COMBUSTION CHAMBER FOR A GAS TURBINE PLANT

Abstract

A combustion chamber (1) for a gas turbine plant, has a combustion chamber wall (10), which is flowed through by combustion gases in the direction of a downstream expansion turbine, the chamber wall (10) has a device (20) for damping thermoacoustic oscillations caused by the combustion gases. At least one resonator tube (22), interacts with the resonator volume (21) and opens out into the combustion chamber (1) with its mouth (M) opposite from the resonator volume (21) in the combustion chamber inner wall (10). At least one feed opening (23, 23′, 23″) for sealing air for sealing the resonator tube mouth (M) is introduced into the combustion chamber (1) from a compressor plenum (2), surrounding the combustion chamber. The at least one first feed opening (23′, 23″) is provided in a region of the combustion chamber wall (10) close to the resonator tube mouth (M) and is aligned such that the sealing air (S) through the feed opening (23′, 23″) flows over the resonator mouth (M).

Description

The invention relates to a combustion chamber for a gas turbine plant according to the preamble of claim 1 and to a correspondingly designed gas turbine plant according to claim 7.

Gas turbine plants are composed essentially of a compressor, of a combustion chamber with a burner and of an expansion turbine. In the compressor, sucked-in air is compressed before it is mixed with fuel in the combustion chamber in the following burner arranged in the compressor plenum, and this mixture is burnt. The expansion turbine following the combustion chamber then extracts thermal energy from the combustion exhaust gases which have occurred in the burner and converts this into mechanical energy. A generator capable of being coupled to the expansion turbine can convert this mechanical energy into electrical energy for current generation.

Nowadays, gas turbine plants, like other current-generating plants, too, must have as low pollutant emissions as possible in all load ranges, while working at maximum efficiency. Major influencing variables are in this case the mass flows, set in the combustion chamber of the burner, of the fuel, of the compressed air and of the cooling air delivered for cooling the burner components. However, the limitation of pollutant emissions, in particular of NOx and unburnt fuel mostly in the form of CO, may lead to a minimization of the quantity of cooling air or of leakage air in the combustion chamber and consequently to parasitic flows which have an acoustically damping effect. Furthermore, under the boundary condition of limiting the emissions, an increase in efficiency usually also entails an increase in the volumetric heat release density in the combustion chamber. The two together, that is to say a reduction in acoustic damping and an increase in the heat release density in the combustion chamber, lead to a higher risk that thermoacoustically induced vibrations commence. However, thermoacoustic vibrations of this kind in the combustion chamber present a problem in the design and, in particular, in the operation of gas turbine plants.

To reduce such thermoacoustic vibrations, Helmholtz resonators, which are composed of at least one resonator tube and of a resonator volume, are employed nowadays for damping. Helmholtz resonators of this kind damp the amplitude of vibrations with the Helmholtz frequency in specific frequency ranges as a function of the cross-sectional area and the length of the resonator tube and of the resonator volume. Helmholtz resonators as damping devices for limiting thermoacoustic vibrations in combustion chambers are known, for example, from EP 1 605 209 A1 or U.S. 2007/0125089 A1.

FIG. 1 shows, for example, the arrangement, known from U.S. 2007/0125089 A1, of Helmholtz resonators 20 on a ring of the combustion chamber wall 10 transversely to the flow direction. The combustion chamber wall 10 is in this case of tubular form and separates the combustion chamber 1 from the surrounding compressor plenum 2. The perforations 22 in the combustion chamber wall 10 between resonator volume 21 and combustion chamber 1 form the resonator tubes of the Helmholtz resonators. In this case, as illustrated in FIG. 1, each Helmholtz resonator may have a plurality of resonator tubes or else only a single resonator tube. So that none of the hot combustion gases from the combustion chamber 1 are introduced into the Helmholtz resonators 20, additional ports for the delivery of barrier air are provided. In the exemplary embodiment shown in FIG. 1, these delivery ports 23 are arranged on that wall of the resonator volume 21 which lies opposite the resonator tubes 22. These ports 23 make it possible that compressed air S can flow out of the compressor plenum 2 surrounding the combustion chamber into the resonator volume 21 and from there, via the resonator tubes 22, into the combustion chamber 1, thus barring the penetration of hot combustion gases into the resonator tubes 22.

However, Helmholtz resonators with deliveries of barrier air via the volume body have the disadvantage that this barrier air flowing through the Helmholtz resonator can diminish its damping properties such that instabilities may occur when the burner is in operation. In particular, in such systems, even a marked reduction in the damping properties has been found with an increasing velocity of the barrier air flowing through the resonator tubes. However, a specific barrier air velocity in the resonator tubes is necessary in order to bring about a reliable barrier effect with respect to the combustion gases entering the resonator from the combustion chamber. Moreover, this type of delivery of barrier air makes it necessary to introduce from the compressor plenum a large fraction of air which, however, is then no longer available for actual combustion so as to reduce the flame temperature. This, in turn, in gas turbine plants operated at their power output limits for maximum NOx reduction, may bring about a rise in harmful NOx pollutants, although this is what is precisely to be avoided. Moreover, the cooler barrier air from the resonators may cause local instabilities in combustion to occur, thus leading in turn to increased CO pollutant emission.

The object of the invention is to provide a combustion chamber which overcomes the disadvantages described above.

This object is achieved by means of the combustion chamber having the features of claim 1.

Since a combustion chamber designed according to the preamble of claim 1 and having at least one Helmholtz resonator has at least one delivery port which is provided in a region of the combustion chamber wall near the resonator tube mouth of the at least one resonator tube and is oriented such that the barrier air flowing through the delivery port flows over the resonator mouth, the injection, known from the prior art, of barrier air through the Helmholtz resonator may be dispensed with. Its damping properties are therefore no longer influenced by the barrier air flowing through, with the result that reliable damping of thermoacoustic vibrations is achieved, thus ultimately lengthening the service life of the combustion chamber and therefore of the entire gas turbine plant. Moreover, with the barrier air delivery designed according to the invention, less air from the compressor plenum is required, as compared with the known versions, so that, overall, the NOx and CO pollutant emission of the gas turbine plant also becomes lower.

Further preferred exemplary embodiments may be gathered from the subclaims. What is essential in all the combustion chamber versions is that, with the aid of suitably designed delivery ports, a barrier film is built up in front of the resonator tube mouths on the combustion chamber side, and barrier air can thus be used more effectively as a reliable barrier against the inflow of hot combustion gases from the combustion chamber into the Helmholtz resonators, and at the same time the damping properties of the Helmholtz resonators are not influenced by the barrier air. Gas turbine plants equipped with such combustion chambers can thus have as low pollutant emissions as possible in all load ranges, while working at maximum efficiency.

The invention, then, will be explained by way of example by means of the following figures in which:

FIG. 1 shows diagrammatically a damping device known from the prior art,

FIG. 2 shows diagrammatically a first version according to the invention of a damping device,

FIG. 3 shows diagrammatically a second version according to the invention of a damping device,

FIG. 4 shows diagrammatically a third version according to the invention of a damping device,

FIG. 5 shows diagrammatically a fourth version according to the invention of a damping device.

Contrary to the known embodiment illustrated in FIG. 1, according to the invention the barrier air S is not routed through the damping device 20, but instead delivery ports 23′ and/or 23″ are provided and oriented in the combustion chamber wall 10 such that the barrier air S flowing through the delivery ports 23′, 23″ flows over the resonator tube mouth M in the region of the combustion chamber inner wall virtually in a similar way to film cooling.

FIG. 2 shows a first embodiment in which the resonator tube mouths M are set back in the combustion chamber wall 10 with respect to the combustion chamber inner wall 10′ in a defined area 10″ away from the combustion chamber inner space, and the delivery port 23′ is oriented such that the barrier air S is injected, virtually parallel to the flow direction of the combustion gases G, into the space between the area 10″ and the combustion chamber inner wall 10′ such that it flows completely over the setback resonator tube mouths M of the resonator tubes 22. In this space in front of these resonator tube mouths M (shown here only for two of the six resonator tubes), a barrier air film is thus formed which, even with a low mass flow of barrier air, very effectively prevents the penetration of hot combustion gases into the Helmholtz resonator 20. When injection of the barrier air takes place, as indicated in FIG. 2, through a tubular port 23′ in the upstream side wall in the downstream direction of the combustion gases, the injected barrier air is entrained by the stream of combustion exhaust gases and an especially effective barrier film is thus obtained.

Since the effective axial distance of film cooling bores is limited, a second delivery port 23″ lying opposite the first delivery port 23′ may be provided, as indicated in FIG. 3, which is oriented such that the barrier air S is injected virtually parallel to and opposite to the flow direction of the combustion exhaust gases G so that even resonators with a greater extent in the flow direction can still be barred effectively.

If, as indicated in FIG. 4, the combustion chamber wall 10 has on the setback area 10″, level with the combustion chamber inner wall 10′, an overlap L with the setback areas 10″, the extent of the resonators can likewise be increased, without an additional opposite row of barrier air bores being necessary.

It is advantageous if, as in FIG. 5, the delivery port 23′ or else other delivery ports, such as, for example, the delivery port 23″, shown in FIG. 3, is or are arranged in the combustion chamber wall 10 such that their axis A is inclined with respect to the resonator tube mouth M. As a result, as well as barring, additional impact cooling of the resonator wall is achieved, which may be expedient particularly in regions of the combustion chamber where an especially large amount of heat is introduced into the combustion chamber wall.

FIG. 2 to FIG. 5 show in each case various advantageous embodiments which individually or else in combination implement the idea according to the invention, to be precise that of ensuring an efficient and reliable barrier against the penetration of hot gases from the combustion chamber into the damping devices without the passage of barrier air via the damping device. Moreover, the invention also embraces embodiments in which, contrary to the exemplary embodiments shown, the deliveries of barrier air lie so near to the resonator tube mouths that they form a direct component of each of the resonator tube mouths and are thus virtually integrated into each resonator tube mouth.

Claims

1-6. (canceled)

7. A combustion chamber for a gas turbine plant, the combustion chamber includes:

a combustion chamber wall, through which combustion gases flow in a direction of a following gas turbine;

the combustion chamber wall having a damping device for the damping of thermoacoustic vibrations caused by combustion gases, the damping device comprising at least one Helmholtz resonator which is configured such that a resonator volume thereof lies on a side of the combustion chamber wall that faces away from an inner wall of the combustion chamber;

the resonator has at least one resonator tube, the tube co-operates with the resonator volume, and the resonator tube has a mouth lying opposite the resonator volume in the combustion chamber inner wall and exits into the combustion chamber;

at least one delivery port configured for entry of barrier air into the combustion chamber in such manner as for barring the resonator tube mouth the barrier air from a compressor plenum that surrounds the combustion chamber, the plenum being of a compressor that is positioned upstream of the combustion chamber, and the at least one first delivery port being provided in a region of the combustion chamber wall near the mouth of the at least one resonator tube and the at least one first delivery port being oriented such that the barrier air flowing through the at least one first delivery port flows over the resonator tube mouth;

the resonator tube mouth is set back in the combustion chamber wall with respect to the combustion chamber inner wall and into an area set back away from the combustion chamber, the at least one first delivery port is oriented and configured for injecting the barrier air virtually parallel to the flow direction of the combustion gases and flows over the setback resonator tube mouth.

8. The combustion chamber as claimed in claim 7, wherein the resonator comprises a plurality of resonator tubes and the resonator tubes have their respective mouths oriented such that the barrier air of the delivery port flows over the setback resonator tube mouths of the plurality of resonator tubes.

9. The combustion chamber as claimed in claim 8, further comprising a second one of the delivery ports directed opposite to the first one of the delivery ports, the second one of the delivery ports being oriented such that the barrier air through the second one of the ports is injected virtually parallel to and opposite to the flow direction of combustion gases in the combustion chamber and the barrier air through the second ones of the delivery ports flows over the setback resonator tube mouths.

10. The combustion chamber as claimed in claim 7, wherein the delivery port is oriented in the combustion chamber wall such that the delivery port axis is inclined with respect to the resonator tube mouth.

11. The combustion chamber as claimed in claim 7, wherein the combustion chamber inner wall has in a region of setback areas overlaps with the setback areas of the combustion chamber wall.

12. A gas turbine plant with a compressor for the compression of sucked-in air, with the combustion chamber as claimed in claim 7 following the compressor; and

the plant having a burner for admixing fuel and for the combustion of the fuel/air mixture, and an expansion turbine which follows the burner and which converts the combustion exhaust gases of the burnt fuel/air mixture into mechanical energy.