed combustion air whose flow profile is indicated by the arrows 7. At the outlet of the swirl generator 1 sheets 8 are arranged for the purpose of forming transition channels in the mixing section. 2
A high-pressure atomizing nozzle 10 is arranged to introduce liquid fuel into the swirl generator 1 in the initial part of the conical swirl generator. This is according to the following FIGS. 3a-c and FIG. 4 is formed so that an alignment of the spray cone 11 generated is achieved at an angle β with respect to the longitudinal axis 5 of the swirl generator, wherein the angle β is smaller than the angle α, or the half angle of the conical parts of the swirl generator. This orientation of the spray cone avoids wetting of the walls of the swirl generator by fuel oil droplets and coking of the walls. In the FIG. 1 Further openings 14 are arranged in the outer wall of the cylindrical mixing section 2 for supplying air into the mixing section. These cause a stabilization of the flame and avoid a flashback.

FIG. 2 shows in cross section II-II the swirl generator 1 with conical parts 4a-d and the centrally arranged on the longitudinal axis of the swirl generator high-pressure atomizer nozzle 10. Arrows 7 indicate the air inflow into the interior of the swirl generator. On the nozzle 10, positions 12a-d are indicated decentralized to the longitudinal axis of the fuel nozzle 10, at which fuel emerges. In the example shown, four opening positions are shown, for example, two or any more positions are possible. The outlet openings are positioned so that the exiting spray cone to the wake of the individual Tapered parts 4a-d is directed. For this purpose, the outlet openings are each arranged on auxiliary lines 13a-d, which run at a right angle to the tangent of the end portion of the conical shells 4a-d. This positioning of the outlet openings and spray cone causes the spray cones are detected by the incoming air flows 7 so that the sprayed fuel reaches a large penetration depth in the premix burner. On the other hand, a different positioning of the spray cones would cause the spray cones to be caught earlier by the air currents compared to the orientation shown and would be directed towards the center of the premix burner, leading to higher emission levels.
FIG. 3a shows a preferred high-pressure atomizer nozzle according to the invention with outer rounded tip 31 and an inner space 32 which has a conically shaped inner wall 33 towards the tip. From the interior space 32, two or more pipes 34 lead through the nozzle wall into the interior of the swirl generator, wherein the longitudinal axes 38 of the pipes 34 extend at an angle β to the longitudinal axis 5 of the nozzle and the swirl generator. In a first variant, the tubes 34 extend over a length such that they protrude beyond the tip of the nozzle. The outer wall of the end portions of the tubes are each preferably rounded.

FIG. 3b shows a second variant in which two or more tubes 34 'extend only just over the outer wall of the nozzle 10, so that they extend less far into the swirl generator than the nozzle tip itself.

In both variants, the nozzle tip is rounded. The flow of air introduced through inlet channels directly along the nozzle is positively affected by this type of nozzle tip in the region and subsequently the nozzle. In particular, air recirculations in the area of the nozzle and subsequently the nozzle are reduced, which improves the mixing of fuel and air and reduces the NO _x emission values.

Figure 3c shows in detail the internal geometry of the nozzle tubes 34. These have in an initial part on a leading away from the interior of the nozzle first cylindrical path 35. In the flow direction follows a conical, narrowing transition section 36 with a cone half-angle δ wall of the constriction with respect to the longitudinal axis 38 of the tube smaller than 45 °, which opens into a second, narrower cylindrical path 37 with a narrower diameter. The length of the second cylindrical section 37 is preferably at most five times the diameter of the outlet opening.

Another embodiment of the fuel atomizing nozzle 10 according to FIG. 4 has an inner space 20 which is tapered towards the end of the nozzle in the flow direction. From the conically formed tapered end wall 21 of the inner space 20, two or more outlet channels 22 each lead to a first cylindrical section 23, one conical narrowing 24 following in the flow direction and a second narrower cylindrical section 25 which finally leads to an outlet opening 26. The arrows indicate the flow direction of the liquid fuel. The longitudinal axes 27 of the exit channels, which are equal to the longitudinal axes of the resulting spray cones, extend at an angle β with respect to the longitudinal axis 5 of the nozzle and the swirl generator. The outlet openings 26 are arranged in particular in the radially outer half of the nozzle. Preferably, they have a diameter of 0.5 - 1.5 mm.
The nozzle tip 28 is externally conical in the embodiment shown.

FIG. 5 shows an application of the novel high-pressure atomizer in a premix burner with a conical swirl generator, wherein no mixing section follows the swirl generator, but the swirl generator opens directly into a combustion chamber. In particular, in this premix burner, the atomizer nozzle extends to half the length of the interior of the swirl generator or further. The nozzle has one of the embodiments with outlet channels according to the FIGS. 3a-c and 4 on.

LIST OF REFERENCE NUMBERS

1

swirl generator

2

mixing section

3

Interior combustion chamber

4a-4d

Cone parts swirl generator

5

Longitudinal axis swirl generator

6

Channels air inflow

7

airflow

8th

deflectors

10

High-pressure fuel nozzle

12a-d

Openings in nozzle tip

13a-d

Guides perpendicular to the tangent at the end of the cone shells

14

Air inlet openings in mixing section

20

Interior nozzle conical tip part

21

inner wall

22

outlet channel

23

first cylindrical route

24

Conical constriction

25

second cylindrical route

26

outlet opening

27

Longitudinal axis of the outlet channel and spray cone

28

conical nozzle tip

31

rounded nozzle tip

32

Interior nozzle

33

Inner walls nozzle

34.34 '

pipe

35

first cylindrical route

36

conical transition section

37

second cylindrical route

38

Longitudinal axis tube

40

partition wall

41

Tip part nozzle

42

Interior nozzle

43

Opening in partition

44

supply route

45

Openings in nozzle tip

Claims (16)

1. Premix burner with a swirl generator (1), consisting of cone shells (4a-4d) having a cone half-angle (α) and a mixing portion (2) downstream of the swirl generator (1) which opens into an interior (3) of a burner chamber, and with ducts (6) for the supply of compressed combustion air to the swirl generator (1), and with a high-pressure nozzle (10) for atomisation of liquid fuel with at least one fuel duct for supplying fuel to an interior (20, 32) of the high-pressure nozzle (10), wherein the high-pressure nozzle (10) comprises at least two outlet channels (22, 34, 34') which lead from the interior (20, 32) of the high-pressure nozzle (10) to the interior of the swirl generator (1) and are arranged decentrally relative to the longitudinal axis of the nozzle (10) and are oriented such that spray cones (11) emerging from the outlet channels (22, 34, 34') are directed at the wake of the individual cone shells,
   characterised in that
   the outlet channels (22, 34, 34') are configured such that the emerging spray cones (11) each have a longitudinal axis which runs at an angle (β) to the longitudinal axis (5) of the swirl generator which is smaller than the cone half-angle (α) of the swirl generator (1).
2. Premix burner according to claim 1, characterised in that the angle (β) between the longitudinal axes (26, 37) of the spray cone (11) and the longitudinal axis (5) of the swirl generator (1) is less than the cone half-angle (α) of the swirl generator (1) and greater than 10º.
3. Premix burner according to claim 1, characterised in that the angle (β) between the longitudinal axes (26, 37) of the spray cone (11) and the longitudinal axis (5) of the swirl generator (1) lies in a range between 10º and 18º.
4. Premix burner according to claim 1, characterised in that the two or more outlet openings (24, 25, 34, 34') for atomisation of the fuel are arranged in the radially outer half of the high-pressure nozzle (10) relative to the longitudinal axis of the high-pressure nozzle (10), and rotationally symmetrically relative to the longitudinal axis (5) of the high-pressure nozzle (10).
5. Premix burner according to any of the preceding claims, characterised in that in the flow direction of the liquid fuel, the outlet channels (22, 34, 34') have a first cylindrical portion (23, 35), a conical taper (24, 36) and a second cylindrical portion (25, 37).
6. Premix burner according to claim 5, characterised in that the outlet channels comprise pipes (34) which protrude beyond the tip of the high-pressure nozzle (10).
7. Premix burner according to claim 5, characterised in that the outlet channels comprise pipes (34') which protrude beyond the outer surface of the high-pressure nozzle (10), wherein the tip of the high-pressure nozzle (10) protrudes further into the swirl generator than the pipes (34').
8. Premix burner according to claim 5, characterised in that a half-angle (δ) of the conical taper (36) between the wall of the conical portion (36) and the longitudinal axis (38) of the outlet channels (34, 34') is less than 45º.
9. Premix burner according to claim 5, characterised in that each second cylindrical portion (25) leads to an outlet opening (26) on the outer surface of the high-pressure nozzle (10).
10. Premix burner according to claim 5, characterised in that the conical taper (24) has a cone half-angle in the range from 30º to 45º.
11. Premix burner according to any of claims 6 - 10, characterised in that the tip of the high-pressure nozzle (10) is formed rounded.
12. Premix burner according to any of claims 6 - 10, characterised in that the tip of the high-pressure nozzle (10) is formed conical.
13. Premix burner according to any of claims 5 - 10, characterised in that the length of the second cylindrical portions (25, 37) in each case amounts to maximum of five times the diameter of the outlet openings.
14. Premix burner according to any of claims 1 - 13, characterised in that the outlet openings (25) of the outlet channels have a diameter in a range from 0.5 to 1.5 mm.
15. Premix burner according to any of the preceding claims, characterised in that in the outer wall of the cylindrical mixing portion (2), the premix burner has openings (14) for the inlet of compressed air.
16. Premix burner with a swirl generator (1) consisting of cone shells having a cone half-angle (α), which opens into an interior of a burner chamber, and with ducts for the supply of compressed combustion air to the swirl generator, and with a high-pressure nozzle (10) for atomisation of liquid fuel with one or more fuel ducts for supplying fuel to an interior (20, 32) of the high-pressure nozzle (10), and the high-pressure nozzle (10) comprises at least two outlet channels (22, 34, 34') for atomisation of the fuel which lead from the interior (20, 32) of the high-pressure nozzle (10) to the interior of the swirl generator and are arranged decentrally relative to the longitudinal axis of the nozzle (10),
    characterised in that
    the outlet channels (22, 34, 34') are configured such that spray cones (11) emerging from the outlet channels have a longitudinal axis which runs at an angle (β) to the longitudinal axis (5) of the swirl generator which is less than the cone half-angle (α) of the swirl generator (1),
    and in the flow direction of the liquid fuel, the outlet channels (22, 34, 34') have a first cylindrical portion (23, 35), a conical taper (24, 36) and a second cylindrical portion (25, 37),
    and the tip of the high-pressure nozzle (10) extends to half the length of the interior of the swirl generator or beyond the half.

Images