EP1319895A2 - Lean-burn premix burner for gas turbine and its method of operation - Google Patents

Abstract

The fuel supply ring (4) includes multiple primary fuel nozzles and additional secondary fuel nozzles. The primary fuel nozzles are evenly distributed along a circumference of the fuel supply ring while the additional nozzles are distributed unevenly along fuel supply ring circumference. <??>An Independent claim is also included for an operation method for lean premix burner of gas turbine.

Description

The invention relates to a lean premix burner for a gas turbine with the features of the generic term of Main claim and a method for operating a lean premix burner.

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

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

Lean premix burners are from the prior art in a wide variety Design forms known.

Lean premix burners were developed, among other things, for the Avoid formation of nitrogen oxides. For this, the air-fuel ratio procedurally high, so that a very lean mixture is created. This creates in the main combustion zone relatively low combustion temperatures.

A disadvantage can be that by the relative low combustion temperatures the combustion itself is not as complete as it is at higher temperatures would. Thus unburned hydrocarbon and Carbon monoxide emissions.

Another disadvantage is that the very lean mixture leads to combustion control which, under normal circumstances, cannot be leaned much further without producing instabilities. A further thinning leads to the extinguishing of the flame. This means that additional so-called pilot burners must be available for safe, airworthy operation. These pilot burners ensure a high local combustion temperature. This in turn leads to high flame stability. A disadvantage of the operation of the pilot burner is that relatively high NO _x emissions arise.

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

The object of the invention is a lean premix burner and a method for operating a lean premix burner to create which under simple construction Avoiding the state of the art at low thermal Lead stress and even in very lean conditions burn safely.

According to the invention, the task with regard to the lean premix burner through the combination of features of the main claim solved, with regard to the method, the solution is done the task through the combination of features of the subordinate Claim. Show the respective subclaims further advantageous embodiments of the invention.

With regard to the lean premix burner, that additional to the primary fuel injector ring Fuel secondary nozzles are provided.

The lean premix burner according to the invention stands out through a number of significant advantages.

The additional fuel secondary nozzles make it possible to enrich the fuel-air mixture locally. It is therefore not necessary, additional pilot burners or the like provided. Rather, areas arise according to the invention on the fuel injector ring, where a richer There is a fuel-air mixture. This leads to one Combustion at higher temperatures and thus a more stable one Flame guide. This results in a more stable one Operation of the lean premix burner, the risk of extinguishing is avoided in a reliable manner. Especially Favorable embodiment of the invention is provided that the fuel primary nozzles evenly around the circumference of the fuel supply ring are distributed while the Fuel secondary nozzles distributed unevenly around the circumference are. It is particularly advantageous if the fuel secondary nozzles only in some sectors of the fuel injector ring are arranged. This ensures that individual areas of the fuel injector ring with a richer one Mixture can be supplied.

According to the invention, this results in an internal grading of Fuel supply via the fuel supply ring. The According to the invention, the fuel supply is switched in such a way that that selectively with low or low load near at least two fuel primary nozzles additional, adjacent Secondary fuel nozzles for enriching the fuel-air mixture be put into operation.

To the total amount of fuel in the respective load range of the gas turbine keeping constant are inventively other, unneeded primary fuel nozzles switched off.

If from the low or low load operation again full load operation is achieved a continuous increase in the fuel mass flow the fuel primary nozzles are switched on again. The then secondary fuel nozzles that are no longer required blown out accordingly.

To ensure safe operation even in a low load range To ensure it can be convenient if on the Fuel injector ring designed additional fuel mini-nozzles are. These mini fuel nozzles can be in groups be arranged (cluster).

With regard to the method according to the invention, it is therefore provided that that locally on the fuel supply ring richer air-fuel mixture is set while at other points on the fuel supply ring none Fuel is injected. As mentioned, that remains Total amount of fuel supplied to the lean premix burner becomes, essentially the same.

According to the invention, this results in a high level of flame safety (Stability) of the lean premix burner, so that additional Pilot burners can be dispensed with entirely. This makes the combustion chamber volume smaller. The surface too the combustion chamber decreases, which in turn the cooling air requirement drops. This results in an increase the efficiency of the gas turbine.

Another significant advantage of the invention is in that a continuous transition from full load operation to a low or low load operation can. On the discontinuous known from the prior art Fuel shift between pilot burners and Lean premix burners and the systems required for this can be dispensed with entirely according to the invention. From this again there is a better thrust course 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 BrennstoffPrimärdüsen,

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.

The invention is described below on the basis of exemplary embodiments in conjunction with the drawing. It shows:

Fig. 1

a simplified representation of a lean premix burner in a gas turbine combustion chamber,

Fig. 2

2 shows a schematic view along line AB of FIG. 1, which shows the arrangement of primary nozzles on the circumference,

Fig. 3

2 shows an enlarged partial sectional view of a fuel injector ring according to the invention,

Fig. 4

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

Fig. 5

4, a part-load or low-load operation,

Fig. 6

4 shows a representation, similar to FIGS. 4 and 5, showing differently switched lean premix burners,

Fig. 7

6 shows a modified illustration of FIG. 6,

Fig. 8

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

Fig. 9

an operating diagram of different load levels.

In the exemplary embodiments, the same parts are included provided with the same reference numbers.

Fig. 1 shows a schematic side view of an inventive Lean premixing module in a gas turbine combustion chamber. Reference number 1 denotes a flame tube, which is preceded by a lean premix burner. This comprises an outer housing 2 and an inner housing 3. There is a fuel injector ring on the inner housing 4 trained. Reference number 5 describes an inner body of the lean premix burner, with the reference number 6 fuel nozzles are shown in general.

Lean premix burners of this type are in their basic construction known from the prior art, so that further Executions can be dispensed with at this point.

Fig. 2 shows a sectional view along the line A-B of Fig. 1. Here are schematically on the fuel supply ring 4 several fuel nozzles 6 are shown. On the fuel supply itself and similar details have been waived here. Fig. 2 explains that some of the Fuel nozzles 6, namely the fuel nozzles 6a in operation are out of operation while the illustrated fuel nozzles 6b are.

In Fig. 3 is a section through an embodiment is enlarged again of the fuel supply ring according to the invention 4 shown. This includes two fuel supply channels 7, each of which has several fuel primary nozzles on the circumference 8 and fuel secondary nozzles 9 assigned are. 3 shows that that the fuel primary nozzles 8 and the fuel primary nozzles 9 each with their own fuel supply channels 7 are provided so that a different Fuel supply can take place.

4 and 5 each show an end view (greatly simplified) the arrangement of the fuel nozzles on the circumference of the fuel supply ring 4. At the illustration 4 are the individual fuel primary nozzles 8 evenly distributed around the circumference and are located accordingly in operation. In contrast, FIG. 5 shows overall four fuel nozzle sectors, in which different, Unevenly distributed orders of Fuel secondary nozzles 9 are shown. Since the Primary fuel nozzles 8 and primary fuel nozzles 9 in are different levels (see Fig. 3) 5 shows the arrangement of the fuel secondary nozzles 9th

6 and 7 show a simplified, schematic representation the arrangement of circumferentially graded lean premix burners. 6 shows a symmetrical peripheral circuit, at which lean premixing modules 14 are in operation are, with lean premixing modules 15, which are out of operation are, take turns. In contrast, an illustration is shown in FIG. 7 chosen with an asymmetrical circumferential gradation (grouping circumferential circuit) is selected. They are each several lean premixing modules 14 in operation side by side, while adjacent several lean premixing modules 15 out of operation are taken.

FIG. 8 shows a sectional view, similar to FIG. 2, in which additionally grouped fuel mini-nozzles 13 Arrangement (cluster) on the fuel supply ring 4 are provided. 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, primary fuel nozzles 8 are shown schematically.

9 shows a diagram in which the Mass fuel flow against the thermal load of the engine / the gas turbine is shown. The resulting Straight leads from the zero point through a full load point. To one Operation of the lean premix burner or lean premix module to ensure flame-proof in an annular combustion chamber, the burners are shown on the below three different operating levels.

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

A switching point is provided at the operating point I. There there is a gradation of entire burner modules in known symmetrical or asymmetrical way. The burner modules or lean premix burners are switched off in such a way that the lean premix burners that remain in operation or modules a thermal load of approximately 100% reach at switching point I. The switching takes place via valves, using switches or controllable valves can.

At a medium switching point II, which is about the Half of the thermal load of the first point I lie groups of injectors can be used up to now remaining lean premix burner or lean modules switched off. In this way, continued operation of the existing fuel injectors at 100% (at the switching point) of the individual fuel mass throughput. Especially can be advantageous in this low load range asymmetrical arrangement of the remaining fuel nozzles be provided (asymmetrical group connection).

At the third switching point III there is a further load reduction switching from the normal nozzles (fuel primary nozzles and fuel secondary nozzles) on clusters of Mini nozzles or secondary nozzle ring. Have these mini nozzles as described, a significantly smaller diameter than the normal nozzles. Guide the mini nozzles / secondary nozzles An acceptable fuel atomization behavior even at low loads with comparatively better droplet evaporation behavior and still generate a relative locally rich air-fuel mixture. The improved fuel atomization and the better drop evaporation behavior are also advantageous and important because in the low load range the gas turbine the delivery temperature of the compressor is low. According to the invention, it is therefore flame-retardant Mixture generated.

It can thus be stated that according to the invention a grouping or interconnection of individual modules of lean premix burners takes place in an annular combustion chamber, around the lean premix burners in operation Combine low load in groups. By switching off other lean premix burners or modules result from the remaining modules or lean premix burners at the same amount of fuel remaining in the combustion chamber fatter mixture. If the It is then a burden, or in connection with the one just described Measure, possible, additional secondary nozzles or mini nozzles to start up within a lean premix burner select individual areas in which (via seen the extent) in individual sectors a richer or richer fuel-air mixture is present. This will the flame safety etc. of the individual as described above Module or lean premix burner ensured.

The invention is not based on the exemplary embodiments shown limited, rather arise within the scope of the invention diverse options for modification and modification.

LIST OF REFERENCE NUMBERS

1

flame tube

2

Lean premix burner outer housing

3

inner housing of the lean premix burner

4

Lean premix burner fuel supply ring

5

Lean premix burner inner body

6

general fuel nozzles

7

general fuel supply channel

8th

Fuel primary nozzle

9

Fuel secondary nozzle

12

Fuel nozzle sector

13

Fuel Minidüse

14

Lean premixing module in operation

15

Lean premixing module out of operation

Claims (11)

Lean premix burner for a gas turbine, with at least one fuel injector ring (4) provided with fuel primary nozzles (8),
characterized in that
additional fuel secondary nozzles (9) are provided on the fuel supply ring (4). Lean premix burner according to claim 1,
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 distributed unevenly on the circumference. Lean premix burner according to claim 2,
characterized in that
the fuel secondary nozzles (9) are arranged only in some sectors of the fuel supply ring (4). Lean premix burner according to claim 1,
characterized in that
on the fuel supply ring (4) fuel mini-nozzles (13) are formed. Lean premix burner according to claim 4,
characterized in that
the fuel mini-nozzles (13) are arranged in groups. Lean premix burner according to one of claims 1 to 5,
characterized in that
the fuel secondary nozzles (9) and / or the fuel mini-nozzles (13) deliver a richer air-fuel mixture. Method for operating a lean premix burner for a gas turbine with at least one fuel supply ring (4) provided with fuel primary nozzles (8), on which additional fuel secondary nozzles (9) are provided,
characterized in that
at low or low load of the gas turbine, a richer air-fuel mixture is set locally on the fuel supply ring (4), while at other points in the fuel supply ring (4) no fuel is injected via the primary nozzles (8), the Total amount of fuel that is fed to the lean premix burner remains essentially the same. Method according to claim 7,
characterized in that
at low or low load of the gas turbine adjacent to at least two fuel primary nozzles (8) fuel secondary nozzles (9) for local enrichment of the fuel-air mixture. Method according to one of claims 7 or 8,
characterized in that
the primary fuel nozzles (8), which are not arranged adjacent to the secondary fuel nozzles (9), are switched off. Method according to one of claims 7 to 9,
characterized in that
if the load on the gas turbine is reduced further, the local supply of a richer fuel-air mixture is provided by additional fuel mini-nozzles (13). A method according to claim 10,
characterized in that
the fuel primary nozzles (8), fuel secondary nozzles (9) and fuel mini nozzles (13), which are in operation, are switched in local groups on the circumference of the fuel supply ring (4).

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