AU2010233724B2

AU2010233724B2 - Combustion chamber having a helmholtz damper

Info

Publication number: AU2010233724B2
Application number: AU2010233724A
Authority: AU
Inventors: Fulvio Magni; Dariusz Nowak; Adrian Schneider; Martin Andrea Von Planta
Original assignee: General Electric Technology GmbH
Current assignee: General Electric Technology GmbH
Priority date: 2009-04-11
Filing date: 2010-04-09
Publication date: 2015-06-18
Anticipated expiration: 2030-04-09
Also published as: WO2010115980A3; AU2010233724A1; CH700799A1; EP2417394A2; MY160094A; WO2010115980A2; EP2417394B1

Abstract

The invention relates to a combustion chamber (16) for a gas turbine (10), wherein at least one Helmholtz damper (30) is arranged. The combustion chamber comprises a number of burners or is equipped with a combination of burners (14, 15). The Helmholtz damper (30) is designed according to an individually determined or predetermined damping requirement against the thermoacoustic oscillation frequencies occurring in the combustion chamber and is arranged inside the disposed burners (14, 15) or in place of a free available space inside the combination of burners.

Description

-1 Combustion chamber having a Helmholtz damper Technical field 5 The present invention relates to a combustion chamber for a gas turbine. Prior art 10 The solution to the problem relating to the thermoacoustic oscillations in modern low-NOr combustion chambers of gas turbines is becoming ever more important. The prior art has therefore variously proposed the arrangement of so-called Helmholtz dampers 15 on the combustion chamber of a gas turbine, which Helmholtz dampers are able to dampen effectively specific oscillation frequencies in the combustion chamber as a result of their configuration where a damping volume is connected to the combustion chamber via a thin connection channel. 20 Since the frequency and amplitude of thermoacoustic oscillations occurring in a combustion chamber are affected by the very different geometric and operational parameters of the combustion chamber, the expected oscillations in a new combustion chamber 25 can only be predicted with much difficulty, and these predictions may be incomplete. Hence, it may be that the Helmholtz dampers used on the combustion chamber are not ideally tuned to the actually occurring oscillations in the combustion chamber, particularly if these combustion chambers have to cover a broad 30 range of operating conditions. Hence EP-A1-0 597 138 for example has proposed to design the Helmholtz dampers in a wholly or partly replaceable fashion in order to be able to undertake retrospective changes in the 35 spectrum of the occurring - 2 - B09/049-0 resonant frequencies. To this end, a so-called manhole has been proposed as a measure in the turbine housing, through which manhole the Helmholtz dampers can be replaced. 5 A disadvantage herein is that, firstly, the tuning to a resonant frequency can only take place in steps, that replacing damper parts or whole dampers is very complicated and that there must regularly be 10 significant constructive expenditure on the turbine housing and on the combustion chamber itself for the purpose of the replacement. Furthermore, the prior art has disclosed document 15 EP 02 782 607.2, which demonstrates how a Helmholtz damper is installed in a combustion chamber. The final purpose here consists of embodying the Helmholtz damper such that the damping frequency thereof is adjustable, and more particularly continuously adjustable. This 20 allows simple matching of the damping to the thermoacoustic behavior in the combustion chamber and corresponding optimization thereto. There is no need to replace parts of the dampers or whole dampers in this case and so access options with a correspondingly large 25 design can be dispensed with. At the same time, the adjustability of the Helmholtz dampers removes the necessity of producing and keeping available differently configured dampers or damper parts for different resonant frequencies. 30 Installing these Helmholtz dampers is linked to a combustion chamber of a gas turbine that is operated with a newer generation of premix burners. Here, these Helmholtz dampers are provided on the entry side of the 35 combustion chamber, which may, for example, be embodied with two rings of premix burners and adjustable Helmholtz dampers arranged therebetween. The gas turbine itself is surrounded by a gas-turbine housing, within which there is a plenum filled with compressed -3- B09/049-0 air. The plenum surrounds the combustion chamber, which is separated from the plenum by a combustion-chamber housing. The arrangement of the combustion chamber within the gas turbine is substantially the same as 5 described in the document EP-A1-0 597 138, mentioned at the outset. Within the combustion-chamber housing, the combustion chamber is delimited on the entry side by a front cover. The combustion chamber moreover has an annular design and is equipped with the aforementioned 10 premix burners, as are, for example, described in the basis property rights EP-0 321 809 Al or EP-0 704 657 Al, and the developments following on from these, with all documents here constituting an integral component of this application. 15 The premix burners are arranged in corresponding openings in the front cover and open into the combustion chamber. Helmholtz dampers are provided between the burners for damping the thermoacoustic 20 oscillations excited in the combustion chamber during the combustion process. These Helmholtz dampers each have a damping volume that is composed of a fixed cylindrical and a variable cylindrical damping volume. The damping volume is connected to the combustion 25 chamber via a comparatively narrow connection channel. The arrangement of connection channel and damping volume forms a damping resonator, the resonant frequency of which is determined, inter alia, by the size of the damping volume. 30 Such a configuration clearly shows that such an installation of the Helmholtz dampers between the premix burners requires a relatively large amount of space within the annular combustion chamber, which can 35 necessarily lead to a certain amount of narrowing in the design and arrangement of the premix burners. The fact that both installation and removal of such Helmholtz dampers is interdependent on those of the premix burners must not be misjudged either, and so the -4 originally provided arrangement between premix burners and Helmholtz dampers can no longer simply be changed at a later point in time. This results in restrictions that, individually in respect of the respective requirements when operating the 5 combustion chamber, impede measures being taken in a quick and targeted fashion for preventing the occurrence of thermoacoustic oscillations, or do not sufficiently satisfy these. Summary of the invention 10 The invention seeks to address at least one problem of the above prior art. It is desirable to design the embodiment of a Helmholtz damper of the type mentioned at the outset such that it can be used in diverse fashions according to requirement, space 15 and number without basic reconstructions on the combustion chamber and such that a simple adjustment option for the dampings to be obtained in each case is provided. In accordance with a first aspect of the present invention, there 20 is provided a combustion chamber for a gas turbine, with at least one Helmholtz damper arranged on the combustion chamber, wherein the combustion chamber is equipped with a number of burners or a combination of burners, and wherein the Helmholtz damper is arranged within the disposed burners or in place of a free, 25 available space within the combination of burners according to a respectively determined or established damping requirement to counter the thermoacoustic oscillation frequencies occurring in the combustion chamber, wherein the Helmholtz damper has means that allow at least one of lateral adjustment and elongation with 30 respect to the original longitudinal axis, the means including an intermediate flange, providing a fixed-point mount for the Helmholtz damper, the intermediate flange being directly connected to an outer shell of the Helmholtz damper, wherein the outer shell is operatively connected to an adjustment piston 35 placed approximately in the longitudinal center of the Helmholtz damper.

-4a The significant advantages of the invention can be seen in the fact that the Helmholtz damper designed according to the invention can be inserted in place of a spatially separated premix burner of the known type. In particular, reference should 5 be made to the fact that advances in premix combustion in annular combustion chambers have recently allowed the use of premix burners, the number of which required for the same power is less than the number of originally provided premix burners, and so a few burner positions are no longer required in the case of such 10 repowering of the annular combustion chamber and hence the position freed by this is also available. Hence, this leads to an unanticipated option of being able to use the free or newly freed burner positions for installing the 15 Helmholtz dampers according to the THE NEXT PAGE IS PAGE 5.

- 5 - B09/049-0 invention, without having to accept disadvantages in respect of the combustion chamber operating concept. A further advantage of the invention can be seen in the 5 fact that the precise arrangement of the Helmholtz damper can be optimized by means of a thermoacoustic simulation carried out in advance, bearing in mind that there now are enough adjustment variations available, and so there are no restrictions in any form during the 10 installation of such a Helmholtz damper, neither in respect of the number nor in respect of the position to be assigned within a combination of premix burners. Accordingly, these Helmholtz dampers can be installed without problems at those points where they also 15 provide a maximized damping effect because if even only a single Helmholtz damper is positioned incorrectly this may easily result in the lack of a satisfactory effect overall. 20 A further advantage of the invention can be seen in the fact that the prescribed spatial conditions can be used in an optimum fashion by a maximum damping volume by virtue of the Helmholtz damper according to the invention proposing that provision is not made for a 25 tuning pipe placed out in front, as is usually the case, but rather for letting it project deep into the damping volume, which has a positive effect on the spatial conditions for the installation. 30 A further advantage of the invention can be seen in the fact that the exposed positioning of the Helmholtz damper remedies measures to counter the thermal load acting there. These measures consist of firstly providing efficient impingement cooling that cools the 35 front surface of the Helmholtz damper. For this purpose, the Helmholtz damper is equipped with a special transition piece with radial air-supply bores through which the coolant is supplied.

-6 A further significant advantage of the invention can be seen in the fact that the Helmholtz damper is completely accessible directly from the outside, without having to uninstall or remove any covers, for the purpose of adjusting the frequency. 5 A further advantage of the invention can be seen in the fact that the Helmholtz damper is embodied such that, within the combustion chamber, it not only has axial flexibility in relation to the other different components, but it is also provided with lateral 10 compliance such that there is no space-related restriction during installation, and said Helmholtz damper is otherwise also compliant during operation. Brief explanation of the figures 15 In conjunction with the drawings, the invention will be explained in more detail below on the basis of an exemplary embodiment. All elements that are not required for the direct understanding of the invention have been omitted. Equivalent elements have been 20 provided with the same reference signs in the various figures. In detail: Figure 1 shows a configuration of premix burners with an installed Helmholtz damper according to the prior art; 25 Figure 2 shows a Helmholtz damper according to the invention installed in place of a premix burner; Figure 3 shows a Helmholtz damper according to the invention 30 installed between two premix burners; - 7 - B09/049-0 Figure 4 shows the front part of the Helmholtz damper with cooled front surface and tuning pipe; and 5 Figure 5 shows a section through the rear part of a Helmholtz damper according to the invention. Ways of implementing the invention 10 Figure 1 shows, in a sectional view, a cross section of the entry side of the combustion chamber of a gas turbine with, as already mentioned above, two rings of double-cone burners and, arranged therebetween, an 15 adjustable Helmholtz damper as per an embodiment that is part of the prior art. The gas turbine 10 is enclosed by a gas-turbine housing 11, within which there is a plenum 12 that is filled with compressed air. The plenum 12 surrounds the combustion chamber 16, 20 which is separated from the plenum 12 by a combustion chamber housing 13. The arrangement of the combustion chamber 16 within the gas turbine 10 is substantially the same as described in the document EP-Al-0 597 138, mentioned at the outset. Within the combustion-chamber 25 housing 13, the combustion chamber 16 is delimited on the entry side by a front cover 26. The combustion chamber 16 has an annular design and is equipped with so-called premix burners 14, 15; the applicant calls these EV burners or AEV burners, and these are well 30 known in the art and are arranged in rings about the axis of the gas turbine, as disclosed in EP-Al-0 597 138 or in EP 0 976 982 B1, particularly in figure 2. 35 The premix burners 14, 15 are arranged in corresponding openings in the front cover 20 and open into the combustion chamber 16. In order to damp the thermoacoustic oscillations that are excited in the combustion chamber 16 during the combustion process, - 8 - B09/049-0 provision is made for Helmholtz dampers 17 situated between the rings with the burners 14, 15. These Helmholtz dampers 17 have a damping volume that is composed of a fixed cylindrical and a variable 5 cylindrical damping volume. The damping volume is connected to the combustion chamber 16 via a comparatively narrow connection channel 18. The arrangement of connection channel 18 and damping volume forms a damping resonator, the resonant frequency of 10 which is determined, inter alia, by the size of the damping volume, with this connection channel 18 being directly connected to the combustion chamber. Installing such a Helmholtz damper requires an installation structure, determined in advance, and this 15 leads to fixed positioning of the Helmholtz damper. Figure 2 shows an identical initial configuration of the combustion chamber 16 as in figure 1. The original premix burner 15 from figure 1 is replaced by a 20 Helmholtz damper 30 according to the invention. Here, this Helmholtz damper 30 is designed such that it can accordingly be replaced by a premix burner. In respect of this implementation, the Helmholtz damper 30 and can be radially guided in the front plate already present 25 there and can be installed, axially freely, therein, as a result of which this installation no longer requires a special installation structure. The special embodiment of this Helmholtz damper 30 will be described in more detail in the description of figures 30 4 and 5. A further option for installing such a Helmholtz damper 30 is explained in more detail in figure 3. Here the Helmholtz damper 30 may, thanks to its thin embodiment, 35 even be installed between two premix burners 14, 15 within the annular combustion chamber, i.e. always wherever a thermoacoustic simulation carried out in advance supplies corresponding information. Accordingly, such a configuration allows the greatest - 9 - B09/049-0 amount of flexibility when positioning the Helmholtz damper 30 within a combination of premix burners, with the same also holding true should provision be made for diffusion burners in place of premix burners. 5 The Helmholtz damper can then be inserted, and the frequency thereof can be set, without difficulties from the outside if a corresponding opening is provided in the gas-turbine housing 11, as indicated in figure 3. 10 This can moreover allow individual regulation of the Helmholtz damper 30 from the outside. By way of example, the Helmholtz damper 30 can be anchored within the combustion-chamber housing 13 by using the already available mounting structure for the premix burners. 15 Figure 4 shows the front part 30a of the installed Helmholtz damper 30; here it can be seen that a tuning pipe 31 is arranged on the inside. This allows a very flexible design of the length of such a tuning pipe 31, 20 which is so important in terms of the effect, because the available space within the pipe length 30a is, in principle, large enough such that there is no need for the tuning pipe 31 to be arranged out in front, as is conventional, but rather it can, internally, project 25 deep into the damping volume 35. In such an embodiment work can also be undertaken with a front surface 32, which is operated by a cooling system, such that the adjacent tuning pipe 31 and the surrounding damping volume 35 are optimally protected against the thermal 30 loads from the combustion-chamber space. The coolant 33 itself flows into the interior of the damping volume 35, via a transition piece 34 and radial or quasi radial openings 33a applied therein, in the direction of the front surface 32 of the Helmholtz damper 30, 35 with the front surface 32 preferably being cooled by efficient impingement cooling. The thermally exhausted coolant then flows away from the front surface 32 on the front side, as can be seen from the illustrations in figures 2 and 3. In principle, the damping volume 35 - 10 - B09/049-0 is selected such that the damping frequency thus obtainable is in the vicinity of the frequency of one of the thermoacoustic oscillations expected in the combustion chamber. What the implementation of a tuning 5 pipe 31 provided by the design described in more detail here brings about is that, in the case of a gas turbine to be newly put into operation, the design of this tuning pipe 31, in terms of the diameter, the wall thickness and the length thereof, allows precise tuning 10 of the Helmholtz dampers 30 to the occurring oscillation frequencies and thus the obtainment of optimal damping by the smallest means. This is supplemented by the fact that a thermoacoustic simulation carried out in advance makes it possible to 15 determine the optimum installation position. However, this option is only possible if the installation specifications in respect of a Helmholtz damper 30 as per figures 2 and 3 can also be satisfied. 20 Thus, on the one hand, the thermoacoustic simulation determines the optimum installation position; on the other hand, more precise tuning to counter thermoacoustic oscillations can be obtained by the proposed design. These instances of tuning, which can 25 be implemented individually or, together, in combinations, make it possible to cover the very different oscillation frequencies by a single embodiment of a Helmholtz damper 30; this avoids the necessity of also having to use a combination of 30 differently dimensioned Helmholtz dampers in order to dampen different oscillation frequencies. Figure 5 shows the rear partial section 30b of the Helmholtz damper 30, with two further advantages of the 35 system being referred to as a consequence. On the one hand, a further possible adjustment of the damping volume 35 is provided here by, in particular, embodying this adjustment such that it can be carried out in the installed state of the Helmholtz damper 30, as - 11 - B09/049-0 illustrated in figures 2 and 3. To this end, the end side damping volume 35 is provided with a termination sleeve 36, which serves for end-side mounting and guiding of a piston rod 37. In the damping volume 35, 5 this piston rod 37 is connected to an adjustment piston 38, which encompasses the clear width of the damping volume 35. The displaceability of the adjustment piston 38, which causes a change in the volume of the active damping volume 35, is brought about by the displacement 10 of the aforementioned piston rod 37 in an operatively connected fashion with an adjustable clamped joint 39 or by other means. This provides an additional component that, firstly, can be used on the turbine housing without significant provisions and, secondly, 15 allows direct fine adjustment of the active damping volume when necessary, particularly if this is the damping property in the case of transient load ranges of the gas turbine, in which damping correction becomes necessary against unforeseen thermoacoustic 20 oscillations in the combustion chamber. Secondly, the Helmholtz damper 30 has a lateral adjustment option, which was found to be very advantageous during installation or operation. To this 25 end, provision is made for a flange 40, which is visible in figures 2 and 3 and ensures that there is a fixed-point mount 41 for the Helmholtz damper 30. This intermediate flange 40 is directly operatively connected to an outer shell 42 of the Helmholtz damper 30 30. This outer shell 42 ensures that lateral extensions are held, operatively connected with an adjustment piston 43 placed approximately in the longitudinal center of the Helmholtz damper 30. The intermediate flange 40 is preferably arranged in the region of the 35 front section of the combustion-chamber housing 13 and anchored there; this emerges analogously from figures 2 and 3.

- 12 - B09/049-0 After all this, this allows, with minimized complexity, optimal matching of the damping properties of the utilized Helmholtz dampers 17 to the thermoacoustic oscillations actually occurring in the adjustment 5 chamber 16 during the operation, should an additional necessity arise, and this is made possible without having to revert to covering the gas-turbine housing 11.

- 13 - B09/049-0 List of reference signs 10 Gas turbine 11 Turbine housing 12 Plenum 13 Combustion-chamber housing 14 Burner, premix burner 15 Burner, premix burner 16 Combustion chamber 17 Helmholtz damper according to the prior art 18 Connection channel 19 Access opening 20 Front cover 30 Helmholtz damper 30a Front part of the Helmholtz damper 30b Rear part of the Helmholtz damper 31 Tuning pipe 32 Front surface, cooled 33 Coolant 33a Openings for coolant to flow in 34 Transition piece 35 Damping volume 36 Termination sleeve 37 Piston rod 38 Adjustment piston 39 Clamped joint 40 Flange 41 Fixed-point mount 42 Outer shell 43 Adjustment piston

Claims

1. A combustion chamber for a gas turbine, with at least one Helmholtz damper arranged on the combustion chamber, wherein the combustion chamber is equipped with a number of burners or a combination of burners, and wherein the Helmholtz damper is arranged within the disposed burners or in place of a free, available space within the combination of burners according to a respectively determined or established damping requirement to counter the thermoacoustic oscillation frequencies occurring in the combustion chamber, wherein the Helmholtz damper has means that allow at least one of lateral adjustment and elongation with respect to the original longitudinal axis, the means including an intermediate flange, providing a fixed-point mount for the Helmholtz damper, the intermediate flange being directly connected to an outer shell of the Helmholtz damper, wherein the outer shell is operatively connected to an adjustment piston placed approximately in the longitudinal center of the Helmholtz damper.

2. The combustion chamber as claimed in claim 1, wherein the Helmholtz damper has a damping volume, in that an internal tuning pipe is arranged in a front part of the damping volume.

3. The combustion chamber as claimed in claim 1 or 2, wherein the Helmholtz damper has a damping volume, in that an adjustment device acting on the size of the damping volume is arranged in a rear part of the damping volume.

4. The combustion chamber as claimed in any one of claims 1 to 3, wherein the burners are premix burners.

5. The combustion chamber as claimed in claim 1, wherein the combustion chamber is an annular combustion chamber, and wherein the burners are arranged over one or more rows on the front cover. -15

6. The combustion chamber as claimed in claim 1, wherein the Helmholtz damper is inserted in place of a burner.

7. The combustion chamber as claimed in claims 1 or 5, wherein the Helmholtz damper is inserted between two existing burners.

8. The combustion chamber as claimed in any one of the preceding claims, wherein the damping volume of the Helmholtz damper can be adjusted continuously from the outside.

9. The combustion chamber as claimed in any one of the preceding claims, wherein a front surface to the combustion chamber is cooled, which front surface belongs to the Helmholtz damper.

10. The combustion chamber as claimed in claim 9, wherein cooling is brought about by impingement cooling.

11. The combustion chamber as claimed in any one of the preceding claims, wherein at least one of the following is/are determined by thermoacoustic simulation that was carried out in advance: (a) site for installing the Helmholtz, (b) damping volume to be provided, and (c) geometric design of the tuning pipe. ALSTOM TECHNOLOGY LTD WATERMARK PATENT AND TRADE MARKS ATTORNEYS P37628AU00