EP0911583A1 - Method of operating a premix burner - Google Patents

Abstract

At least a fuel in liquid form (2) in a full jet is atomized at an injection angle (alpha) of less than 10 degrees in the inner chamber (9) of the pre-mix burner (4). Radially outside and concentric to the at least one liquid fuel a screen air current is introduced into the inner chamber. Its introduction is at a low mass and its speed is at 5 to 60 m/s.

Description

Technical field

The invention relates to a method for operating a premix burner according to the preamble of claim 1 and a corresponding premix burner to carry out the procedure.

State of the art

Combustion chambers have long been available for stationary gas turbines in power plants with pre-mix burners designed as so-called double-cone burners proven, where the fuel from the outside by insertable fuel lances is fed. The lance is usually designed as a two-fuel lance, i.e. optionally gaseous fuel, e.g. Pilot gas, and / or more liquid Fuel, for example an oil-water mixture, are supplied. To are in the lance a liquid fuel pipe, an atomizing air pipe and a pilot gas pipe arranged concentrically. The tubes each form a channel for the Liquid fuel, the atomizing air and the pilot gas, which in at the lance head end of a central fuel nozzle. The fuel lance is stuck with its lance head in a corresponding inner tube of the double-cone burner, so that the escaping fuel in the middle of the burner interior connected to the inner tube arrives (see DE 43 06 956 A1).

A double cone burner is also known from EP 03 21 809 B1, which is used for intended for use in a combustion chamber connected to a gas turbine is. This burner consists of two hollow, complementary to the double cone burner Partial bodies that are arranged radially offset from one another. He owns one with a hollow cone-shaped interior enlarging in the direction of flow tangential air inlet slots. The fuel supply for the double-cone burner takes place from the outside via the fuel lance, which goes into the central liquid fuel nozzle flows. The latter forms a hollow cone-shaped Fuel spray consisting of liquid fuel and air, in which most fuel droplets at the outer end of the conical spray pattern are concentrated.

Because of the large injection angle of approx. 30 ° and the lack of an axial one Impulse at the center, these sprays are very sensitive to centrifugal forces generated by the vortex flow inside the burner. This will the fuel droplets are carried out relatively quickly centrifugally, which at the impact of a not insignificant amount under certain operating conditions of liquid fuel on the inner walls of the burner.

To atomize liquid fuels, so-called Full jet atomizers used, which form a conical full jet evenly generate distributed fuel droplets. Such a solution is from the Textbook "Atomization and sprays", by A. Lefebvre, West Lafayette, Indiana 1989, pp. 106/107, 238-241. With this atomizer nozzle, the liquid Fuel from an antechamber through a small, circular injection opening certain guide length ejected under high pressure. Generated thereby the full jet atomizer has a fuel jet with an injection angle of approximately 5 ° to 15 °.

Because of this small injection angle and the associated, only further Such full jet atomizers are used downstream with pre-mix burners equipped combustion chambers of gas turbine plants, however not used because the liquid fuel is atomized quickly shall be. In addition, the described full jet atomizer is for many combustion applications not very suitable because it tends to drop the fuel to concentrate in a small area immediately downstream of the nozzle. Especially under the unfavorable conditions of a low air / fuel ratio and at low air speed, atomization cannot be sufficient be achieved.

Presentation of the invention

The invention has for its object a method for operating a premix burner to create which is improved in certain operating modes Has functional reliability and functionality. In addition, a corresponding Premix burners to carry out the process can be specified.

According to the invention, this is achieved by using an operating method a premix burner designed according to the preamble of claim 1, at least one liquid fuel in a full jet and with an injection angle α injected into the interior of the premix burner of less than 10 ° becomes.

For this purpose, the liquid fuel nozzle is provided with a simple injection opening, which has a guide length I and a diameter d. The one through the Injection opening axially injected liquid fuel into the interior of the premix burner forms a full jet due to the influence of the opening Injection angle is less than 10 ° and is therefore relatively small. The act Fuel jet and the combustion air flow inside the premix burner together. Mainly due to the shear forces between the fuel jet and the swirled combustion air, is in the downstream area the premix burner achieves good atomization, resulting in combustion suitable, fine droplets are generated. Because of the small injection angle and the concentration of the axial pulse of the injected fuel in the burner axis, the influence of the swirl flow on the fuel droplets significantly reduced. The latter are from the centrifugal force Center carried away and mostly mixed with the combustion air. In addition the fuel droplets evaporate before they reach the burner walls to reach. In this way, the full jet can largely the premix burner penetrate without the fuel droplets wetting the burner walls. Despite significantly poorer atomization quality than conventional ones Liquid fuel nozzles, there is sufficient atomization, but none there is a significant increase in pollutant emissions.

The liquid fuel nozzle used is particularly simple, robust and reliable, which also helps to reduce costs. Your main parameters are the diameter d, the guide length l and the shape of the injection opening. The degree of turbulence is also decisive for the atomization Fuel flow, which is mainly due to the conditions upstream Injection opening and defined by the aforementioned axial guide length is.

The injection opening particularly advantageously has a ratio of the guide length to the diameter of 4 ≤ l / d ≤ 6. In the textbook "Atomization and sprays "by A. Lefebvre, West Lafayette, Indiana 1989, pp. 155-161, In particular in Fig. 5.4., which results are shown on the basis of test results Influence the ratio of the guide length to the diameter of the injection opening on the injection coefficient, i.e. on the ratio of the current to the theoretical flow rate through the injection opening. In doing so Quotients l / d examined up to 10 and found that the greatest injection coefficient is reached with a quotient l / d of approx. 2. In contrast to this The premix burner according to the invention with a liquid fuel nozzle became the doctrine equipped, the injection opening a ratio of the Guide length to the diameter with 4 ≤ l / d ≤ 6 and thus a injection coefficient has the consequence, which is clearly below the maximum. Nevertheless was able to use such a liquid fuel nozzle in one Premix burner a compact liquid fuel spray with the desired Injection angle and the required pulse can be achieved.

Because of this compact liquid fuel spray is in such an atomizer nozzle or an appropriately equipped premix burner on the burner head there is no fully prepared fuel mixture yet. Therefore, a pulsation-free operation over a wide load range and also with different ones Amount of water reached. The compact liquid fuel spray also hits not on the burner walls, causing the premix burner to overheat and the combustion chamber can be prevented as well as coking inside of the premix burner. Another that is focused exclusively on within the liquid fuel spray located in the combustion air flow The advantage is the good ignition and partial load capability without an additional injection stage. As a result, both the fuel lance and the driving concept are the entire combustion chamber easier and cheaper. After all, that too Retrofitting existing premix burners possible with minimal costs.

It is particularly advantageous outside and concentrically to the liquid fuel an umbrella air flow with a low mass into the interior of the premix burner introduced. For this purpose, the fuel lance consists of a central liquid fuel pipe, which is coaxially surrounded by an air tube. Because the liquid Full jet in this process or through the corresponding device is surrounded by an air flow, the liquid fuel spray remains small Mass flow in the center of the burner interior. So that is stability of liquid fuel, especially at low liquid flow rates, i.e. improved in ignition and partial load of the gas turbine, both improved ignition performance and higher part-load combustion performance become. With large liquid flow rates, however, the dominates Liquid flow. In addition, the injection opening and the area of the Burner head by the air flow against fuel deposits and consequently protected against coking.

It is particularly useful if the screen airflow is at a speed from 5 to 60 m / s and with a mass of 0.1 to 2.0% of the total air mass flow is injected into the interior of the premix burner.

In contrast to the known solutions of the prior art, this serves Shield air flow not for atomizing the liquid fuel, which is about 5 to 10% of the total air mass flow would be required. Rather, it will Small amount of axially injected air to control the aerodynamics in the area near the injection port, i.e. to improve the flow conditions of the Premix burner used. On the one hand, the air prevents that from Cross-sectional jump downstream of the injection opening caused suction of the Liquid jet on the inner wall of the premix burner and on the other one local twist count too high. The air flow also increases axial penetration of the full jet of liquid emerging from the liquid fuel nozzle. thats why the latter more stable with respect to the burner vortex or its centrifugal forces, what the inclination of the fuel droplets on the inner wall of the premix burner encountered, further decreased. When using pilot gas you can also whose feed slots / openings are protected against coking by means of the screen air flow become.

In a further embodiment of the invention, it is located in the interior of the premix burner, full jet of one spreading in the flow direction rotating combustion air stream flowing tangentially into the burner. The ignition of the combustion mixture that takes place takes place in the Area of the burner orifice, the flame in this area by a Backflow zone is stabilized. For this purpose, the premix burner consists of at least two hollow partial cone bodies arranged radially offset from each other, with a hollow cone-shaped interior that increases in the direction of flow.

The burner has tangential air inlet slots and the liquid fuel nozzle is connected to a fuel lance used to supply fuel.

In particular, this method provides a form of liquid spray with a small injection angle, which with the small opening angle of the premix burner interacts optimally. This creates ideal conditions for the Combustion of liquid fuel by means of a premix burner designed in this way created.

Brief description of the drawing

In the drawing, two exemplary embodiments of the invention are shown in FIG the premix burner used in the combustion chamber of a gas turbine system represented a liquid fuel nozzle according to the invention.

Fig. 1

einen Längsschnitt des Vormischbrenners;

Fig. 2

einen Schnitt durch den Vormischbrenner entlang der Pfeile II-II in Fig. 1;

Fig. 3

einen vergrösserten Ausschnitt der Fig. 1, im Bereich der Flüssigbrennstoffdüse

Fig. 4

die mit einer Flüssigbrennstoffdüse ausgestattete Brennstofflanze, in einem zweiten Ausführungsbeispiel;

Fig. 5

einen Längsschnitt des Vormischbrenners, mit der entsprechend Fig. 4 ausgebildeten Flüssigbrennstoffdüse.

Show it:

Fig. 1

a longitudinal section of the premix burner;

Fig. 2

a section through the premix burner along the arrows II-II in Fig. 1;

Fig. 3

an enlarged section of FIG. 1, in the area of the liquid fuel nozzle

Fig. 4

the fuel lance equipped with a liquid fuel nozzle, in a second embodiment;

Fig. 5

a longitudinal section of the premix burner, with the liquid fuel nozzle designed according to FIG. 4.

Only the elements essential for understanding the invention are shown. The gas turbine system, for example, does not show the compressor and the gas turbine. The direction of flow of the work equipment is indicated by arrows.

Way of carrying out the invention

The gas turbine system, not shown, consists of a compressor, one Gas turbine and a combustion chamber 1. In the combustion chamber 1 there are several both for operation with liquid fuel 2 as well as with gaseous fuel 3 suitable and designed as a double-cone pre-mix burner 4. The double cone burners 4 each consist of two half, hollow partial cone bodies 5, 6, each with an inner wall 7, 8. Close both inner walls 7, 8 a hollow cone-shaped interior 9 that increases in the flow direction a (Fig. 1). The partial cone bodies 5, 6 each have an offset to the other arranged central axis 10, 11. As a result, they are radially offset from one another, on each other and form a tangential on both sides of the double-cone burner 4 Air inlet slot 12, 13 through which combustion air 14 into the interior 9 flows (Fig. 2). Both partial cone bodies 5, 6 each have a cylindrical one Initial part 15, 16. The initial parts 15, 16 are analogous to the partial cone bodies 5, 6 staggered. In the beginning parts 15, 16 and in the interior 9 protruding is an end piece designed as a central liquid fuel nozzle 17 one serving the fuel supply of the double cone burner 4 Fuel lance 18 arranged (Fig. 1). The liquid fuel nozzle 17 has one simple, circular injection opening 19 (Fig. 2). This injection opening 19 has a diameter d and a guide length l, the quotient of the Guide length l and the diameter d is 4 (Fig. 3).

Of course, the injection opening 19 can correspond to the specific operating conditions the double cone burner 4 also another suitable shape and the quotient of the guide length and diameter an amount up to 6 to have. Of course, the double-cone burner 4 can be purely conical, i.e. without the cylindrical starting parts 15, 16 are formed (not shown).

Both partial cone bodies each have a fuel line provided with openings 20 21, 22, which at the end of the tangential air inlet slots 12, 13 is appropriate. Through the fuel lines 21, 22, the gaseous fuel 3 supplied and through the openings 20 into the tangential air inlet slots 12, 13 initiated. Mixing of the gaseous fuel 3 takes place there with the combustion air 14 flowing in from the outside. Combustion chamber side 1 the double cone burner 4 has a collar-shaped, as anchoring for the Partial cone body 5, 6 serving end plate 23 with a number of holes 24 (Fig. 1). If necessary, the combustion chamber 1 can pass through these bores 24 Cooling air 25 are supplied.

The double-cone burner 4 is also used as liquid fuel via the fuel lance 18 2 fuel oil used. The fuel oil 2 is through the central Injection opening 19 of the liquid fuel nozzle 17 with an injection angle α injected less than 10 ° into the interior 9. Because of this narrow injection angle initially arises in the interior 9 of the double-cone burner 4 very much compact full jet 26, which only opens downstream and in which the fuel droplets are evenly distributed over the entire cross-section. In contrast to the hollow cone-shaped one used in the prior art for double-cone burners However, such a full jet 26 has sufficient fuel spray in its center axial impulses so that the fuel droplets do not hit the inner walls 7, 8 of the partial cone body 5, 6 are worn. It can also have this effect due to a relatively high injection speed of the fuel oil 2 of 20 to 60 m / s to be reinforced.

The full jet 26 spreads in the interior 9 of the double-cone burner 4 in the direction of flow evenly and ultimately takes on a conical shape Shape. The full jet 26 of the through the tangential air inlet slots 12, 13 flowing, rotating combustion air 14 enclosed. The The resulting fuel mixture is ignited in the area of the burner orifice, whereby a flame front 27 is formed, which in turn is in the area the burner mouth is stabilized by a backflow zone 28.

Because the atomization of the fuel oil 2 mainly from the combustion air 14 is realized is not the injection speed of the full jet 26 but that Combustion air 14 crucial for the atomization quality and thus for the subsequent combustion. This will give you the flexibility you need reached to the double cone burner 4 or the combustion chamber 1 under all load conditions, i.e. from ignition to full load with the same injection concept to operate.

In addition, it is of course possible to use a fuel lance 18, not shown connected fuel pump also the pulse of the full jet 26 can be regulated so that depending on the premix burner 4 used and the current one Load state of the combustion chamber 1 required penetration depth of the fuel drops is achieved.

In a second embodiment, with an analog double-cone burner 4, the fuel lance 18 consists of a central liquid fuel tube 29, which is coaxially surrounded by an air tube 30 (Fig. 4). At the Operation of the double-cone burner 4 is therefore simultaneous with the injection of the Fuel oil 2, but radially outside and concentric with fuel oil 2 Shield air flow 31 introduced into the interior 9 of the double-cone burner 4. This screen air flow 31 is injected at a speed of approx. 30 m / s and a mass of 0.1 to 2.0% of the total air mass flow of the double-cone burner 4. In this way, an even more compact full jet 26 'generated, which bursts only at the end of the burner (Fig. 5). Cools and at the same time protects the air tube 30 into the interior 9 of the double-cone burner 4 arriving screen air flow 31 the liquid fuel pipe 29. All other processes take place essentially analogously to the first exemplary embodiment.

Reference list

1

Combustion chamber

2nd

Liquid fuel, fuel oil

3rd

gaseous fuel

4th

Premix burner, double cone burner

5

Partial cone body

6

Partial cone body

7

Inner wall, from 5

8th

Inner wall, from 6

9

inner space

10th

Central axis

11

Central axis

12th

Air inlet slot

13

Air inlet slot

14

Combustion air, combustion air flow

15

Initial part, cylindrical

16

Initial part, cylindrical

17th

Liquid fuel nozzle

18th

Fuel lance

19th

Injection port

20th

opening

21

Fuel line

22

Fuel line

23

End plate

24th

drilling

25th

Cooling air

26

Full jet

27

Flame front

28

Backflow zone

29

Liquid fuel pipe

30th

Air tube

31

Screen airflow

26 '

Full jet

α

Injection angle

d

diameter

l

Guide length

Claims (10)

Process for operating a premix burner with a central one Interior (9) of the premix burner (4) opening liquid fuel nozzle (17), characterized in that at least one liquid fuel (2) in a full jet (26, 26 '), with an injection angle α of less than 10 ° is injected into the interior (9) of the premix burner (4). A method according to claim 1, characterized in that radially outside and concentric with the at least one liquid fuel (2) Shield air flow (31) is introduced into the interior (9). A method according to claim 2, characterized in that the screen air flow (31) with a small mass is introduced into the interior (9). A method according to claim 3, characterized in that the screen air flow (31) approx. 0.1 to 2.0% of the total air mass flow of the premix burner (4) is. A method according to claim 4, characterized in that the screen air flow (31) at a speed of 5 to 60 m / s into the interior (9) is introduced. Method according to one of claims 1 to 5, characterized in that that in the interior (9) of the premix burner (4) in the direction of flow full jet (26, 26 ') spreading from a tangential into the premix burner (4) incoming, rotating combustion air flow (14) is enclosed, the ignition of the mixture in the area of the burner mouth takes place and the flame front (27) through in this area a backflow zone (28) is stabilized. Premix burner for performing the method according to one of the claims 1 to 6, characterized in that the liquid fuel nozzle (17) a simple one with a guide length (l) and a diameter (D) has formed injection opening (19). Premix burner according to claim 7, characterized in that the injection opening (19) a ratio of guide length (l) to diameter (d) of 4 ≤ l / d ≤ 6. Premix burner according to claim 8, characterized in that the premix burner (4) from at least two hollow, radially offset from each other arranged partial cone bodies (5, 6), with one in the flow direction enlarging, hollow-conical interior (9), tangential air inlet slots (12, 13) and the liquid fuel nozzle (17) with a the fuel supply serving fuel lance (18) is connected. Premix burner according to claim 9, characterized in that the Fuel lance (18) consists of a central liquid fuel tube (29), which is coaxially surrounded by an air tube (30).

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