EP2037172A2 - Gas turbine manager furnace with fuel nozzle with controlled fuel homogeneity - Google Patents

Abstract

Main-fuel injection (18) has central recesses (23) for controlled inhomogeneous fuel injection, especially in a peripheral direction. Their number on the periphery amounts to between 8 and 40 and, in a peripheral direction, they have a delta 2 setting angle of 10[deg] = delta 2 = 60[deg] and a delta 1 axial setting angle opposite a burner's axis between -10[deg] = delta 1 = 90[deg] . The central recesses are arranged in a single row, in multiple rows or in a zigzag layout.

Description

The invention relates to a gas turbine lean burn burner according to the features of the preamble of claim 1.

In particular, the invention relates to a fuel nozzle with controlled fuel inhomogeneity, which provides the opportunity to introduce the fuel in an optimal manner for combustion.

To reduce the thermally induced nitrogen oxide emissions different concepts for fuel nozzles are known. One possibility is the operation of burners with a high air-fuel excess. Here, the principle is exploited that due to a lean mixture and at the same time ensuring sufficient spatial homogeneity of the fuel-air mixture, a reduction in the combustion temperatures and thus the thermally induced nitrogen oxides is possible. In many such burners also a so-called internal fuel staging is applied. This means that in addition to a main fuel injection designed for low NOx emissions, a so-called pilot stage is also integrated into the burner, which is operated with an increased proportion of fuel and air and should ensure the stability of the combustion, adequate combustion of the combustion chamber and sufficient ignition properties (see Fig. 1 ). The main stage of the known so-called lean burners is often designed as a so-called film depositor ( US 2006/0248898 A1 ). In addition to the film-forming variants, some injection methods with single-jet injection are known which are intended to ensure a high degree of homogenization of the initial fuel distribution and / or a high penetration depth of the injected fuel ( US 2004/0040311 A1 ).

Another feature of known burners is the presence of so-called stabilizer elements which stabilize of flames used in combustion chambers (see Fig. 2 ). Most common application are in addition to streamline bodies especially so-called bluff body geometries, which may be designed as baffle plates or V-shaped stabilizers arranged (eg US 4445339 and WO 10/860659 ). By placing a bluff body in the flow, the flow velocity in the wake of the stabilizer is reduced. The flow experiences a strong acceleration at the edge of the bluff body, so that due to the high pressure gradient downstream of the bluff body separation of the boundary layer occurs, associated with the formation of a recirculating vortex system in the wake of the bluff body. If there is a combustible mixture at the edge of the recirculation zone or hot combustion products are already present in the vicinity of the bluff body, the probability of the flame velocity approaching the flow velocity increases as a result of the penetration of an ignitable mixture or the hot combustion products into the recirculation zone.

For the known burner concepts, the local fuel-air mixture is not controlled adjustable. In particular, in the previously discussed filming concepts, the problem is that with a desired homogeneous axial and circumferential loading of the fuel on the film layer Although a very good air-fuel mixture with average low combustion temperatures and thus low NOx emissions can be achieved, however the homogeneous mixture formation aimed at under high load conditions under partial load conditions as a result of insufficient fuel loading on the film former lead to a significant deterioration of the combustion chamber burnout (cf. Fig. 6 ). The background is the reduced heat release associated with lean mixtures as well as the property for local flame extinction with successive reduction of the fuel and low combustion chamber pressure and temperature.

There are also disadvantages with regard to flame anchoring by means of the known stabilizers. In general, adjustment of the size of the recirculation in the wake of the stabilizer can be achieved via the dimension of the flame holder, such as the outer diameter and the drag coefficient of the flow blockage. An application for a flame holder for a low-emission lean burn burner is, for example, from ( US Pat. No. 6,272,840 B1 ) known. Disadvantage of such an application, however, is that with the help of the selected geometry of the flame stabilizer only a certain flow shape adjustable and the shear layer between the accelerated and the delayed flow is characterized by very high turbulence. For such a flame stabilizer with V-shaped geometry is known that by forming a strong flow acceleration ("jet") in the wake of a centrally located on the burner axis pilot burner, a high lean Verlöschstabilität the flame can be achieved. This is achieved by a continuous reduction in the flow rate of the pilot jet further downstream, the formation of a recirculation in the wake of the flame stabilizer and the return of hot combustion gases upstream in the vicinity of the stabilizer (see Fig. 3 ). However, with this flame stabilization often increased soot and nitrogen oxide (NOx) emissions can occur. This flow shape can be achieved for example by a small outlet diameter A = A1 for the inner leg of the flame stabilizer.

As state of the art is still on the US 2002/0011064 A1 to refer.

Another flow form is characterized by a so-called "unfolding" of the flow and the formation of a recirculation area on the burner axis (see Fig. 4 ). This effect of "unfolding" the flow and forming a large return flow zone on the burner axis can be achieved by enlargement of the outlet diameter A = A2 can be achieved. In addition to the central recirculation, an attenuated recirculation area in the wake of the stabilizer is additionally present in this variant of the flame stabilizer. As a consequence of this arrangement, lower soot and NOx emissions are favored, while at the same time reducing flame stability from lean extinction.

It can be seen from the effects described that with the previously known flame stabilizer geometries only a specific flow shape can be set, which, however, can only be adjusted to improve some operating parameters, e.g. contributes to the poor extinguishing stability while at the same time reducing the deterioration of other operating parameters, e.g. soot and NOx emissions.

The invention has for its object to provide a Gasturbinenmagerbrenner of the type mentioned, which has a low structure while avoiding the disadvantages of the prior art low pollutant emissions, improved flame stability and a high Brennkammerausbrand.

According to the invention the object is achieved by combination of features of claim 1. The subclaims show further advantageous embodiments of the solution according to the invention.

Fig. 1:

Stand der Technik, Brenner für eine Fluggasturbine ( US 6 543 235 B1 );

Fig. 2:

Stand der Technik, Beispiel eines konventionell ausgebildeten Flammenstabilisators mit V-Form Geo- metrie ( US 6 272 840 B1 );

Fig. 3:

Stand der Technik, Berechnete Strömungsform in Abhängigkeit vom Austrittsdurchmesser des inneren Schenkels des Flammenstabilisators, Beispiel für eine Brennkammerströmung mit ausgeprägter dezentra- ler Rezirkulation im Nachlauf des Flammenstabilisa- tors infolge eines kleinen Austrittsdurchmessers A = A1;

Fig. 4:

Stand der Technik, Berechnete Strömungsform in Abhängigkeit vom Austrittsdurchmesser des inneren Schenkels des Flammenstabilisators, Beispiel für eine Brennkammerströmung mit zentraler Rezirkulation und deutlich verkleinertem Rezirkulationsgebiet im Nachlauf des Flammenstabilisators infolge eines ver- größerten Austrittsdurchmessers A = A2;

Fig. 5:

Berechnete "gemischte" Strömungsform mit zentraler Rezirkulation sowie ausgeprägter dezentraler Rezir- kulation im Nachlauf eines konturierten Flammensta- bilisators infolge eines im Umfang veränderlichen Austrittsdurchmessers des Flammenstabilisators A1 < A ≤ A2;

Fig. 6:

Brennkammerausbrand vs. Brennstoffanteil des Pilot- brenners, Schematische Darstellung des Ausbrandver- haltens für einen Filmleger sowie für eine diskrete Kraftstoffstrahleindüsung für die Hauptstufe des Ma- gerbrenners bei Teillastbedingungen;

Fig. 7:

Hauptkomponenten für den erfindungsgemäßen Magerbrenner, Ausführungsvariante mit diskretem Kraftstoffeintrag des Hauptkraftstoffs über Einzel- bohrungen an der inneren Oberfläche der Hauptkraft- stoffeinspritzung sowie mit blütenförmiger Geometrie für den inneren Schenkel des Flammenstabilisators;

Fig. 8:

Hauptkomponenten für den erfindungsgemäßen Magerbrenner, Ausführungsvariante mit diskretem Kraftstoffeintrag des Hauptkraftstoffs über einen Filmspalt an der inneren Oberfläche der Hauptkraft- stoffeinspritzung sowie mit blütenförmiger Geometrie für den inneren Schenkel des Flammenstabilisators;

Fig. 9:

Berechnete Umfangsverteilung der Kraftstoff-Luft- Verteilung im Nachlauf der Hauptkraftstoffeinsprit- zung des Brenners: Ausführungsform mit gezielter In- homogenität des Kraftstoffeintrags durch angestellte diskrete Kraftstoffbohrungen (Beispiel, n = 24);

Fig. 10:

Hauptstufe des erfindungsgemäßen Brenners: Darstel- lung der berechneten Strahleindringung in den mitt- leren Strömungskanal;

Fig. 11:

Ausführungsvariante des erfindungsgemäßen Brenners mit Darstellung der Anstellung der Kraftstoffbohrun- gen in axialer Richtung δ1 sowie Anstellung der inne- ren stromabseitigen Oberfläche der Hauptkraftstoff- einspritzung β;

Fig. 12:

Ausführungsvariante des erfindungsgemäßen Brenners mit Darstellung der Anstellung der Kraftstoffbohrun- gen in Umfangsrichtung δ2;

Fig. 13:

Ausführungsvariante des erfindungsgemäßen Brenners mit filmartiger Platzierung des Hauptkraftstoffs mit lokalen Kraftstoffanreicherungen, schematische Dar- stellung der stromaufseitigen Zumessung des Haupt- kraftstoffs über Einzelbohrungen;

Fig. 14:

Ausführungsform für einen Flammenstabilisator mit Konturierung der Austrittsgeometrie des inneren Schenkels, blütenförmige Geometrie;

Fig. 15:

Weitere Ausführungsform für einen Flammenstabilisa- tor mit stärkerer Konturierung der Austrittsgeomet- rie des inneren Schenkels, blütenförmige Geometrie;

Fig. 16:

Weitere Ausführungsform für einen Flammenstabilisa- tor mit Konturierung der Austrittsgeometrie des in- neren Schenkels, blütenförmige Geometrie mit gegenü- berliegender asymmetrischer Variation des Austritts- durchmessers;

Fig. 17:

Weitere Ausführungsform für einen Flammenstabilisa- tor mit Konturierung der Austrittsgeometrie des in- neren Schenkels, exzentrische Austrittsgeometrie;

Fig. 18:

Ausführungsform für einen Flammenstabilisator mit variabler Austrittsgeometrie, Darstellung von Posi- tionierungsmöglichkeiten von variablen Geometrieelementen (z.B. Piezo- oder Bi-Metall-Ele- mente) in den unteren und oberen Schenkel des Flam- menstabilisators, und

Fig. 19:

eine Ausführungsvariante des erfindungsgemäßen Bren- ners mit filmartiger Platzierung des Hauptkraft- stoffs mit lokalen Kraftstoffanreicherungen durch Turbulatoren stromab des Filmspalts.

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

Fig. 1:

Prior art burner for an aircraft gas turbine ( US Pat. No. 6,543,235 B1 );

Fig. 2:

State of the art, example of a conventionally designed flame stabilizer with V-shape geometry ( US Pat. No. 6,272,840 B1 );

3:

PRIOR ART, Calculated flow shape as a function of the exit diameter of the inner leg of the flame stabilizer, example of a combustion chamber flow with pronounced decentralized recirculation in the wake of the flame stabilizer as a result of a small exit diameter A = A1;

4:

PRIOR ART, Calculated flow shape as a function of the exit diameter of the inner leg of the flame stabilizer, example of a combustion chamber flow with central recirculation and clearly reduced recirculation area in the wake of the flame stabilizer as a result of an increased exit diameter A = A2;

Fig. 5:

Calculated "mixed" flow regime with central recirculation and pronounced decentralized recirculation in the wake of a contoured flame stabilizer due to a variable diameter exit diameter of the flame stabilizer A1 < A ≤ A2;

Fig. 6:

Combustion burnout vs. Fuel fraction of the pilot burner, Schematic representation of the burn-out behavior for a film lay- er as well as a discrete fuel-jet injection for the main stage of the fuel burner under partial load conditions;

Fig. 7:

Main components for the lean burn burner according to the invention, embodiment variant with discrete fuel input of the main fuel via individual bores on the inner surface of the main fuel injection and with flower-shaped geometry for the inner leg of the flame stabilizer;

Fig. 8:

Main components for the lean burn burner according to the invention, embodiment variant with discrete fuel input of the main fuel over a film gap on the inner surface of the main fuel injection and with flower-shaped geometry for the inner leg of the flame stabilizer;

Fig. 9:

Calculated circumferential distribution of the fuel-air distribution in the wake of the main fuel injection of the burner: embodiment with targeted inhomogeneity of the fuel input by employed discrete fuel bores (example, n = 24);

Fig. 10:

Main stage of the burner according to the invention: depiction of the calculated jet penetration into the central flow channel;

Fig. 11:

Embodiment variant of the burner according to the invention with representation of the setting of the fuel bores in the axial direction δ1 and employment of the inner downstream surface of the main fuel injection β;

Fig. 12:

Embodiment variant of the burner according to the invention with representation of the employment of fuel bores in the circumferential direction δ2;

Fig. 13:

Embodiment variant of the burner according to the invention with film-like placement of the main fuel with local fuel enrichments, schematic representation of the upstream metering of the main fuel via individual bores;

Fig. 14:

Embodiment for a flame stabilizer with contouring of the exit geometry of the inner leg, flower-shaped geometry;

Fig. 15:

Further embodiment for a flame stabilizer with more pronounced contouring of the exit geometry of the inner leg, flower-shaped geometry;

Fig. 16:

Further embodiment for a flame stabilizer with contouring of the outlet geometry of the inner leg, flower-shaped geometry with opposite asymmetrical variation of the outlet diameter;

Fig. 17:

Further embodiment for a flame stabilizer with contouring of the exit geometry of the inner leg, eccentric exit geometry;

Fig. 18:

Embodiment for a flame stabilizer with variable exit geometry, representation of possible positioning of variable geometry elements (eg piezo or bimetallic elements) in the lower and upper limb of the flame stabilizer, and

Fig. 19:

an embodiment variant of the burner according to the invention with film-like placement of the main fuel with local fuel enrichments by turbulators downstream of the film gap.

According to the invention, a burner operated with excess air (see Fig. 7 ) having a pilot 17 and a main fuel injection 18. Within the main stage, the aim is to set a targeted inhomogeneity of the fuel-air mixture. The goal is to create a load-dependent variation of fuel placement in the main stage of the fuel in order to influence the degree of local fuel-air mixture. The background is that a high mixture homogenization on the one hand favors the formation of low NOx emissions, on the other hand, a reduced mixture homogenization by targeted formation of locally rich mixture zones advantageous for achieving a high burnout of the combustion chamber, especially at partial load conditions. The partially competing properties are to be optimized by the method of load-dependent fuel inhomogeneity. Furthermore, the burner is characterized by a novel flame stabilizer between the inner and middle flow channel, which should lead to improved flow control within the combustion chamber, in particular with regard to the interaction of the pilot and main flow in addition to the method for local load-dependent fuel enrichment.

• Als bevorzugte Methode zur Einstellung von lokalen Kraftstoffinhomogenitäten wird eine diskrete Strahleindüsung über mehrere Kraftstoffbohrungen n für die Hauptstufe eines Magerbrenners vorgeschlagen. Vorzugsweise sind zwischen n = 8 und n = 40 Bohrungen vorgesehen. Die Bohrungen können dabei gleichmäßig als auch ungleichmäßig im Umfang verteilt sein. Weiterhin ist eine einreihige als auch mehrreihige sowie gestaffelte Anordnung der Bohrungen möglich. Über geeignete konstruktive Maßnahmen kann eine kontrollierte Einstellung der Eindringtiefe der diskreten Kraftstoffstrahlen und damit der Güte der lokalen Kraftstoff-Luft-Mischung erreicht werden. Der größte Druckabfall in der Hauptkraftstoffleitung und damit der die Zumessung des Kraftstoffs bestimmende Querschnitt befindet sich an bzw. in der Nähe der inneren Oberfläche der Hauptstufe 19. Die diskrete Eindüsung des Kraftstoffs über Bohrungen erfolgt unter einem bestimmten Winkel zur Brennerachse radial nach innen in den mittleren Strömungskanal 15. Die Eindüsung des Kraftstoffs der Hauptstufe kann dabei sowohl an der stromauf- als auch stromabseitigen Oberfläche der Hauptkraftstoffeinspritzung erfolgen 38, 19. Die vorgeschlagene Methode der diskreten Strahleindüsung für die Hauptstufe eines Magerbrenners zeichnet sich durch eine lastabhängige Eindringtiefe der diskreten Strahlen aus. Bei niedrigen bis mittleren Betriebsbedingungen, bei der die Hauptstufe zur Gewährleistung verringerter NOx- und Ruß-Emissionen zusätzlich zur Pilotstufe zugeschaltet wird, ist infolge des verringerten Kraftstoffdrucks - und damit infolge eines niedrigen Kraftstoff-Luft-Impulsverhältnisses - die Eindringtiefe der diskreten Kraftstoffstrahlen gering. Bei höheren Lastbedingungen steigt das Kraftstoff-Luft-Impulsverhältnis deutlich an und führt zu einem tieferen Eindringen der Kraftstoffstrahlen in den mittleren Strömungskanal.

Controlled fuel inhomogeneity through a discrete jet injection:

• As a preferred method for adjusting local fuel inhomogeneities, a discrete jet injection over a plurality of fuel wells n for the main stage of a lean burn burner is proposed. Preferably, between n = 8 and n = 40 holes are provided. The holes can be distributed evenly as well as unevenly around the circumference. Furthermore, a single-row and multi-row and staggered arrangement of the holes is possible. By appropriate design measures, a controlled adjustment of the penetration depth of the discrete fuel jets and thus the quality of the local fuel-air mixture can be achieved. The largest pressure drop in the main fuel line and thus the metering of the fuel defining cross section is located at or in the vicinity of the inner surface of the main stage 19. The discrete injection of the fuel through holes is carried out at a certain angle to the burner axis radially in the middle flow channel 15. The injection of the fuel of the main stage can take place both at the upstream and downstream surface of the main fuel injection 38, 19. The proposed method of discrete jet injection for the main stage of a lean burn burner is characterized by a load-dependent penetration depth of discrete rays out. At low to medium operating conditions, where the main stage is switched on in addition to the pilot stage to ensure reduced NOx and soot emissions, the penetration depth of the discrete fuel jets is low due to the reduced fuel pressure, and hence low fuel to air pulse ratio. At higher load conditions, the fuel-air-pulse ratio increases significantly and leads to a deeper penetration of the fuel jets in the middle flow channel.

An essential feature of the present invention is that the outlet openings of the discrete fuel injections are set in the circumferential direction ( see FIGS. 10, 12 ). The angle of attack of the fuel jets in the circumferential direction should be in the range between 10 ° ≤ δ2 ≤ 60 °. This can be by a - in relation to the twisted air flow of the central air passage 15 - the same direction or opposite directions. Generally, the fuel jets may be at individual angles δ2. Due to the circumferential setting of the fuel jets is compared to a non-twisted injection with δ2 = 0 ° achieved a significant reduction in the penetration depth of the jets, which leads to a given number of injection points on the one hand to homogenization of the fuel-air mixture in the periphery and on the other hand, a radial boundary Fuel placement near the inner surface of the main fuel injection result. The fuel jets can continue to be employed with respect to the burner axis 4 in the axial direction. The preferred axial angle of attack of the fuel jets is in the range between -10 ° ≤ δ1 ≤ 90 °. As with the circumferential adjustment, the fuel jets can be set at individual angles δ1. The recesses can also be made individually (both with respect to δ1 and δ2).

At low to medium load conditions, the effects described above lead to an improvement of the combustion chamber burnout as a result of local fuel enrichment. At higher load conditions up to full load conditions, a higher penetration depth of the jets arises due to a higher fuel pressure and thus also higher fuel speed of the individual jets. The associated intensification of the jet dispersion results in a given circumferential adjustment of the fuel jets to a further homogenization of the fuel-air mixture in the radial direction and circumferential direction. With this method of the strong employment of the fuel jets δ1, δ2 can be set under high load conditions lean air-fuel ratios.

• In Fig. 9 ist in einer Querschnittsdarstellung eine berechnete Umfangsverteilung der Kraftstoff-Luft-Mischung für die Anwendung von stark angestellten Kraftstoffstrahlen für die Hauptstufe gezeigt. Es sind lokal magere Gemische 32 sowie im Bereich der Strahleindringung in den mittleren Strömungskanal lokal kraftstoffangereicherte Zonen 31 zu erkennen. Neben der Zumessung des Kraftstoffs über Bohrungen an oder nahe der Oberfläche der Hauptkraftstoffeinspritzung 38, 19 besteht ein weiteres Merkmal der vorliegenden Erfindung in der Zumessung des Kraftstoffs für die Hauptstufe weiter stromauf in der Kraftstoffpassage. Eine gegenüber der diskreten Kraftstoffeindüsung für die Hauptstufe geänderte Kraftstoffplatzierung über einen Filmspalt im Austritt der Kraftstoffpassage ist in Fig. 8 dargestellt. Über diskrete Kraftstoffbohrungen 41 wird der Hauptkraftstoff zunächst stromauf der Austrittsfläche der Kraftstoffpassage zugemessen (siehe Fig. 13). Sowohl die Anzahl der Bohrungen n als auch die Umfangsanstellung der Bohrungen δ2 entsprechen hierbei den bereits beschriebenen Parameterbereichen für den Fall der Integration der Kraftstoffbohrungen an oder nahe der inneren Oberfläche der Hauptkraftstoffeinspritzung 19, 38. Über eine geeignete Strömungsführung durch ein inneres und äußeres Wandelement der Kraftstoffpassage 40, 43 wird ein Teil des Kraftstoffimpulses bereits vor dem Einspritzen in den mittleren Strömungskanal 15 abgebaut. Ziel ist die Erzeugung eines Kraftstofffilms mit in Umfangsrichtung kontrolliert einstellbaren Kraftstoffinhomogenitäten (ähnlich zu der in Fig. 9 gezeigten Kraftstoff-LuftVerteilung).

Controlled fuel inhomogeneity through a fuel film with local fuel enrichment:

• In Fig. 9 Figure 3 is a cross-sectional view showing a calculated circumferential distribution of the fuel-air mixture for the application of high-powered fuel jets to the main stage. Locally lean mixtures 32 as well as locally fuel-enriched zones 31 can be recognized in the region of the jet penetration into the middle flow channel. In addition to metering the fuel through wells at or near the surface of the main fuel injection 38, 19, another feature of the present invention is the metering of fuel for the main stage further upstream in the fuel passage. A fuel placement over a film gap in the exit of the fuel passage changed in relation to the discrete fuel injection for the main stage is in Fig. 8 shown. About discrete fuel holes 41 is the Main fuel is first metered upstream of the exit surface of the fuel passage (see Fig. 13 ). Both the number of holes n and the circumferential setting of the bores δ2 correspond to the parameter ranges already described for the case of the integration of the fuel bores at or near the inner surface of the main fuel injection 19, 38. Via a suitable flow guidance through an inner and outer wall element of the fuel passage 40, 43, part of the fuel pulse is already reduced before being injected into the middle flow channel 15. The aim is to produce a fuel film with circumferentially controlled adjustable fuel inhomogeneities (similar to those in Fig. 9 shown fuel-air distribution).

This can be realized by two different methods. The first method is to meter the main fuel through discrete fuel bores upstream of the main fuel passage exit face and directly adjust a circumferentially controlled inhomogeneous fuel-air mixture. This can be achieved by a suitable choice of the number, arrangement and adjustment of the fuel bores and by ensuring a low interaction of the injected fuel jets with the wall element already described within the fuel level. This means that the fuel jets injected into the middle flow channel still have a defined velocity pulse. While the fuel film for known film laying concepts has almost no fuel pulse, due to the flow guidance, the short run length of the main fuel between the inner surface of the main stage 19, 38 and the location of the holes 41 is a load-dependent penetration depth of a more or less closed fuel film, albeit reduced or to a fuel film approximated fuel entry adjustable.

For metering the fuel via discrete recesses, upstream of an exit face of a main fuel line and to produce a fuel film with defined fuel strands additional wall elements downstream of the film gap, e.g. Turbulators / turbulators, lamella geometries, etc., provided, which lead to a formation of fuel inhomogeneities in the circumferential direction.

As another method for adjusting circumferentially inhomogeneity of the fuel-air mixture, a "subsequent" local enrichment of the fuel film in the circumferential direction is proposed when using a fuel film ( Fig. 19 ). These inhomogeneities in the fuel distribution can be achieved by different measures, for example of turbulators placed on the film laying surface, a suitable design of the trailing edge of the film layer (eg corrugated arrangement, lamella shape). The said methods for local adjustment of inhomogeneities for the fuel film can be located both within the middle flow channel both upstream and / or downstream of the film gap.

Furthermore, according to the invention is preferably provided to provide the arrangement of the turbulators on the surface of the film layer as follows: upstream or downstream of the film gap, then each 1-row or multi-row, with / without circumferential position, but also a circumferentially closed ring geometry of the turbulator (eg circumferential edge / step).

• Ein wesentliches Merkmal der vorgeschlagenen Erfindung ist weiterhin die Intensivierung des Strahlzerfalls der diskreten Einzelstrahlen bzw. des Filmzerfalls eines im Umfang kontrolliert inhomogenen Kraftstofffilms zur Reduktion der mittleren Tropfendurchmesser des erzeugten Kraftstoffsprays. Dies soll durch die Einspritzung des Hauptkraftstoffs in Strömungsgebiete mit hoher Strömungsgeschwindigkeit im mittleren Luftkanal verwirklicht werden 36. Der Flammenstabilisator 24, der sich zwischen der Pilot- und der Hauptstufe befindet, ist mit einem an die Geometrie der Hauptstufe angepassten äußeren Umlenkring (Schenkel) versehen 26. Dieser Umlenkring ist in Bezug zur Brennerachse mit einem definierten Winkel angestellt, wobei der Anstellwinkel α zwischen 10° und 50° liegen kann. Eine weitere Maßnahme zur Strömungsbeschleunigung im Nachlauf der Schaufeln für den mittleren Luftkanal ist das Vorsehen eines definierten Anstellwinkels für die innere Wand der Hauptstufe 19. Dieser Anstellwinkel liegt - bezogen auf die nicht abgelenkte Hauptströmungsrichtung - im Bereich zwischen 5° ≤ β ≤ 40° (siehe Fig. 11). Die beschriebenen Methoden - Anstellung des äußeren Umlenkrings, und Anstellung der inneren Wand der Hauptstufe - führen zu einer deutlichen Beschleunigung der Luftströmung im mittleren Luftkanal im Nachlauf der Schaufeln. Der Strömungskanal ist so ausgelegt, dass sich das Gebiet der höchsten Strömungsgeschwindigkeiten nahe der Eindüsung des Hauptkraftstoffs befindet.

Methods for increasing the air velocity in the middle flow channel:

• An essential feature of the proposed invention is also the intensification of the jet disintegration of the discrete individual beams or of the film decay of a controlled in the range of inhomogeneous fuel film for reducing the average Drop diameter of the generated fuel spray. This is to be achieved by the injection of the main fuel into flow areas with high flow velocity in the middle air duct 36. The flame stabilizer 24, which is located between the pilot and the main stage, is provided with an outer deflection ring (leg) adapted to the geometry of the main stage 26 This deflection ring is set with respect to the burner axis with a defined angle, wherein the angle of attack α can be between 10 ° and 50 °. Another measure for the flow acceleration in the wake of the blades for the middle air duct is the provision of a defined angle of attack for the inner wall of the main stage 19. This angle is - based on the undeflected main flow direction - in the range between 5 ° ≤ β ≤ 40 ° (see Fig. 11 ). The methods described - employment of the outer deflection ring, and employment of the inner wall of the main stage - lead to a significant acceleration of the air flow in the middle air duct in the wake of the blades. The flow channel is designed so that the area of the highest flow velocities is close to the injection of the main fuel.

• Ein weiteres Merkmal der vorliegenden Erfindung ist die geeignete konstruktive Gestaltung der äußeren Brennerrings 27. Die innere Kontur der Ringgeometrie 28 ist so ausgelegt, dass in Abhängigkeit von der Anstellung der äußeren Wand der Hauptstufe 20 unter keinen Betriebsbedingungen ein Abreißen der Luftströmung im äußeren Luftkanal eintritt (siehe Fig. 11). Damit soll eine möglichst verlustreduzierte Strömung ohne Strömungsrezirkulation im Nachlauf des äußeren Luftdrallerzeugers 13 gewährleistet werden. Weiterhin ist die Profilierung der inneren Kontur der Ringgeometrie so gewählt, dass ein hoher Luftanteil aus dem äußeren Strömungskanal für die Kraftstoff-Luft-Mischung der Hauptkraftstoffeinspritzung bereitgestellt wird.

Methods to avoid a stall in the outer flow channel and to improve the fuel economy of the main injection:

• Another feature of the present invention is the appropriate structural design of the outer burner ring 27. The inner contour of the ring geometry 28 is designed so that depending on the employment of the outer wall of the main stage 20 under any operating conditions tearing of the air flow in the outer air channel occurs ( please refer Fig. 11 ). This is to ensure a possible loss-reduced flow without flow recirculation in the wake of the outer air swirler 13. Furthermore, the profiling the inner contour of the ring geometry is selected so that a high proportion of air from the outer flow channel for the fuel-air mixture of the main fuel injection is provided.

• Um neben einer Verbesserung des Brennkammerausbrandes auch eine Senkung der Schadstoffemissionen über einen weiten Lastbereich zu erreichen, erscheint die Einstellung einer gemischten und/oder lastabhängigen Strömungsform mit einer definierten Interaktion der Pilot- und Hauptflamme als vorteilhaft. Eine zu starke Separation der Pilot- und Hauptflamme soll vermieden werden. Generell wird erwartet, dass eine starke Separierung beider Zonen zu einem verbesserten Betriebsverhalten des Brenners führen kann, wenn vorzugsweise die Pilot- bzw. die Hauptstufe betrieben wird. Dies ist z.B. der Fall im unteren Lastbereich (nur die Pilotstufe wird mit Kraftstoff versorgt) und im Hochlastbetrieb (der überwiegende Anteil des Kraftstoffs wird auf die mager operierende Hauptstufe verteilt). Allerdings kann dadurch über einen weiten Teil des Betriebsbereiches, insbesondere im Teillastbereich (z.B. Reiseflugbedingung, Stufungspunkt), eine Verminderung des Brennkammerausbrandes stattfinden, da ein vollständiger Ausbrand des Kraftstoffs für die mit hohem Luftüberschuss operierende Hauptstufe kritisch ist. Aus diesem Grund wird eine kontrollierte Interaktion beider Verbrennungszonen angestrebt, um mit Hilfe der heißen Verbrennungsgase der Pilotstufe eine Temperaturerhöhung in der Hauptreaktionszone zu bewirken.

Contoured flame stabilizer, fixed geometry:

• In order to achieve a reduction of pollutant emissions over a wide load range in addition to an improvement of the Brennkammerausbrandes, the setting of a mixed and / or load-dependent flow form with a defined interaction of the pilot and main flame appears to be advantageous. Too much separation of the pilot and main flame should be avoided. In general, it is expected that a strong separation of both zones can lead to an improved performance of the burner, if preferably the pilot or the main stage is operated. This is the case, for example, in the lower load range (only the pilot stage is fueled) and in high load mode (the majority of the fuel is distributed to the lean main stage). However, this can take place over a large part of the operating range, in particular in the partial load range (eg cruising condition, staging point), a reduction of Brennkammerausbrandes, since a complete burnout of the fuel for the operating at high excess air main stage is critical. For this reason, a controlled interaction of both combustion zones is sought in order to bring about a temperature increase in the main reaction zone with the aid of the hot combustion gases of the pilot stage.

Provided according to the invention are different geometries for flame stabilizers 24, which enable the defined setting of a flow field with pronounced properties of centralized and decentralized recirculation. In general, a specific contouring, both in the axial and in the circumferential direction, of the flame stabilizer is proposed. An embodiment with a flower-shaped geometry for the outlet cross-section of a flame stabilizer is in Fig. 14 shown. The diameter of the exit surface varies between a minimum diameter A1, which can lead to a pronounced decentralized recirculation in the wake of the V-shaped flame stabilizer, and a maximum diameter A2, which favors the formation of a central recirculation on the burner axis. In particular, by the circumferential variation of the outlet diameter A of the flame stabilizer is expected that both a central and decentralized recirculation can be targeted.

In addition to the in Fig. 14 illustrated variant for a contoured flame stabilizer with 8 so-called "flowers" are proposed further variants, the proposed geometries between 2 and 20 "flowers" may have. In Fig. 15 Another version is shown for a slightly more contoured flame stabilizer with 8 "flowers" in which the diameter A1 is reduced and at the same time the diameter A2 is increased. Thus, the flow locally undergoes a flow acceleration or delay, resulting in a highly three-dimensional flow area with both centralized and decentralized recirculation (see Fig. 5 ).

A further embodiment provides for the circumferential alignment of the 3D wave geometry (contours) of the flame stabilizer at the effective helix angle of the deflected air flow for the inner pilot stage and / or the effective helix angle of the deflected air flow for the radially outer main stage.

In Fig. 16 another embodiment of the contoured flame stabilizer is shown. The contouring of the inner leg of the flame holder has 5 flowers, whereby by the number and arrangement of the flowers a diameter variation is achieved with a controlled asymmetry in the flow guidance of the pilot flow. Thus, both a strong flow acceleration as well as due to the cross-sectional widening a deflection and flow delay is implemented in a sectional plane. Regarding the adjustable asymmetry in the pilot flow is in Fig. 17 another embodiment of a flame stabilizer with an eccentric positioning shown. An additional option for contouring 25 is a sawtooth profile.

Another feature of the present invention with respect to the design of the flame stabilizer, in addition to the described contouring of the inner leg 25 is a contouring of the outer leg of the flame stabilizer 26, wherein the proposed for the inner leg of the flame stabilizer geometries can also be used for the outer leg 26.

• Zur kontrollierten Einstellung eines Strömungsfeldes mit unterschiedlichen Rückströmzonen wird neben einer geometrisch festen Geometrie eines konturierten Flammenstabilisators eine variable Geometrie vorgeschlagen. Der Vorteil einer variablen Geometrie ist, dass in Abhängigkeit vom Lastzustand eine gewünschte Strömungsform in der Brennkammer eingestellt werden kann und somit das Betriebsverhalten des Brenners hinsichtlich Schadstoffreduktion, Ausbrand und Flammenstabilität positiv beeinflusst werden kann. Als eine Möglichkeit zur Anpassung des Strömungsfeldes mit Hilfe einer variablen Geometrie für den Flammenstabilisator wird z.B. die Integration von Piezo-Elementen als Zwischenelement oder direkt an der Hinterkante des inneren oder äußeren Schenkels des Flammenstabilisators vorgeschlagen. Bei diesen Elementen soll das Prinzip der spannungsabhängigen Feldausdehnung ausgenutzt werden. Dies bedeutet, dass im Originalzustand, d.h. ohne Spannungsbelastung der Piezo-Elemente, ein vergrößerter Austrittsquerschnitt des Flammenstabilisators vorhanden ist. Dieser Zustand entspricht dem Vorhandensein eines vergrößerten Austrittsdurchmessers A2, der das Ausbilden einer vorwiegend dezentralen Rezirkulationszone begünstigt. Bei Anlegen eines Spannungszustandes tritt eine Materialausdehnung mit einer radialen Komponente in Richtung Brennerachse auf (siehe Fig. 18). Dies führt zu einem kleinen Austrittsquerschnitt und in Kombination mit einem erniedrigten Luftdrall für die Pilotstufe zur Generierung eines ausgeprägten Rückströmgebietes im Nachlauf des Flammenstabilisators. Dies führt u.a. zu einer deutlichen Verbesserung der Flammenstabilität hinsichtlich einer Verlöschung bei magerem Betrieb des Brenners.

Contoured flame stabilizer, variable geometry:

• For the controlled adjustment of a flow field with different backflow zones, a variable geometry is proposed in addition to a geometrically fixed geometry of a contoured flame stabilizer. The advantage of a variable geometry is that, depending on the load condition, a desired flow pattern can be set in the combustion chamber, and thus the performance of the burner with respect to pollutant reduction, burnout and flame stability can be positively influenced. As one way to adapt the flow field using a variable geometry for the flame stabilizer, for example, the integration of piezo elements as an intermediate element or directly to the trailing edge of the inner or outer leg of the flame stabilizer is proposed. These elements should exploit the principle of voltage-dependent field expansion. This means that in the original state, ie without stress of the Piezo elements, an enlarged outlet cross-section of the flame stabilizer is present. This condition corresponds to the presence of an increased exit diameter A2, which favors the formation of a predominantly decentralized recirculation zone. When a stress state is applied, a material expansion with a radial component occurs in the direction of the burner axis (see Fig. 18 ). This leads to a small outlet cross-section and in combination with a reduced air swirl for the pilot stage to generate a pronounced return flow region in the wake of the flame stabilizer. This leads, inter alia, to a significant improvement in the flame stability with respect to a quenching during lean operation of the burner.

As another principle of variably adjusting the flow shape by adjusting the exit geometry of the flame stabilizer, the implementation of bimetal elements in the geometry of the flame holder is proposed. The principle of temperature-dependent material expansion is used. For example, bimetal elements can be integrated into the front part of the flame stabilizer or at the trailing edge of the flame stabilizer to achieve a desired change in exit geometry.

• Der wesentliche Vorteil der vorliegenden Erfindung liegt in der kontrollierten Einstellung der Kraftstoff-Luft-Mischung für die Hauptstufe eines mager betriebenen Brenners. Durch das Vorhandensein lokal fetter Gemische kann mit den beschriebenen Maßnahmen ein ausreichend hoher Brennkammerausbrand insbesondere bei niedrigen bis mittleren Lastbedingungen erreicht werden. Über die Anstellung der Kraftstoffstrahlen (insbesondere im Umfang) kann zudem bei Hochlastbedingungen eine im Umfang verbesserte Kraftstoff-Luft-Mischung erzielt werden, so dass ähnlich zu einem optimierten Filmleger sehr geringere NOx-Emissionen entstehen.

Advantages of the invention:

• The essential advantage of the present invention lies in the controlled adjustment of the fuel-air mixture for the main stage of a lean-burn burner. Due to the presence of locally rich mixtures, a sufficiently high combustion chamber burnout can be achieved with the measures described, in particular at low to medium load conditions. The employment of the fuel jets (especially in the scope) can also be achieved under high load conditions to a much improved air-fuel mixture, so that similar to an optimized film depositor very low NOx emissions arise.

Another advantage of the invention is the possibility of controlled adjustment of a "mixed" flow field with distinct central and decentralized recirculation areas. It is expected that the presence of a central recirculation on the one hand, the NOx emissions can be significantly reduced and can be achieved by setting a sufficient Rückströmzone in the wake of the flame stabilizer very high flame stability against lean burn. Furthermore, it is expected that the interaction between the pilot and main flame can be more controlled, since depending on the 3D contour of the flame stabilizer there is the possibility to generate different flow states with more or less strong interaction of the pilot and main flow. With the help of this targeted generation of a "mixed" flow form, the operating range of the lean burn burner can be significantly extended between low and full load.

Another advantage of the invention is expected in the field of ignition of the pilot stage. Due to the contoured geometry of the exit surface with locally increased pitch diameters A2, a radial expansion (dispersion) of the pilot spray is generated, which can lead to improved mixture preparation. This increases the likelihood that a greater part of the pilot spray can be brought into the vicinity of the combustion chamber wall in the region of the spark plug and thus - depending on the local fuel-air mixture - the ignition characteristics of the burner can be improved. Another advantage of the three-dimensional contouring of the flame stabilizer is an equalization of the flow and thus the reduction of the occurrence of possible flow instabilities, which can often form in the wake of bluff bodies - especially in the shear layer.

The advantage of a variable adaptation of the outlet cross section of the flame stabilizer and thus ultimately the adjustment of the flow velocity is the possibility of "automatically" set central or decentralized recirculation zones within the combustion chamber as a function of the current operating state. Using this method, it would be possible to generate a central flow recirculation on the burner axis in a certain operating range, which favors the reduction of NOx emissions, particularly in the high load range, due to the "opening up" of the pilot flow and the corresponding interaction between the pilot and main flame. On the other hand, a high flame stability in the lower load range can be achieved by favoring a significant increase in the flow rate by reducing the exit area of the flame stabilizer. This enables targeted optimization of the burner behavior for different operating states.

LIST OF REFERENCE NUMBERS

1

fuel nozzle

2

combustion chamber

3

combustor flow

4

Brenner

5

central recirculation area

6

Rezirkulationsgebiet in the wake of the flame stabilizer

7

Fuel input for the main stage

8th

Fuel input for the pilot stage

9

Fuel-air mixture of the main stage

10

Fuel-air mixture of the pilot stage

11

inner air swirl generator

12

medium air swirl generator

13

outer air swirl generator

14

inner flow channel

15

medium flow channel

16

outer flow channel

17

Pilot fuel injection

18

Main fuel injection

19

inner downstream surface of the main fuel injection, film layer

20

outer surface of the main fuel injection

21

Trailing edge of the main fuel injection

22

Exit slit of the main fuel injection

23

Outlet holes of the main fuel injection

24

flame stabilizer

25

inner leg of the flame stabilizer

26

outer leg of the flame stabilizer

27

outer burner ring (dome)

28

inner contour of the outer burner ring

29

Pilot fuel supply

30

Main fuel supply

31

locally rich fuel-air mixture

32

locally lean fuel-air mixture

33

Exit surface of the pilot fuel injection

34

Outlet contour of the inner leg of the flame stabilizer

35

Bi-metal elements

36

Flow in the wake of the middle swirl generator

37

accelerated velocity region on the burner axis

38

inner upstream surface of the main fuel injection

39

Fuel passage of the main fuel injection

40

outer wall element of the fuel passage of the main injection

41

Alternative metering of the main fuel via upstream holes

42

Fuel film with local fuel enrichment in the axial and / or circumferential direction

43

inner wall element of the fuel passage of the main injection

44

Turbulator element for generating local fuel inhomogeneities on the film former

45

Fuel film with low fuel inhomogeneities in the circumferential direction

Claims (19)

A gas turbine lean burn burner having a combustion chamber (2) and a fuel nozzle (1) comprising a pilot fuel injection (17) and a main fuel injection (18), characterized in that the main fuel injection (18) comprises central inhomogeneous fuel injection controlled recesses (23) primarily in the circumferential direction whose number on the circumference between 8 and 40 and which have a pitch angle δ2 in the circumferential direction of 10 ° ≤ δ2 ≤ 60 ° and an axial angle δ1 relative to the burner axis (4) between -10 ° ≤ δ1 ≤ 90 °. Gasturbinenmagerbrenner according to claim 1, characterized in that the recesses (23) are arranged in a single-row arrangement. Gas turbine lean burn burner according to claim 1, characterized in that the recesses (23) are arranged in a multi-row arrangement. Gas turbine lean burn burner according to claim 1, characterized in that the recesses (23) are arranged in a staggered arrangement. Gasturbinenmagerbrenner according to one of claims 1 to 4, characterized in that for metering the fuel via discrete recesses upstream of an exit surface of a main fuel line and to produce a fuel film with defined fuel strands a plurality of recesses are provided, the number is between 8 and 40 and the angle of attack δ2 in the circumferential direction between 10 ° ≤ δ2 ≤ 60 °. Gasturbinenmagerbrenner according to one of claims 1 to 5, characterized in that for metering the fuel via discrete recesses upstream of an exit surface of a main fuel line and to produce a fuel film with defined fuel strands additional wall elements are provided downstream of the film gap, leading to a formation of fuel inhomogeneities in the circumferential direction , Gasturbinenmagerbrenner according to one of claims 1 to 6, characterized by a V-shaped flame stabilizer (24) having an inner leg (25) which is contoured in the axial direction and in the circumferential direction and comprises 2 to 20 circumferentially arranged contours of a flower shape. Gasturbinenmagerbrenner according to claim 7, characterized in that the contours of the flower shape are distributed uniformly around the circumference. Gasturbinenmagerbrenner according to claim 7, characterized in that the contours of the flower shape are distributed unevenly around the circumference. Gasturbinenmagerbrenner according to claim 7, characterized in that the contours of the flower shape are distributed with an eccentricity of the exit geometry relative to the burner axis on the circumference. Gasturbinenmagerbrenner according to one of claims 1 to 10, characterized in that an outer leg (26) of the V-shaped flame stabilizer (24) is contoured in the axial direction and in the circumferential direction with 2 to 20 circumferentially arranged contours of a flower shape. Gas turbine lean burn burner according to claim 11, characterized in that the contours of the flower shape are distributed uniformly around the circumference. Gasturbinenmagerbrenner according to claim 11, characterized in that the contours of the flower shape are distributed unevenly around the circumference. Gasturbinenmagerbrenner according to claim 11, characterized in that the contours of the flower shape are distributed with an eccentricity of the exit geometry relative to the burner axis on the circumference. Gas turbine lean burn burner according to one of claims 1 to 14, characterized by a V-shaped flame stabilizer (24) which is provided on an inner leg (25) and / or on an outer leg (26) with a variable geometry. Gasturbinenmagerbrenner according to one of claims 1 to 15, characterized in that a main stage of the fuel injection between 5 ° and 60 ° to the burner axis (4) is employed. Gas turbine lean burn burner according to one of claims 1 to 16, characterized in that turbulator elements (44) are arranged on the surface of the film applicator. Gas turbine lean burn burner according to claim 17, characterized in that the turbulator elements (44) are arranged upstream of the film gap. Gas turbine lean burn burner according to claim 17, characterized in that the turbulator elements (44) are arranged downstream of the film gap.

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