EP1319895B1 - Lean-burn premix burner for gas turbine and its method of operation - Google Patents

Description

The invention relates to a lean burn burner for a gas turbine with the features of the preamble of the main claim and to a method for operating a lean burn burner.

In particular, the invention relates to a lean burn burner with at least one fuel feed ring provided with primary fuel nozzles.

Such a lean burn burner can be designed either as an LPP module or as a swirl cup.

Magervormischbrenner are known from the prior art in a variety of Ausgestaltunsformen.

For example, lean burn burners have been developed to prevent the formation of nitrogen oxides. For this purpose, the air-fuel ratio is set high due to the process, resulting in a very lean mixture. This produces relatively low combustion temperatures in the main burnup zone.

It may be disadvantageous that due to the relatively low combustion temperatures, the combustion itself is not as complete as it would be at higher temperatures. This produces unburned hydrocarbon and carbon monoxide emissions.

A further disadvantage is that a combustion guide is achieved by the very lean mixture, which under normal circumstances can not be carried much further without creating instabilities. Another transformation finally leads to the extinction of the flame. It follows that additional so-called pilot burners must be available for safe, aviation-efficient operation. These pilot burners ensure a high local combustion temperature. This in turn leads to a high flame stability. A disadvantage of the operation of the pilot burner, it turns out that relatively high NO _x emissions arise.

The prior art shows the use of these pilot burners in axially stepped combustors used with lean burn burners. Such combustion chambers are relatively large, they have a complex geometry and have a large surface to be cooled.

The US Pat. No. 6,109,038 A discloses a burner having two concentric independent fuel supply rings. These are each provided with fuel outlet openings, which serve to introduce fuel into different air flow paths

The US 5,351,477 A. discloses a separate fuel conduit disposed in a gas-fuel conduit and serving to deliver additional fuel. It is thus provided fuel supply ring, which is equipped with additional fuel nozzles.

The US 4 222 243 A shows fuel ports, which are arranged on two axially staggered rings and can be controlled separately.

The invention is based on the object to provide a lean burn burner and a method for operating a lean burn burner, which lead in a simple structure while avoiding the prior art to a low thermal load and burn safely even under very lean conditions.

According to the invention, the object is achieved with regard to the lean burn burner by the combination of features of the main claim, with regard to the method, the solution of the problem by the feature combination of the independent claim. The respective subclaims show further advantageous embodiments of the invention.

The lean burn burner according to the invention is characterized by a number of significant advantages.

The additional fuel secondary nozzles, it is possible to locally enrich the fuel-air mixture. It is thus not necessary to provide additional pilot burners or the like. Rather, according to the invention, there are areas on the fuel injection ring at which a richer fuel-air mixture is present. This leads to combustion at higher temperatures and thus to a more stable flame guidance. This results in a more stable operation of the lean burn burner, the risk of extinction is thereby avoided in a reliable manner. In the invention it is provided that the fuel primary nozzles are evenly distributed on the circumference of the fuel supply ring, while the fuel secondary nozzles are distributed unevenly around the circumference. It is particularly advantageous if the fuel secondary nozzles are arranged only in some sectors of the fuel injection system. This ensures that individual areas of the fuel injection system can be supplied with a richer mixture.

According to the invention thus results in an internal gradation of the fuel supply via the fuel supply ring. The fuel supply is switched according to the invention so that selectively at low or low load in the vicinity of at least two primary fuel nozzles additional, adjacent fuel secondary nozzles for enrichment of the fuel-air mixture are put into operation.

In order to keep constant in the respective load range of the gas turbine, the total amount of fuel, according to the invention other, unnecessary fuel primary nozzles are turned off.

If a change is made from the low-load or low-load mode to a full-load mode, the primary fuel nozzles are switched on again in order to achieve a continuous increase in the fuel mass flow. The then no longer required fuel secondary nozzles are blown out accordingly.

In order to ensure safe operation even in a low load range, it may be favorable if additional fuel mini nozzles are formed on the fuel injection ring. These fuel mini nozzles can be arranged in groups (clusters).

With regard to the method according to the invention, it is thus provided that a richer air-fuel mixture is locally adjusted at the fuel supply ring, while no fuel is injected at other locations of the fuel supply ring. As mentioned, the total amount of fuel supplied to the lean premix burner remains substantially the same.

According to the invention thus results in a high flame resistance (stability) of the lean burn burner, so that can be completely dispensed with additional pilot burner. As a result, the combustion chamber volume is smaller. The surface of the combustion chamber is also reduced, which in turn reduces the cooling air requirement. This results in an increase in the efficiency of the gas turbine.

Another significant advantage of the invention is that a continuous transition from full load to low or low load can be made. On the known from the prior art discontinuous fuel shift between pilot burners and Magervormischbrennern and the systems required for this purpose can be completely dispensed with according to the invention. This in turn results in a better thrust curve when switching the gas turbine to different load ranges.

Fig. 1

eine vereinfachte Darstellung eines Magervormischbrenners in einer Gasturbinenbrennkammer,

Fig. 2

eine Prinzipansicht entlang der Linie A-B von Fig. 1, die die Anordnung von Primärdüsen am Umfang zeigt,

Fig. 3

eine vergrößerte Teil-Schnittansicht eines erfindungsgemäßen Brennstoff-Eindüserings,

Fig. 4

eine stark vereinfachte schematische stirnseitige Ansicht eines Brennstoff-Versorgungsrings mit gleichmäßiger Verteilung der Brennstoff-Primärdüsen,

Fig. 5

eine Ansicht analog Fig. 4, eines Teillast- oder Niedriglastbetriebs,

Fig. 6

eine Darstellung, ähnlich den Fig. 4 und 5, mit Darstellung unterschiedlich geschalteten Magervormischbrennern,

Fig. 7

eine abgewandelte Darstellung der Fig. 6,

Fig. 8

eine Schnittansicht, ähnlich Fig. 2, zur Darstellung von Brennstoff-Minidüsen, und

Fig. 9

ein Betriebsdiagramm unterschiedlicher Laststufen.

In the following the invention will be described by means of embodiments in conjunction with the drawing. Showing:

Fig. 1

a simplified representation of a lean burn burner in a gas turbine combustor,

Fig. 2

1 is a schematic view along the line AB of FIG. 1, showing the arrangement of primary nozzles on the circumference;

Fig. 3

an enlarged partial sectional view of a fuel Eindüsserings invention,

Fig. 4

a greatly simplified schematic frontal view of a fuel supply ring with uniform distribution of the fuel primary nozzles,

Fig. 5

a view analogous to FIG. 4, a partial load or low load operation,

Fig. 6

a representation, similar to FIGS. 4 and 5, showing differently connected lean burn burners,

Fig. 7

a modified representation of FIG. 6,

Fig. 8

a sectional view, similar to Figure 2, showing fuel mini-nozzles, and

Fig. 9

an operating diagram of different load levels.

In the embodiments, the same parts are each provided with the same reference numerals.

1 shows a schematic side view of an inventive lean premix module in a gas turbine combustor. The reference numeral 1 denotes a flame tube, which is preceded by a lean premix burner. This comprises an outer housing 2 and an inner housing 3. On the inner housing, a fuel-injection ring 4 is formed. The reference numeral 5 describes an inner body of the lean premix burner, with the reference numeral 6 are generally fuel nozzles shown.

Such lean burn burners are known in their basic construction from the prior art, so that it is possible to dispense with further embodiments at this point.

FIG. 2 shows a sectional view along the line A-B of FIG. 1. Here, a plurality of fuel nozzles 6 are shown schematically on the fuel supply ring 4. On the fuel supply itself and similar details was omitted here. FIG. 2 explains that individual ones of the fuel nozzles 6, namely the fuel nozzles 6a are in operation while the illustrated fuel nozzles 6b are out of operation.

In Fig. 3 is again enlarged a section through an embodiment of the fuel supply ring according to the invention 4. This comprises two fuel supply ducts 7, which each have a plurality of fuel primary nozzles 8 and fuel secondary nozzles 9 are assigned at the periphery. From the representation of FIG. 3 it follows that the fuel primary nozzles 8 and the fuel primary nozzles 9 are each provided with their own fuel supply channels 7, so that a different supply of fuel can take place.

FIGS. 4 and 5 each show in an end view (greatly simplified) the arrangement of the fuel nozzles on the circumference of the fuel supply ring 4. In the illustration of Fig. 4, the individual fuel primary nozzles 8 are evenly distributed around the circumference and are accordingly in Business. In contrast, Fig. 5 shows a total of four fuel nozzle sectors in which different, unevenly distributed over the circumference arrangements of fuel secondary nozzles 9 are shown. Since the fuel primary nozzles 8 and the fuel primary nozzles 9 are located in different planes (see FIG. 3), the arrangement of the fuel secondary nozzles 9 shown in FIG. 5 results.

Figures 6 and 7 show, in a simplified schematic representation, the arrangement of circumferentially graded lean burn burners. FIG. 6 shows a symmetrical peripheral circuit in which lean premix modules 14 which are in operation alternate with lean premix modules 15 which are out of operation. On the other hand, in Fig. 7, a diagram is selected in which an asymmetrical circumferential step (grouping peripheral circuit) is selected. Each of a plurality of lean premix modules 14 are operating side-by-side, while adjacent several bulk premix modules 15 are taken out of service.

FIG. 8 shows a sectional view, similar to FIG. 2, in which fuel mini-nozzles 13 are additionally provided in a clustered arrangement on the fuel supply ring 4. These fuel mini-nozzles 13 have a higher injection speed of the fuel and thereby lead to a locally richer fuel-air mixture. Adjacent to the fuel mini-nozzles 13 schematically fuel-primary nozzles 8 are shown.

In Fig. 9 is a diagram is shown, in which the fuel mass flow is shown against the thermal load of the engine / the gas turbine. The resulting straight line leads from the zero point through a full load point. In order to ensure flameproof operation of the lean burn burner or lean premixing modules in an annular combustion chamber, the burners are switched to the three different operating stages shown below.

The following description refers to a reduction in engine power, but analogous applies to a corresponding load increase.

At the operating point I, a switching point is provided. There is a circumferential gradation of whole burner modules in a known symmetrical or asymmetric manner. The burner modules or lean burn burners are switched off in such a way that the lean burn burners or modules remaining in operation reach a thermal load of approximately 100% at the switching point I. The circuit is via valves, with switches or controllable valves can be used.

At a middle switching point II, which may be about half the thermal load of the first point I, groups of injectors of the previously left in operation lean burn burner or lean modules are turned off. This achieves a continued operation of the existing fuel injectors at 100% (at the switching point) of the individual fuel mass flow rate. Particularly advantageously, in this low-load range, an asymmetrical arrangement of the fuel nozzles remaining in operation can be provided (asymmetric group circuit).

At the third switching point III is a further load reduction switching from the normal nozzles (fuel primary nozzles and fuel secondary nozzles) on clusters of mini nozzles or secondary Eindüssering before. These mini nozzles have, as described, a significantly smaller diameter than the normal nozzles. The mini nozzles / secondary nozzles lead to an acceptable fuel Zersteubungsverhalten at low load with comparatively better droplet evaporation behavior and yet locally produce a relatively rich air-fuel mixture. The improved fuel atomization and better droplet evaporation behavior are also advantageous and important because in the low load range of the gas turbine, the delivery temperature of the compressor is low. According to the invention, a flameproof mixture is thus produced.

It is thus to be noted that, according to the invention, a grouping or interconnection of individual modules of lean premix burners takes place in an annular combustion chamber in order to combine the lean burn burners in operation into groups at low load. By switching off other lean burn burner or modules results in the remaining modules or lean burn burner with a constant fuel quantity of the combustion chamber a richer or richer mixture. With a further reduction of the load, it is then possible, or in conjunction with the measure just described, to set in operation additional secondary nozzles or mini-nozzles in order to select individual areas within a lean burn burner in which (seen in the circumferential direction) a single sector richer or richer fuel-air mixture is present. As a result, the flame safety, etc., as described above, of the single module or lean burn burner is ensured.

The invention is not limited to the embodiments shown, but rather arise within the scope of the invention varied modification and modification options.

LIST OF REFERENCE NUMBERS

1

flame tube

2

outer casing of the lean premix burner

3

inner casing of the lean premix burner

4

Fuel supply ring of the lean premix burner

5

inner body of the lean premix burner

6

general fuel nozzles

7

general fuel supply duct

8th

Fuel primary nozzle

9

Fuel secondary nozzle

12

Fuel nozzle sector

13

Fuel Minidüse

14

Magervormischmodul in operation

15

Magervormischmodul out of service

Claims (10)

1. Lean-burn premix burner for a gas turbine with at least one fuel supply ring (4) provided with primary fuel nozzles (8), at which additional secondary fuel nozzles (9) are arranged, with the fuel supply to the secondary fuel nozzles (9) being independent of the fuel supply to the primary fuel nozzles (8), characterized in that the primary fuel nozzles (8) are evenly distributed on the circumference of the fuel supply ring (4), while the secondary fuel nozzles (9) are unevenly distributed on the circumference.
2. Lean-burn premix burner in accordance with Claim 1, characterized in that the secondary fuel nozzles (9) are arranged only in some sectors of the fuel supply ring (4).
3. Lean-burn premix burner in accordance with Claim 1, characterized in that fuel mini-nozzles (13) are provided on the fuel supply ring (4).
4. Lean-burn premix burner in accordance with Claim 3, characterized in that fuel mini-nozzles (13) are arranged in groups.
5. Lean-burn premix burner in accordance with one of the Claims 1 to 4, characterized in that the secondary fuel nozzles (9) and/or the fuel mini-nozzles (13) supply a richer air-fuel mixture.
6. Method for the operation of a lean-burn premix burner for a gas turbine with at least one fuel supply ring (4) provided with primary fuel nozzles (8), at which additional secondary fuel nozzles (9) are arranged, characterized in that at low or reduced load conditions of the gas turbine a richer air-fuel mixture is set locally on the fuel supply ring (4) via the secondary fuel nozzles (9), while at other locations of the fuel supply ring (4) no fuel is injected via the primary fuel nozzles (8), with the total fuel quantity supplied to the lean-burn premix burner essentially remaining constant.
7. Method in accordance with Claim 6, characterized in that at low or reduced load conditions of the gas turbine secondary fuel nozzles (9) are activated in the vicinity of at least two primary fuel nozzles (8), to locally enrich the fuel-air mixture.
8. Method in accordance with Claim 6 or 7, characterized in that the primary fuel nozzles (8) not arranged in the vicinity of the secondary fuel nozzles (9) are shut-off.
9. Method in accordance with one of the Claims 6 to 8, characterized in that with further decreasing load of the gas turbine, local supply of richer fuel-air mixture is accomplished via additional fuel mini-nozzles (13).
10. Method in accordance with Claim 9, characterized in that the respective primary fuel nozzles (8), secondary fuel nozzles (9) and fuel mini-nozzles (13), which are in operation, are combined to form local groups on the circumference of the fuel supply ring (4).

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