EP2587158A1 - Combustion chamber for a gas turbine and burner assembly - Google Patents

Abstract

The invention relates to a combustion chamber (10, 20) for a gas turbine (1) having at least one combustion zone (23, 24) and at least one burner arrangement (11, 28) for combustion of a fuel / air mixture in the combustion zone (23, 24). in which the burner arrangement (11, 28) comprises at least one premix passage (29) discharging into the combustion zone (23, 24) to provide a fuel / air mixture, and into the premix passage (29) one from the burner arrangement (11, 28). enclosed air supply (32) and at least one fuel supply (33) opens.

The combustion chamber allows a particularly effective damping of combustion chamber pressure fluctuations.

For this purpose, the air supply (32) is stepped, so that different delay times (τ ₁ , τ ₂ , τ ₃ ) are assignable to the premixed passage (29) opening outlet openings (34, 34 a, 34 b, 34 c) of the stepped air supply.

Description

The invention relates to a combustion chamber for a gas turbine having at least one combustion zone and at least one burner arrangement for combustion of a fuel / air mixture, wherein the burner arrangement comprises at least one premix passage opening into the combustion zone for providing a fuel / air mixture, and into the premix passage from the burner assembly included air supply and at least one fuel supply opens.

The invention also relates to a gas turbine with such a combustion chamber and to a burner assembly.

Known gas turbines comprise, in addition to an initially mentioned combustion chamber, a compressor and a turbine. The compressor compresses the gas supplied to the gas turbine, a portion of this air is used to burn fuel in the combustion chamber and a part is used to cool the gas turbine and / or the combustion gases. The hot gases provided by the combustion process in the combustion chamber are introduced into the turbine from the combustion chamber, where they relax and cool, causing turbine blades to rotate under the action of work. By means of this rotational energy, the gas turbine drives a work machine. The work machine may be, for example, a generator.

The fuel / air mixture provided by the at least one burner assembly is premixed in the at least one premix passage to then be ignited after flowing into the combustion zone. The premixing of the fuel with the air reduces the pollutant emissions produced during the combustion, in contrast to the previously customary direct injection of the fuel into the combustion zone. A disadvantage of the premix of the fuel However, this arrangement is much more susceptible to the formation of combustion chamber pressure fluctuations. If there are pressure fluctuations in the combustion zone, there are also concentration fluctuations in the fuel / air mixture in the premix passage, which lead to heat release fluctuations during combustion. These thermoacoustic instabilities in turn increase the combustion chamber pressure fluctuations, wherein there are preferred frequencies in the arrangement for these aufschaukelnden combustion chamber pressure fluctuations. The concentration variations in the fuel / air mixture, ie temporal variations in the air-fuel mixture ratio, may also be referred to as air frequency fluctuations. The air frequency fluctuations result from different acoustic resistances of the air supply and fuel supply. For damping the combustion chamber pressure fluctuations, known gas turbines comprise resonators arranged in the housing. Since the resonators are directly adjacent to the combustion zone and also interrupt a heat shield arrangement in the housing and therefore have to be cooled, such a design of the combustion chamber is expensive. An alternative embodiment of a known combustion chamber provides for suppression of such combustion chamber pressure fluctuations that the fuel nozzles opening into the premix passage are distributed along the premix passage in the axial direction, so that mixing zones with different delay times are formed in the premix passage. This staged design of the fuel supply makes it possible to mitigate the fluctuations in concentration caused by the combustion chamber pressure fluctuation in the fuel injected by the fuel supply. The fuel nozzles may also be referred to with outlet openings of the fuel supply.

The object of the invention is to provide a combustion chamber of the aforementioned type and a gas turbine with such a combustion chamber and a burner arrangement comprising such a combustion chamber, which enables a particularly effective damping of combustion chamber pressure fluctuations.

The object is achieved according to the invention in a combustion chamber of the type mentioned above in that the air supply is stepped, so that different delay times can be assigned to the outlet opening of the stepped air supply opening into the premix passage.

By the known fuel supply with along the Vormischpassage distributed in the axial direction arranged fuel nozzles can be offset by combustion chamber pressure fluctuations caused fluctuations in the amount of fuel, which is mixed with the air flow along the Vormischpassage. However, due to the different acoustic resistances of the air and of the fuel, this known graduation can not inject the fuel into the air stream in such a way that a constant ratio of fuel and air and a constant amount of fuel per time out of the premix passage and into the combustion zone. According to the invention, therefore, for suppressing combustion chamber pressure fluctuations and thus also heat release fluctuations, it is proposed to design the air supply opening into the premix passage and thus to mitigate the density fluctuations caused by combustion chamber pressure fluctuations in the air flow passing through the premix passage. Due to the high compressibility of the air compared to, for example, liquid fuel and the lower pressure in the air supply line compared to the pressure in the fuel supply line, this is particularly effective for suppressing combustion chamber pressure fluctuations.

According to the invention, the stepped air supply comprises outlet openings which open into the premix passage and to which different delay times can be assigned. The stepped air supply may further comprise further outlet openings, which redundant delay times can be assigned. The delay time can also be referred to as convective time delay. It is determined by the time it takes for a fluid element entering the premix passage to travel to the combustion zone to get. The outlet openings can also be referred to with outlet openings.

For example, the burner assembly may include a pilot burner having a premix passage with a pilot burner lance centrally disposed therein, the pilot burner lance connected to a fuel supply and including fuel nozzles. In the premix passage of the pilot burner opens an air supply. Around the pilot burner, a plurality of main mixers included in the burner assembly can be arranged. Each of the main mixers may comprise a premix passage comprised of a cylindrical housing, into which an air feed opens, and in which is axially arranged a fuel nozzle lance connected to a fuel supply. The lance can be supported, for example via swirl blades on the housing. According to the invention, at least one of the premix passages in the exemplified burner arrangement comprises a stepped air feed. For example, in each case the air supply of the main mixer can be formed stepped by the swirl blades form in the premix passage opening air outlet openings, which different delay times can be assigned. These can preferably be selected such that, at least in the frequency range of a preferred combustion chamber pressure fluctuation, density fluctuations in the supplied air caused by these are canceled or reduced by means of the different delay times of the air outlet openings.

An advantageous development of the invention can provide that in addition to the stepped air supply formed in the premix passage and can be acted upon with gaseous fuel supply also formed stepwise.

Since the gaseous fuel also has a high compressibility compared to air, can be through the additional grading of gaseous fuel acted upon fuel supply by combustion chamber pressure fluctuations caused fluctuations in the concentration and density of the flowing from the Vormischpassage into the combustion zone fuel / air mixture even more effectively attenuate. If the premix passage comprises more than one fuel feed which can be acted upon by gaseous fuel, one or more of these fuel feeds which can be acted upon by gaseous fuel can be designed in a stepped manner.

Advantageously, it can further be provided that delay times can be assigned to the outlet openings of the stepped feed, wherein for a minimum delay time τ _min and a maximum delay time τ _max with respect to a suppressible combustion chamber pressure fluctuation of the frequency f: τ _max -τ _min > 1 / f.

The condition ensures that, at least in the frequency range of the combustion chamber pressure fluctuation to be suppressed, density fluctuations caused thereby in the fluid supplied by the stepped supply are effectively attenuated. The stepped feeder is the stepped air supply. If further feeds leading into the premix passage are formed in a stepped manner, the condition can also apply to these feeds. The minimum and maximum delay time specified in the condition refers to the shortest or the longest of the delay times associated with the outlet ports of a feeder.

It may also be considered advantageous that the outlet ports of the stepped supply opening into the premix passage are arranged such that density fluctuations caused by at least one preferred combustion chamber pressure fluctuation of the frequency f 'in the fluid supplied through the outlet openings in the premix passage due to the outlet openings assigned different delay times superimpose such that they essentially cancel each other out.

According to an advantageous development of the invention it can be provided that the burner arrangement is arranged in the region of a second axial stage with at least one premix passage opening into the combustion zone, the combustion zone following downstream of a first combustion zone with a first burner arrangement.

By means of a second axial stage, the heat release over the entire available combustion chamber can be further distributed, so that the tendency of the combustion system to thermoacoustic instabilities is further reduced. In addition, a stepped air supply to at least one premix passage of the burner arrangement of the second axial stage is particularly easy to implement in terms of apparatus.

A preferred embodiment of the invention can provide that the burner arrangement comprises a fuel distributor ring disposed outside a combustion chamber housing and a multiplicity of premix passage, wherein the premix passages open into the combustion chamber with their one end into the combustion chamber and with at least one fuel feed branching off from the fuel distributor ring correspond, wherein at least along one of the Vormischpassagen outlet openings of a stepped air supply are arranged distributed.

This stepped air supply to at least one premix passage of the burner assembly of the second axial stage is particularly easy to implement in terms of apparatus. The premixing passages may, for example, have a tubular design, wherein the situation of the air outlet openings along the premixing passages or the corresponding delay times relative thereto may be adaptable to the frequency of the combustion chamber pressure fluctuations to be suppressed. For example, the tubular Vormischpassage consist of an elastic material whose length - and thus also the corresponding to the outlet openings delay times - is adaptable to a frequency to be suppressed.

Another object of the invention is to provide a gas turbine with at least one combustion chamber mentioned above, which allows a particularly effective damping of combustion chamber pressure fluctuations.

For this purpose, the gas turbine on at least one combustion chamber, which is designed according to one of claims 1 to 6.

A further object of the invention is to specify a burner arrangement encompassed by the initially mentioned combustion chamber, which enables a particularly effective damping of combustion chamber pressure fluctuations.

For this purpose, the burner assembly is part of the combustion chamber according to one of claims 1 to 6.

Further expedient refinements and advantages of the invention are the subject matter of the description of embodiments of the invention with reference to the figure of the drawing, wherein like reference numerals refer to the same acting components.

Fig.1

eine schematische Schnittansicht einer Gasturbine nach dem Stand der Technik,

Fig.2

einen Ausschnitt einer Brennkammer mit zweiter axialer Stufe gemäß einem Ausführungsbeispiel der Erfindung in einer schematischen Schnittansicht, und

Fig.3

eine Detailansicht des in Figur 2 dargestellten Ausführungsbeispiels im Bereich der gestuften Luftzuführung in einer schematischen Schnittansicht.

It shows the

Fig.1

a schematic sectional view of a gas turbine according to the prior art,

Fig.2

a section of a combustion chamber with second axial stage according to an embodiment of the invention in a schematic sectional view, and

Figure 3

a detailed view of the in FIG. 2 illustrated embodiment in the region of the stepped air supply in a schematic sectional view.

The FIG. 1 shows a schematic sectional view of a gas turbine 1 according to the prior art. The gas turbine 1 has inside a rotatably mounted about a rotation axis 2 rotor 3 with a shaft 4, which is also referred to as a turbine runner. Along the rotor 3 successively follow an intake housing 6, a compressor 8, a combustion system 9 with a number of combustion chambers 10, each comprising a burner assembly 11 and a combustion chamber housing 12, a turbine 14 and an exhaust housing 15th

The combustion system 9 communicates with an annular hot gas duct, for example. There, a plurality of successively connected turbine stages form the turbine 14. Each turbine stage is formed of blade rings. Viewed in the flow direction of a working medium follows in the hot runner formed by a number 17 vanes row formed from blades 18 row. The guide vanes 17 are fastened to an inner housing of a stator 19, whereas the moving blades 18 of a row are attached to the rotor 3, for example by means of a turbine disk. Coupled to the rotor 3 is, for example, a generator (not shown).

During operation of the gas turbine, air is sucked in and compressed by the compressor 8 through the intake housing 6. The compressed air provided at the turbine-side end of the compressor 8 is led to the combustion system 9 where it is mixed with a fuel in the area of the burner assembly 11. The mixture is then burned by means of the burner assembly 11 to form a working gas stream in the combustion system 9. From there, the working gas stream flows along the hot gas channel past the guide vanes 17 and the rotor blades 18. At the rotor blades 18, the working gas stream relaxes in a pulse-transmitting manner, so that the rotor blades 18 drive the rotor 3 and this coupled to him generator (not shown).

The FIG. 2 shows a section of a combustion chamber 20 of a gas turbine according to an embodiment of the invention. The combustion chamber 20 has a combustion chamber housing 21, which is rotationally symmetrical about an axis 22. In the combustion chamber housing 21 there is a first combustion zone 23 and a second combustion zone 24, the second combustion zone 24 downstream of the first combustion zone 23 with respect to a main flow direction 26. The combustor 20 includes a first burner assembly (not shown) and a second burner assembly 28 for combusting a fuel / air mixture in the second combustion zone 24. The second burner assembly 28 includes a premix passage 29 opening into the second combustion zone 24 for providing fuel / air A mixture, wherein in the Vormischpassage 29 an included from the second burner assembly 28 air supply 32 and a fuel supply 33 opens, the air supply 32 is stepped, so that the default in the Vormischpassage 29 outlet openings 34 of the stepped air supply 32 different delay times are assigned.

The second burner arrangement 28 is thus arranged in the region of a second axial step. The second burner assembly 28 includes a fuel distributor ring 36 disposed outside the combustor casing 21 and a plurality of premix passages 29, the premix passages 29 having one end 37 opening into the combustor casing 21 into the second combustion zone 24 and one each from the fuel distributor ring 36 branching fuel supply 33 correspond, wherein along at least one of the Vormischpassagen 29 outlet openings 34 of a stepped air supply 32 are arranged distributed.

According to an advantageous embodiment of the illustrated embodiment of the invention, each of the Vormischpassagen 29 of the second burner assembly 28 have a stepped air supply 32.

The fuel injected into the premix passage 29 through the fuel supply 33 mixes with the air entering the premix passage 29 through the discharge ports 34, so that a fuel / air mixture flows in the flow direction 39 along the premix passage. An air volume exiting an outlet opening 34 will mix with the fuel and will require a period of time from the position of the outlet opening 34 to enter the combustion zone 24. This period of time is referred to as the delay time and is determined by the time required for a fluid element entering the premix passage to reach the combustion zone. The outlet openings 34 arranged along the premix passage 29 correspond with different delay times due to their different arrangement in the premix passage 29. Each of the outlet openings 34 in the premix passage 29 can thus be assigned different delay times.

The FIG. 3 shows a detail view of in FIG. 2 illustrated inventive combustion chamber according to an embodiment in the region of the second burner assembly of a second axial stage. Shown is a portion of the combustor housing 21 which encloses a first combustion zone 23 (shown in part) and a second combustion zone 24 (shown in part) downstream thereof, wherein a premix passage 29 comprised by the second burner assembly provides a fuel / air mixture enters the second combustion zone 24. A fuel feed 33 for injecting fuel 35 into the premix passage 29 and an air feed 32, which is of stepped design, opens into the tubular premix passage 29. The staged air supply 32 comprises outlet openings 34a, 34b, 34c which open into the premix passage 29 for the supply of air 40, the outlet openings 34a, 34b, 34c being different Delay times τ ₁ , τ ₂ , τ ₃ , are assignable. For example, an air volume exiting from the outlet opening 34a will mix with the fuel 35 flowing past the fuel supply 33 and will require a period of time τ ₁ from the position of the outlet opening 34a to enter the second combustion zone 24. For damping or suppression of a combustion chamber pressure fluctuation of the frequency f, the position of the outlet openings 34a, 34b and 34c may advantageously be selected such that τ ₁ -τ ₃ > 1 / f. The density fluctuations of the air caused by the combustion chamber pressure fluctuation of the frequency f in the outlet openings can be superimposed upon ignition of the fuel / air mixture in the second combustion zone 24 due to the different delay times τ ₁ , τ ₂ , τ ₃ in such a way that these density fluctuations occur essentially cancel each other out. For this purpose, the arrangement of the outlet openings 34a, 34b, 34c along the premix passage 29 can be selected accordingly. The combustion chamber pressure fluctuation of the frequency f may be a combustion chamber pressure fluctuation which can preferably be excited on account of the design of the combustion chamber. This may also be referred to as preferential combustion chamber pressure fluctuation. A development of the illustrated embodiment may also provide that the fuel supply 33 is also formed stepped (not shown here).

Claims (8)

Combustion chamber (10,20) for a gas turbine (1) with - At least one combustion zone (23,24) and at least one burner arrangement (11, 28) for combustion of a fuel / air mixture in the combustion zone (23, 24), wherein the burner arrangement (11, 28) comprises at least one premix passage (29) discharging into the combustion zone (23, 24) for providing a fuel / air mixture, and one in the premix passage (29) from the burner arrangement (11, 28) comprising air supply (32) and at least one fuel supply (33) opens, characterized in that the air supply (32) is stepped, so that in the premix passage (29) opening outlet openings (34, 34a, 34b, 34c) of the stepped air supply different delay times (τ ₁ , τ ₂ , τ ₃ ) are assigned. Combustion chamber (10, 20) according to claim 1,
characterized in that in addition to the stepped air supply (32) in the Vormischpassage (29) and opening can be acted upon with gaseous fuel supply also stepped. Combustion chamber (10, 20) according to claim 1 or 2, characterized in that the outlet openings (34, 34a, 34b, 34c) of the stepped feed (32) delay times (τ ₁ , τ ₂ , τ ₃ ) are assigned, wherein for a Minimum delay time τ _min and a maximum delay time τ _max with respect to a suppressed combustion chamber pressure fluctuation of the frequency f is: τ _max - τ _min > 1 / f. Combustion chamber (10, 20) according to one of the preceding claims,
characterized in that the outlet ports (34, 34a, 34b, 34c) of the stepped supply (32) leading into the premix passage (29) are arranged such that density fluctuations caused by at least one preferred combustion chamber pressure fluctuation of the frequency f 'in the outlet openings (34a, 34b , 34c) supplied fluid in the premix passage (29) due to the outlet openings (34, 34a, 34b, 34c) associated with different delay times (τ ₁ , τ ₂ , τ ₃ ) superimpose such that they cancel each other substantially. Combustion chamber (10, 20) according to one of the preceding claims,
characterized in that the burner assembly (28) is disposed in the region of a second axial stage having at least one premix passage (29) opening into the combustion zone (24), the combustion zone (24) downstream of a first combustion zone (23) having a first burner assembly (11) follows. Combustion chamber (10, 20) according to claim 5,
characterized in that the burner assembly (28) includes a fuel distributor ring (36) disposed externally about a combustor shell (12, 21) and a plurality of premix passage (29), the premix passage (29) having one end thereof into the combustor shell (12 21) into the combustion zone (24) and correspond to at least one of the Brennstoffverteilerring (36) branching fuel supply (33), wherein at least along one of the Vormischpassagen (29) outlet openings (34, 34a, 34b, 34c) of a stepped air supply (32) are arranged distributed. Gas turbine (1) with at least one combustion chamber (10, 20), characterized in that at least one combustion chamber (20) is designed according to one of claims 1 to 6. Burner assembly (28) for a gas turbine (1), characterized in that it is part of the combustion chamber (20) according to one of claims 1 to 6.

Images