EP0711953A2 - Premix burner - Google Patents

Abstract

The burner has nozzle holes (18) in high air speed zones of the burner in two part conical bodies. The nozzle holes (18) connect the interior (14) of the burner and the nozzle body's inflow duct (24) for the liquid fuel (12) being atomised. The burner consists of at least two hollow conical part bodies (1,2). The narrowest cross-section of the conical interior formed by the conical part bodies contains a high pressure atomising nozzle (3) for liquid fuel. The nozzle holes point towards the air inlet slots (19,20) in the conical part bodies, in the burner. The angle ( beta ) between the fuel drop spray (4) and the burner's longitudinal axis (5) is at least as big as the half-cone angle ( alpha ) between the part cone bodies (1,2) and the burner's longitudinal axis.

Description

Technical field

The invention relates to a low-pollutant premix burner of the double-cone type for operating an internal combustion engine, a combustion chamber of a gas turbine group or firing system with a high-pressure atomization nozzle arranged in the tip of the cone cavity for atomizing liquid fuel, the nozzle being designed with or without turbulence chamber and having at least two nozzle bores with the Interior of the burner communicates.

State of the art

Atomizer burners are known in which the oil which is burned is finely divided mechanically. It is broken down into fine droplets of approximately 10 to 400 µm in diameter (oil mist), which evaporate and burn in the flame when mixed with the combustion air. In pressure atomizers (see Lueger - Lexikon der Technik, Deutsche Verlags-Anstalt Stuttgart, 1965, Volume 7, p.600), the oil is supplied to an atomizing nozzle by an oil pump at a pressure of approx. 4 to 25 bar. The oil enters a swirl chamber via essentially tangential slots and leaves the nozzle via a nozzle bore. It is thereby achieved that the oil particles receive two components of motion, an axial and a radial. The as a rotating hollow cylinder from the Oil film emerging from the nozzle bore expands due to the centrifugal force into a hollow cone, the edges of which get into unstable vibrations and tear into small oil droplets. The atomized oil forms a cone with a more or less large opening angle.

• 1. Die Tröpfchengrösse muss gering sein, damit die Öltröpfchen vor der Verbrennung vollständig verdampfen können.
• 2. Der Öffnungswinkel (Ausbreitungswinkel) des Ölnebels soll klein sein.
• 3. Die Tropfen müssen eine hohe Geschwindigkeit und einen hohen Impuls haben, um weit genug in den verdichteten Verbrennungsluftmassenstrom eindringen zu können, damit sich der Brennstoffdampf vollständig mit der Verbrennungsluft vor Erreichen der Flammenfront vormischen kann.

In the low-pollutant combustion of mineral fuels in modern burners, for example in premix burners of the double-cone type, which are described in their basic structure in EP 0321 809 B1, special requirements are placed on the atomization of the liquid fuel. The main ones are:

• 1. The droplet size must be small so that the oil droplets can evaporate completely before combustion.
• 2. The opening angle (angle of spread) of the oil mist should be small.
• 3. The drops must have a high speed and a high momentum in order to be able to penetrate far enough into the compressed combustion air mass flow so that the fuel vapor can completely premix with the combustion air before reaching the flame front.

Swirl nozzles (pressure atomizers) and air-assisted atomizers of the known types with a pressure of up to approx. 100 bar are hardly suitable for this because they do not allow a small angle of spread, the atomization quality is limited and the impulse of the drop spray is low.

As a result of this insufficient evaporation and premixing of the fuel, it is necessary to add water to lower the flame temperature and thus NOx formation. Since the water supplied often disturbs flame zones, which in themselves do not generate much NOx, but are very important for flame stability, instabilities such as flame pulsation often occur and / or poor burnout, which leads to an increase in CO emissions.

An improvement can be achieved with the high pressure atomizing nozzle disclosed in EP 0 496 016 A1. This consists of a nozzle body, in which a turbulence chamber is formed, which is connected to an outside space via at least one nozzle bore, and which has at least one supply channel for the liquid to be atomized, which can be supplied under pressure. It is characterized in that the cross-sectional area of the feed channel opening into the turbulence chamber is larger by a factor of 2 to 10 than the cross-sectional area of the nozzle bore. This arrangement makes it possible to generate a high level of turbulence in the turbulence chamber, which does not subside on the way to the point of exit from the nozzle. The fluid jet is caused to decay rapidly by the turbulence generated in front of the nozzle bore in the outside space, that is to say after leaving the nozzle bore, resulting in low angles of propagation of 20 ° and less. The droplet size is also very small. The only disadvantage is the loss of fuel pulse in the turbulence generator, which does not allow directed introduction.

Presentation of the invention

The invention tries to avoid all these disadvantages. It is based on the task of creating a low-pollutant premix burner of the double-cone type, which has a high-pressure atomizing nozzle for atomizing liquid fuel, which is of simple construction and with which a very good atomization quality with a high fuel pulse is achieved.

According to the invention, this becomes thereby in a premix burner of the double cone type according to the preamble of patent claim 1 achieved that the nozzle outlet bores of the high pressure atomizing nozzle are aligned with the zones of high air velocity and the angle of the fuel spray to the axis of the burner is at least as large as the cone half angle of the burner.

The advantages of the invention include in the fact that in the high-pressure atomization nozzle according to the invention, a fine atomization of the fuel is associated with a high fuel pulse and thus rapid evaporation of the fuel and good premixing of the fuel spray with the combustion air are achieved. The high-pressure atomizing nozzle is simple in design, easily accessible inside the burner and is characterized by a small space requirement in the tip of the burner. The fuel can be injected specifically into zones of high air speed. The need to add water to reduce NOx emissions is eliminated, because due to the above fine atomization, rapid evaporation of the fuel and the good premixing of the fuel spray with the combustion air, the NOx emissions are very low.

It is particularly expedient if the nozzle bores of the high-pressure atomization nozzle are aligned with the air inlet slots of the conical partial bodies, because in this case the premixing of the fuel spray with the incoming combustion air is most intensive.

It is also advantageous if the high-pressure atomization nozzle is a turbulence-assisted high-pressure nozzle with a turbulence chamber arranged in front of the nozzle bores, the turbulence chamber being delimited by a tube, a conical cover of the tube in which the nozzle bores are arranged, and by a filler with at least one feed opening , which is preferably arranged centrally in the filler. The turbulence generated in front of the nozzle bore causes a rapid disintegration of the liquid jet and a particularly fine drop spray achieved. The resulting drop spray is also characterized by small spreading angles.

Finally, a high-pressure orifice nozzle is advantageously used as the high-pressure atomizing nozzle, which consists of a tube and a conical cover of the tube in which the nozzle openings are arranged. In this case, a very high fuel pulse is achieved, which enables the fuel spray to penetrate deeply into the combustion air.

It is also advantageous if the nozzle bores are arranged in the outer third of the conical cover near the wall of the tube. Then very good atomization qualities are achieved.

Brief description of the drawing

The drawing shows two exemplary embodiments of the invention using a double-cone burner for operating a gas turbine.

Fig. 1

eine schematische Ansicht eines Doppelkegelbrenners;

Fig. 2

einen Brenner gemäss Fig. 1 in perspektivischer Darstellung;

Fig. 3

einen vereinfacht dargestellten Schnitt in der Ebene III-III gemäss Fig. 2;

Fig. 4

einen vereinfacht dargestellten Schnitt in der Ebene IV-IV gemäss Fig. 2;

Fig. 5

einen vereinfacht dargestellten Schnitt in der Ebene V-V gemäss Fig. 2;

Fig. 6

einen Längsschnitt der turbulenzunterstützten Hochdruckzerstäubungsdüse in der Ebene der Düsenbohrungen;

Fig. 7

einen Längsschnitt der Hochdruck-Blendendüse in der Ebene der Düsenbohrungen;

Fig. 8

ein Diagramm zur Veranschaulichung der Abhängigkeit der Tropfengrösse vom Druck einer Hochdruckzerstäubungsdüse gemäss Fig. 6 bzw. 7;

Fig. 9

ein Diagramm zur Veranschaulichung der Abhängigkeit der Nox-Emissionen von der Flammentemperatur des Doppelkegelbrenners für verschiedene Düsen.

Show it:

Fig. 1

a schematic view of a double-cone burner;

Fig. 2

a burner according to Figure 1 in a perspective view.

Fig. 3

a simplified section in the plane III-III of FIG. 2;

Fig. 4

a simplified section in the plane IV-IV of FIG. 2;

Fig. 5

a simplified section in the plane VV of FIG. 2;

Fig. 6

a longitudinal section of the turbulence-assisted high-pressure atomization nozzle in the plane of the nozzle bores;

Fig. 7

a longitudinal section of the high-pressure orifice nozzle in the plane of the nozzle bores;

Fig. 8

a diagram to illustrate the dependence of the droplet size on the pressure of a high pressure atomizing nozzle according to Fig. 6 and 7;

Fig. 9

a diagram illustrating the dependence of the NOx emissions on the flame temperature of the double-cone burner for different nozzles.

Only the elements essential for understanding the invention are shown. The direction of flow of the media is indicated by arrows.

Way of carrying out the invention

The invention is explained in more detail below on the basis of exemplary embodiments and FIGS. 1 to 9.

1 schematically shows a section through the premix burner, which essentially consists of two partial cone bodies 1, 2 and whose basic structure is described in EP 0 321 809 B1. For a better understanding of the burner structure, it is advantageous if FIG. 2 and the sections shown in FIGS. 3 to 5 are used at the same time.

Fig. 2 shows a perspective view of the double-cone burner with integrated premixing zone. The two partial cone bodies 1, 2 are arranged radially offset from one another with respect to their longitudinal symmetry axes 1b, 2b. This creates tangential air inlet slots on both sides of the partial cone bodies 1, 2 in the opposite inflow arrangement 19, 20, through which the combustion air 15 flows into the interior 14 of the burner, ie into the cone cavity formed by the two partial cone bodies 1, 2. The partial cone bodies 1, 2 expand in a straight line in the direction of flow, ie they have a constant angle α with the burner axis 5. The two partial cone bodies 1, 2 each have a cylindrical starting part 1a, 2a, which also run offset. In this cylindrical starting part 1a, 2a there is a high-pressure atomization nozzle 3 with at least two nozzle openings 11, which are arranged approximately in the narrowest cross section of the conical interior 14 of the burner. Of course, the burner can also be designed without a cylindrical initial part, that is to say purely conical.

The two partial cone bodies 1, 2 each have a fuel feed line 8, 9 along the air inlet slots 19, 20, which are provided on the long side with openings 17 through which another fuel 13 (gaseous or liquid) flows. This fuel 13 is mixed with the combustion air 15 flowing through the tangential air inlet slots 19, 20 into the interior of the burner, which is represented by the arrows 16. Mixed operation of the burner via the nozzle 3 and the fuel feeds 8, 9 is possible.

On the combustion chamber side, a front plate 10 is arranged with openings 11, through which dilution air or cooling air can be supplied to the combustion chamber 22 if necessary. In addition, this air supply ensures that flame stabilization takes place at the burner outlet. There is a stable flame front 7 with a backflow zone 6.

The arrangement of guide plates 21 a, 21 b can be seen from FIGS. 3 to 5. These can be opened or closed, for example, about a pivot point 23, so that the original gap size of the tangential air inlet slots is thereby 19, 20 is changed. Of course, the burner can also be operated without these baffles 21a, 21b.

FIG. 6 shows a turbulence-assisted high-pressure atomization nozzle 3, which, as shown in FIG. 1 or FIG. 2, is arranged in the cone tip of the burner. It consists of a tube 26 which surrounds a feed channel 24 and a turbulence chamber 25. The tube 26 is closed by a conical cover 27 in which there are two nozzle bores 18 in the outer third near the tube wall. These nozzle bores 18 establish the connection between the turbulence chamber 25 located in the tube 26 and the interior 14 (cone cavity) of the burner. The turbulence chamber 25 is delimited next to the pipe 26 by a filler 28 and the cover 27 of the pipe 26. In the filler 28, a feed opening 29 for the fuel 12 to be atomized is arranged in the center. This opening can of course also be arranged off-center or there can be a plurality of feed openings 29. It is advantageous if the feed opening 29 has a cross section which narrows in the direction of flow, as shown in FIG. 6.

The fuel 12 to be atomized flows under a pressure of greater than 100 bar via the feed line 24 and the opening 29 into the turbulence chamber 25, which has an abruptly widening cross section with respect to the feed opening 29. The fuel jet hits the cone tip of the conical lid 27. A high level of turbulence is generated by intensive shearing and the rebounding of the jets from the surface of the lid, which does not subside on the short path until it emerges from the nozzle. The fluid jet is brought to rapid decay by the turbulence in the burner interior 14 generated in front of the two nozzle bores 18, which results in very small angles of propagation.

The fuel 12 is atomized well by the high momentum and the high relative speed to the air. It has a high penetration depth and thus leads to a high level of mixing.

The alignment of the nozzle bores 18 to the tangential air inlet slots 19, 20, that is to say to zones of very high air velocity, leads to a direct mixing in of the fuel 12 present in the form of a finely distributed drop spray 4. The fuel is distributed very well in the combustion air stream 15 along the burner wall. It mixes very well along the cone in the fresh air flow at the end of the burner, so that an excellent premixing is achieved, which has a favorable effect on a low value of the pollutant emissions.

Fig. 7 shows a second embodiment. Here, the high-pressure atomizing nozzle 3 is a multi-hole high-pressure orifice nozzle, the structure of which is the same as the above. corresponds to turbulence-assisted nozzle, although of course there is no turbulence chamber in the orifice nozzle. This means that in this case the achievable fuel drop size is somewhat larger under comparable conditions to the first exemplary embodiment (see Fig. 8), but a high fuel pulse can be achieved for this, which also results in the above-mentioned through the targeted injection into zones of high air speed. Advantages leads.

The cross section of the nozzle 3, its position and the direction of injection result from the desired throughput (depending on the form) taking into account sufficiently high Reynolds numbers in the nozzle bores 18.

For a turbulence-assisted pressure atomization nozzle, the diagram shown in FIG. 8 illustrates the dependence of the droplet diameter d _T on the admission pressure p for various Limit diameter of the drop mass distribution. Dx denotes the limit diameter that x mass% of all particles fall below. SMD is the Sauter diameter, i.e. the diameter of a droplet that has the same surface to volume ratio as the total jet. The high pressure atomization nozzle on which the diagram is based was charged with water and had the following parameters: Diameter of the nozzle 10.0 mm Feed channel diameter 8.0 mm Diameter of the feed opening in the filler 1.8 mm Diameter of the nozzle bores 0.6 mm Length of the turbulence chamber 7.0 mm.

FIG. 9 shows the dependence of the atmospheric NOx emission values on the flame temperature and the type of nozzle used for atomizing the liquid fuel. Turbulence-assisted two-hole high-pressure nozzles with different angles β between the fuel injection and the burner axis were examined (11 °, 15 °, 20 °). The cone half angle α of the burner was 10.95 ° in each case. In comparison to pressure atomizing nozzles (swirl nozzles), when using the high pressure atomizing nozzles 3 according to the invention with two nozzle bores 18 directed towards the air inlet slots 19, 20, premix burners of the double-cone type achieve significantly lower NOx emission values.

Reference list

1, 2

Partial cone body

1a, 2a

cylindrical starting part

1b, 2b

Central axis of the partial cone body

3rd

High pressure atomization nozzle

4th

Fuel drop spray

5

Burner axis

6

Backflow zone (vortex breakdown)

7

Flame front

8, 9

Fuel supply

10th

Front panel

11

Openings in the front panel

12th

liquid fuel

13

additional fuel (liquid or gaseous)

14

Interior of the burner

15

Combustion air flow

16

Injection fuel

17th

openings

18th

Nozzle bore

19, 20

tangential air inlet slot

21a, 21b

Baffle

22

Combustion chamber downstream of the burner

23

pivot point

24th

Feed channel

25th

Turbulence chamber

26

pipe

27

Cover of the pipe

28

Filling piece

29

Feed opening in the filler

α

Cone half angle

β

Angle between the drop spray and the longitudinal axis of the burner

d _T

Drop diameter

p

print

Dx

Limit diameter that x mass% of all particles fall below

SMD

Sauter diameter

Claims (6)

Premixing burner of the double-cone type for operating an internal combustion engine, a combustion chamber of a gas turbine group or firing system, the burner essentially consisting of at least two hollow conical partial bodies (1, 2) positioned one on top of the other in the flow direction with a cone half angle (α) constant in the flow direction, the longitudinal symmetry axes ( 1a, 1b) run radially offset from one another, resulting in tangential air inlet slots (19, 20) for a combustion air flow (15), the narrowest cross section of the conical cavity (14) formed by the conical partial body (1, 2) being a nozzle (3 ) is arranged for atomizing a liquid fuel (12) and the fuel injection forms an acute angle (β) with the longitudinal axis of the burner (5), and in the area of the air inlet slots (19, 20) the conical partial bodies (1, 2) or without means (8, 9, 17) for teaching a wide Ren liquid or gaseous fuel (13) are supplemented, and the nozzle is a high-pressure atomizing nozzle (3), which consists of a nozzle body in which at least one supply channel (24) for the atomized and can be supplied under a pressure of greater than 100 bar liquid fuel (12) is arranged and this feed channel (24) with or without a turbulence chamber (25) arranged therebetween is connected to the interior (14) of the burner via at least two nozzle bores (18), characterized in that the nozzle bores (18) on the Zones of high air velocity in the burner are aligned and the angle (β) between the fuel drop spray (4) and the longitudinal axis (5) of the burner is at least as large as the cone half angle (α) between the partial cone bodies (1, 2) and the longitudinal axis (5) of the burner. Premix burner according to Claim 1, characterized in that the nozzle bores (18) of the high-pressure atomization nozzle (3) are aligned with the air inlet slots (19, 20) of the conical partial bodies (1, 2). Premix burner according to claim 1, characterized in that the high-pressure atomization nozzle (3) is a turbulence-assisted high-pressure nozzle with a turbulence chamber (25) arranged in the flow direction in front of the nozzle bores (18), the turbulence chamber (25) being delimited by a tube (26), one conical cover (27) of the tube (26), in which the nozzle bores (18) are arranged, and of a filler (28) with at least one feed opening (29). Premix burner according to claim 1, characterized in that the high-pressure atomization nozzle (3) is a high-pressure orifice nozzle which consists of a tube (26) and a conical cover (27) of the tube (26) in which the nozzle openings (18) are arranged, consists. Premix burner according to claim 3 or 4, characterized in that the nozzle bores (18) are arranged in the outer third of the conical cover (27) near the wall of the tube (26). Premix burner according to claim 3, characterized in that the feed opening (29) is arranged centrally in the filler (28).

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